Guess the confusion also stem from Toyota FSM in the fix directives.
The fix flow chart states that after a check and the result comes out bad, then change or fix something. What it didn't state was after a check and the result comes out good then do the monitor or trip detection logic test to see if the code is gone before moving on to next check.
A novice would probably follow the whole check steps to the end like the FSM instructed and that would mean ending up at timing chain or camshaft (step5) without even checking if the problem has already been fixed at step 1-3, like you rightly pointed out that we would do this test as many times as we concluded each of the steps.

I have watched the Hall effect video and yes the CMP sensor is the brain box to tell us the condition of the timing chain, because if we had a slacked chain or jumped tooth/timing or electrical problems, then the CMP sensor will not read correctly using its electro magnetic field and therefore the ECU/PCM would report a P0340 DTC.

I have reved the engine above 600 RPM many times, and also that engine has been cranked (start/off) more than 10 times. Also after driving a journey of 4hrs I guess the CMP sensor temperature would have been more than 50-100 degrees Celsius and obviously that should have set a P0340 DTC if the sensor resistance at that temperature was intolerant.

I need your directives on P1135, P1155 and P0161. I am thinking of getting all the sensors out and look at them critically to make sure they are the correct sensors and part numbers, or just doing a resistance/voltage/continuity tests enough. I was only able to see the part number on the denso sensor on bank 1 sensor 1 (89465-20790)

olaboy1:
Guess the confusion also stem from Toyota FSM in the fix directives.
The fix flow chart states that after a check and the result comes out bad, then change or fix something. What it didn't state was after a check and the result comes out good then do the monitor or trip detection logic test to see if the code is gone before moving on to next check.
A novice would probably follow the whole check steps to the end like the FSM instructed and that would mean ending up at timing chain or camshaft (step5) without even checking if the problem has already been fixed at step 1-3, like you rightly pointed out that we would do this test as many times as we concluded each of the steps.

I have watched the Hall effect video and yes the CMP sensor is the brain box to tell us the condition of the timing chain, because if we had a slacked chain or jumped tooth/timing or electrical problems, then the CMP sensor will not read correctly using its electro magnetic field and therefore the ECU/PCM would report a P0340 DTC.

I have reved the engine above 600 RPM many times, and also that engine has been cranked (start/off) more than 10 times. Also after driving a journey of 4hrs I guess the CMP sensor temperature would have been more than 50-100 degrees Celsius and obviously that should have set a P0340 DTC if the sensor resistance at that temperature was intolerant.

I need your directives on P1135, P1155 and P0161. I am thinking of getting all the sensors out and look at them critically to make sure they are the correct sensors and part numbers, or just doing a resistance/voltage/continuity tests enough. I was only able to see the part number on the denso sensor on bank 1 sensor 1 (89465-20790)

In a couple of hours, we should be with you!

Then we can start.

Tunde783

So back to your Lexus

P0016,P0019, P0021 and P0025 are related.

The first two deal with the crankshaft (CKP)

The last two deal with the camshaft (CMP)

This video explains how they work in your engine:
https://www.youtube.com/watch?v=GlK9U-ox0PE

In effect, the most critical codes right now are these:
1. P0016,P0019, P0021 and P0025

Followed by
2. P0300 - P0306 AND P0352,P0354,P0356

and then
3. P0441 and P0455


What is the correlation between the PCM/ECU (or as Lexus calls it the ECM) and these?


In the VVT system, the appropriate intake and exhaust valve open and close timing is controlled by the ECM. The ECM performs intake and exhaust valve control by performing the following:

1) controlling the camshaft and camshaft oil control valve, and operating the camshaft timing gear; and

2) changing the relative positions of the gaps between the camshaft and crankshaft.

In some vehicles, this is controlled by hydraulics, in your Lexus, this is controlled by electronics.

Why did your ECM detect that is a problem and set the code P0016?

It discovered a deviation in crankshaft position sensor signal and VVT sensor 1 (for intake camshaft [bank 1]) signal (2 trip detection logic)

Why did your ECM detect that is a problem and set the code P0019?
It discovered a deviation in crankshaft position sensor signal and VVT sensor 2 (for exhaust camshaft [bank 2]) signal (2 trip detection logic)

How did your ECM come to this conclusion in both instances?

We hope that you have read the earlier posts. It used a monitor.

To monitor the correlation of the intake camshaft position and crankshaft position, the ECM checks the VVT learning value while the engine is idling.

The VVT learning value is calibrated based on the camshaft position and crankshaft position.

The intake valve timing is set to the most retarded angle while the engine is idling. If the VVT learning value is out of the specified range in consecutive driving cycles, the ECM illuminates the MIL and sets the DTC P0016 (Bank 1) or P0018 (Bank 2).

To monitor the correlation of the exhaust camshaft position and crankshaft position, the ECM checks the VVT learning value while the engine is idling.

The VVT learning value is calibrated based on the camshaft position and crankshaft position. The exhaust valve timing is set to the most advanced angle while the engine is idling.

If the VVT learning value is out of the specified range inconsecutive driving cycles, the ECM illuminates the MIL and sets the DTC P0017 (Bank 1) or P0019 (Bank 2).

How do you get out of this mess?

Mechanical - (timing chain has jumped tooth or chain stretched)
Electrical - Replace ECM

But you said you recently did an engine overhaul, so the culprit is not the ECM!

Then most likely what you have got on your hands is an engine rebuild gone wrong.

Hopefully it is not so bad that it cannot be resolved.

The competence of the engine rebuild shop you used ought to be questioned. If he is not a Lexus certified mechanic (good luck finding that in Nigeria by the way) did they follow the Factory Service Manual in performing the repair?

This vehicle has a 2GR-FE engine.

Here is what Wikipedia has to say about it:

The 2GR-FE is a 3.5 L (3456 cc) version for transverse FWD, 4WD, or AWD mounting.[1] Bore remains at 94 mm but stroke is reduced to 83 mm. Reported output varies depending on the vehicle application, but is approximately 268 hp (200 kW) to 296 hp (221 kW) at 6200 rpm with 248 lb·ft (336 N·m) to 260 lb·ft (353 N·m) of torque at 4700 rpm on 87 octane (R+M/2).[2] This version features Toyota's Dual VVT-i, variable valve timing on both the intake and exhaust cams. The cams are driven using a timing chain.

Valves are driven by roller-follower rocker arms with low friction roller bearings, and a unique, concave cam lobe design to increase valve lift over the traditional shimless lifter type system of the 1GR-FE. This increases overall cylinder head height to accommodate the slightly taller roller rocker system. Moreover, the cylinder head is segmented into 3 parts: valve cover, camshaft sub-assembly housing, and cylinder head sub-assembly. As such, this valvetrain is used across all other GR engines with Dual VVT-i. Its service weight is 163 kg.

Source: https://en.wikipedia.org/wiki/Toyota_GR_engine#2GR-FE

Note:

The bolded indicates that this is not a job for the average joe. You don't want your engine to be someone's experimental ground whose experience with changing timing is limited to non-VVT motors. Either you go to a Toyota/Lexus shop or to an knowledgeable independent shop familiar with this sort of repairs.

So you have most likely got either of the following:

1. a wrongly installed timing chain
2. a failed VVTi actuator
3. damaged wiring to the VVTi actuators

We believe it is more likely going to be number 1.

By the way, there is a Lexus TSB that says that if have P0016 and or P0019 as well as P0300 to P0306, ignore P0300 to P0306 and fix the P0016 and or P0019 first and the P0300 to P0306 might go!

Don't you think that you should get a copy of the Factory Service Manual for this ride?


As per the recommendation by a fellow Lexus user below:

Yes, I have service manuals for all 3 of our vehicles, two of which are Lexus. My feeling is that you don’t have to be a mechanic to benefit considerably from the information. By knowing how the vehicle is constructed, the component names and of course the procedures to diagnose and repair various systems you’re in a better position to work with your service provider. And if you decide to do the work yourself you have the instructions to help you do the job the way the manufacturer specifies.

Generally automotive service manual content is addressed to service technicians who are proficient with the tools of the trade. And as you might expect you will probably need to come up to speed on some manufacturer-specific acronyms and jargon before you will get the most from them. Fortunately Toyota service manuals are organized similarly so that if you become familiar with one the learning curve is easier for the next.

A way to determine if manuals would be a good investment for you is to go to the Toyota technical information site: http://www.techinfo.toyota.com and buy 2-day standard access to service publications for $15.

We would highly recommend that you do.
You have spent much, and are going to spend some more.
It will help you determine who is worth your money!

Great breakdown on the Lexus problem, and how you zero down the problems to 3 culprits in the right order of repair.
The FSM is such a resourceful material if you want to run your vehicle at 100% optimal level. From buying the right spare parts and following manufacturer's recommended service intervals.

olaboy1:
Great breakdown on the Lexus problem, and how you zero down the problems to 3 culprits in the right order of repair.
The FSM is such a resourceful material if you want to run your vehicle at 100% optimal level. From buying the right spare parts and following manufacturer's recommended service intervals.

Thank you

olaboy1

P0161 - Study m_05_0007, m_05_0018, m_05_0057
P1135 - Study m_05_0098
P1155 - Study m_05_0098

Actual diagnosis is for tomorrow

Ok cool. Since the DTC's are neither fuel trim nor misfire malfunction, then all 3 are number one priority and would be looked into at the same time. Looks like my mechanic is more a mechanical guy who only reads code and just change part, he doesn't seem to be interested in freeze frame data.
The freeze frame data is very crucial to this diagnosis as it especially reveals if the air-fuel ratio was lean or rich etc
Tomorrow I like you to also explain what it means for the ECM to enter fail safe mode.

olaboy1:
Ok cool. Since the DTC's are neither fuel trim nor misfire malfunction, then all 3 are number one priority and would be looked into at the same time. Looks like my mechanic is more a mechanical guy who only reads code and just change part, he doesn't seem to be interested in freeze frame data.
The freeze frame data is very crucial to this diagnosis as it especially reveals if the air-fuel ratio was lean or rich etc
Tomorrow I like you to also explain what it means for the ECM to enter fail safe mode.

Your welcome! Till tomorrow!! We will look into the highlighted!!!

1. All three are number 1 priority- Yes, you are right because they have put your ECU in fail-safe mode!

2. Freeze Frame Data - we will go through that together

3. ECU in fail-safe mode - "Fail safe mode is the computer in your car trying to minimize or prevent serious damage by altering transmission shift, engine RPM or engine load conditions" according to repairpal.com website.

More about the fail-safe mode here: http://www.rhinopower.org/Tech/limp.html

Now can you see why you are complaining that the vehicle is driving strangely, the vehicle is actually trying to prevent its self-destruction or you being the agent of such destruction by driving in a way that is out of tune with the parameters it has at its disposal.

The brain of the vehicle is the ECU, just like the brain can cause your body to have a "fever as a natural bodily defense against infection" according to webmd.com, same thing your vehicle is responding to the lack of signals from the upstream and downstream oxygen sensors.

So, let's get started.

My findings so far. The FSM directive for the terminals is too dodgy for a beginner, as I don't understand if I am troubleshooting from the wire harness connector to the sensor or I need to go into ECM/ECU. I need you to break it down better for me. I can't say if I have done the electrical troubleshooting for all areas correctly but so far my findings below.

Bank 1 sensor 1 A/F sensor is the wrong sensor for that location, the one with DTC P1135. The resistance is 12.8ohms, the Toyota FSM wouldn't say what's the right ohms, but Bank 2 sensor 1 came out as 1.2ohms and that seem to be the right ohms reading for upstream oxygen sensors. So I guess a downstream sensor was used to replace an upstream sensor base on the ohms reading below. Resistance checks for the oxygen sensors were very straight forward, where I have difficulties trying to follow the FSM are continuity, short, voltage and wire harness resistance tests.

Resistance for sensors
Bank 1 sensor 1: 12.8ohms
Bank 2 sensor 1: 1.2ohms
Bank 1 sensor 2: 14.4ohms
Bank 2 sensor 2: 13.8ohms

Resistance for wire harness
Waiting for further directives.

Continuity
For continuity test I grounded the negative lead of my digital multimeter to a good ground, and used the positive lead to touch all the four pins in ONE sensor with ignition off and no beep. I repeated same process for all the 4 sensors no beep, went further to do same for all the 4 wire harness connector pins (16pins), and 3 wire harnesses came back with no beep except for the wire harness of bank 2 sensor 1 (P1155) that beeped. So tell me if I have done the continuity tests wrongly.
Bank 1 sensor 1: no beep
Bank 2 sensor 1: no beep
Bank 1 sensor 2: no beep
Bank 2 sensor 2: no beep
Bank 1 sensor 1 wire harness: no beep
Bank 2 sensor 1 wire harnesss: BEEP
Bank 1 sensor 2 wire harness: no beep
Bank 2 sensor 2 wire harness: no beep

Voltage tests
Also need more clarification to know if I have done the voltage tests correctly. With the ignition key set to ON without starting the car, I put my negative and positive DMM pins on 1 and 2 upper pins in the wire harness, I did not measure voltage for the sensors because they function at at around 600 degrees Fahrenheit.
Bank 1 sensor 1: not measured
Bank 2 sensor 1: not measured
Bank 1 sensor 2: not measured
Bank 2 sensor 2: not measured
Bank 1 sensor 1 wire harness: 11.9v
Bank 2 sensor 1 wire harness: 0v
Bank 1 sensor 2 wire harness: 0v
Bank 2 sensor 2 wire harness: 11.9v

Short
I haven't measured for short, I need more guidance as I don't quite understand the FSM.
NOTE: the two fans came on once I put the AC on and the AC works very fine and chilly.
I am attaching the dashboard pix with no temperature screen meter, my mechanic said this car uses dashboard light to show if the car is overheating.

See dashboard pixs

olaboy1:
See dashboard pixs

We will work into this in a few hours time - say about 9pm Nigerian time.

Busy plus - laptop battery running low

AutoElectNG:


We will work into this in a few hours time - say about 9pm Nigerian time.

Busy plus - laptop battery running low

That's not a problem. Take your time

olaboy1:


That's not a problem. Take your time

11:12pm On Mar 20, 2017 post above updated, and the three questions that you asked have been treated!!

AutoElectNG:


11:12pm On Mar 20, 2017 post above updated, and the three questions that you asked have been treated!!

Good I am paying attention in this tutorials.
It's very nice the car can enter fail safe mode to avoid further destruction. I hope it was able to keep my CAT from failing and maybe that's why I haven't got any CAT threshold DTC.
The content files in my FSM are not opening so it's very hard to get to the right info I need in it.
I will need info from the FSM on sensor oem part number, table of fuses and relays and what they control should I need to check all the fuses and relays controlling the sensors.

According to the manual

All three DTCs cause the PCM/ECU to turn off the heater circuit in which there is an abnormality. The circuit will be turned on again once the ignition switch is off

DTC No.
P0161/29
P1135/21
P1155/28

You may notice that there are two more digits after the 5 digit DTC.

The first of the two characters in the symptom code is the category number. This pertains to general category of the fault.

What does the 2 stand for? 2 is for frequency pulse width modulated failure.

The second of the two-character code is the subtype character.

21 and 28 Stands for Oxygen sensor signal/oxygen sensor heater signal open or short in oxygen sensor or oxygen sensor signal

Could not find a reference to 29, so the question is was 29 a mistake, should it have been 28?

In what subsystem does the PCM/ECU detect that there is a problem?

Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

When the heater operates, heater current exceeds 2A. The PCM/ECU uses a two trip detection logic to verify the presence of this fault

OR

Heater current of 0.2A or less when the heater operates. The PCM/ECU uses a two trip detection logic to verify the presence of this fault

Where should we narrow down as the trouble area to diagnose and resolve this problem?

This DTC could be caused by

1. an open or short in heater circuit of oxygen sensor
2. Oxygen sensor heater
3. ECM

Do you have a multi-meter?

Do you know how to use it?

Can you easily access your ECM?

Because the first test is to rule out a faulty ECM!

If you do, then do test 1(b) and 1(c) and report the results!

But be sure that your multi-meter leads are connected to the appropriate pins at the ECM so as not to read false results!

olaboy1:
See dashboard pixs

Noted.

AutoElectNG:
Do you have a multi-meter?

Do you know how to use it?

Can you easily access your ECM?

Because the first test is to rule out a faulty ECM!

If you do, then do test 1(b) and 1(c) and report the results!

But be sure that your multi-meter leads are connected to the appropriate pins at the ECM so as not to read false results!

I have a multimeter and know how to use it. So just like it is written in the FSM I need to start with the ECM.
I can't easily access the ECM, but from the diagram in the FSM and couple of Toyota videos it is located just under the pigeon hole in the passenger side inside the car.

I was thinking it's better to start from the easiest which are fuses and relays. Because if one has a blown fuse or bad relay either dedicated to the entire ECM or different terminals in the ECM, then the ECM will not work anyway.

By test 1(b) and 1(c) are you referring to the tests instructions on m_05_0057 for P0161/P0141 DTC's.
The question is why do I need to go as far as the ECM to test for voltage 9-14v when I can just test for the voltage at the wire harness, I presume the wire harness connector that couples with the sensor connector is coming from the ECM.

olaboy1:


Good I am paying attention in this tutorials.
It's very nice the car can enter fail safe mode to avoid further destruction. I hope it was able to keep my CAT from failing and maybe that's why I haven't got any CAT threshold DTC.
The content files in my FSM are not opening so it's very hard to get to the right info I need in it.
I will need info from the FSM on sensor oem part number, table of fuses and relays and what they control should I need to check all the fuses and relays controlling the sensors.

P0161 - https://www.dropbox.com/s/o97a1mizexac8uf/m_05_0057.pdf?dl=0
P1135/1155 - https://www.dropbox.com/s/hqfi3h17ggvhogy/m_05_0098.pdf?dl=0

olaboy1:
My findings so far. The FSM directive for the terminals is too dodgy for a beginner, as I don't understand if I am troubleshooting from the wire harness connector to the sensor or I need to go into ECM/ECU. I need you to break it down better for me. I can't say if I have done the electrical troubleshooting for all areas correctly but so far my findings below.

Bank 1 sensor 1 A/F sensor is the wrong sensor for that location, the one with DTC P1135. The resistance is 12.8ohms, the Toyota FSM wouldn't say what's the right ohms, but Bank 2 sensor 1 came out as 1.2ohms and that seem to be the right ohms reading for upstream oxygen sensors. So I guess a downstream sensor was used to replace an upstream sensor base on the ohms reading below. Resistance checks for the oxygen sensors were very straight forward, where I have difficulties trying to follow the FSM are continuity, short, voltage and wire harness resistance tests.

Resistance for sensors
Bank 1 sensor 1: 12.8ohms
Bank 2 sensor 1: 1.2ohms
Bank 1 sensor 2: 14.4ohms
Bank 2 sensor 2: 13.8ohms

Resistance for wire harness
Waiting for further directives.

Continuity
For continuity test I grounded the negative lead of my digital multimeter to a good ground, and used the positive lead to touch all the four pins in ONE sensor with ignition off and no beep. I repeated same process for all the 4 sensors no beep, went further to do same for all the 4 wire harness connector pins (16pins), and 3 wire harnesses came back with no beep except for the wire harness of bank 2 sensor 1 (P1155) that beeped. So tell me if I have done the continuity tests wrongly.
Bank 1 sensor 1: no beep
Bank 2 sensor 1: no beep
Bank 1 sensor 2: no beep
Bank 2 sensor 2: no beep
Bank 1 sensor 1 wire harness: no beep
Bank 2 sensor 1 wire harnesss: BEEP
Bank 1 sensor 2 wire harness: no beep
Bank 2 sensor 2 wire harness: no beep

Voltage tests
Also need more clarification to know if I have done the voltage tests correctly. With the ignition key set to ON without starting the car, I put my negative and positive DMM pins on 1 and 2 upper pins in the wire harness, I did not measure voltage for the sensors because they function at at around 600 degrees Fahrenheit.
Bank 1 sensor 1: not measured
Bank 2 sensor 1: not measured
Bank 1 sensor 2: not measured
Bank 2 sensor 2: not measured
Bank 1 sensor 1 wire harness: 11.9v
Bank 2 sensor 1 wire harness: 0v
Bank 1 sensor 2 wire harness: 0v
Bank 2 sensor 2 wire harness: 11.9v

Short
I haven't measured for short, I need more guidance as I don't quite understand the FSM.
NOTE: the two fans came on once I put the AC on and the AC works very fine and chilly.
I am attaching the dashboard pix with no temperature screen meter, my mechanic said this car uses dashboard light to show if the car is overheating.

Seen all the above

BUT
We have to establish if you followed the tests in the order that they ought to be done.

We would rather start with the oxygen sensor that is concerned with fuel air metering by the engine than the one that measures catalytic converter efficiency.

Subsequently, this post will be dissected and responded to, for now, we will just pass!

AutoElectNG:


P0161 - https://www.dropbox.com/s/o97a1mizexac8uf/m_05_0057.pdf?dl=0
P1135/1155 - https://www.dropbox.com/s/hqfi3h17ggvhogy/m_05_0098.pdf?dl=0

I don't have problem opening all the files under repair manual, data sheet etc, I've opened all the PDF files you instructed me to open on my ipad iBook. How do you locate the files for fixing a problem with ease without having to go through all the thousands of PDF files.

AutoElectNG:


Seen all the above

BUT
We have to establish if you followed the tests in the order that they ought to be done.

We would rather start with the oxygen sensor that is concerned with fuel air metering by the engine than the one that measures catalytic converter efficiency.

Subsequently, this post will be dissected and responded to, for now, we will just pass!

Remember we said all 4 sensors are priority 1 because FSM wrote that address all DTC's that are not fuel trim and misfire DTC's. Since am in the engine bay already I just thought I should take all the required readings at once.

If you insist we address the upstream A/F sensors first then I have no problem with that

Talking about starting from fuses and relays first, I am looking at the instruction book from the car and I see the table of the fuse box and on number 12: OBD 7.5 A: self diagnosis system.
Remember the report said no self test carried out.
So in this case wouldn't it be more logical to start from the 7.5A fuse than to go start checking the OBD2 interface.
What do you think

Sorry it's in Swedish, but I can translate.

olaboy1:


I have a multimeter and know how to use it. So just like it is written in the FSM I need to start with the ECM.
I can't easily access the ECM, but from the diagram in the FSM and couple of Toyota videos it is located just under the pigeon hole in the passenger side inside the car.

I was thinking it's better to start from the easiest which are fuses and relays. Because if one has a blown fuse or bad relay either dedicated to the entire ECM or different terminals in the ECM, then the ECM will not work anyway.

By test 1(b) and 1(c) are you referring to the tests instructions on m_05_0057 for P0161/P0141 DTC's.
The question is why do I need to go as far as the ECM to test for voltage 9-14v when I can just test for the voltage at the wire harness, I presume the wire harness connector that couples with the sensor connector is coming from the ECM.

Watch this video:

https://www.youtube.com/watch?v=nZVeOgusxqk

Your car is like a house

A house has different rooms

Power from the service provider is equivalent to your battery

The house's electrical box (panel) is roughly equivalent to your ECM

Individual circuits are connected to various bars in the circuit breaker the same way individual circuits (oxygen sensor, power steering, wipers, radio) are connected to various ECM pins so a fault in one circuit need not bring down all the circuits. In the same way, if a circuit is faulty, we have to run checks on the wires particular to that circuit and not anywhere else.

circuit breakers are like fuses

The problem has been narrowed down to the wiring between the ECM and the oxygen sensor

The type of problem has been narrowed down to an open or short in the heater circuit of the oxygen sensor or a faulty ECM, the specific wires that make up the heater circuit have been identified, a test to assess their integrity has been designed, and you want to test wires elsewhere that form part of an entirely different circuit?

Hope you also know that the ECM uses a PWM signal to control the oxygen sensors

How about a refresher course on Electricity Fundamentals 101, because this is not an electronic problem, but an electrical problem we are dealing with electric signals from the oxygen sensor are not getting to the ECM and electrical signals from the ECM are not getting to the oxygen sensor

olaboy1:


Good I am paying attention in this tutorials.
It's very nice the car can enter fail safe mode to avoid further destruction. I hope it was able to keep my CAT from failing and maybe that's why I haven't got any CAT threshold DTC.
The content files in my FSM are not opening so it's very hard to get to the right info I need in it.
I will need info from the FSM on sensor oem part number, table of fuses and relays and what they control should I need to check all the fuses and relays controlling the sensors.

Thanks to an intelligent ECM and OBD II's ability to compare several sensor inputs and decide on a regime of control that preserves vehicle sanity for want of a better word

olaboy1:
Talking about starting from fuses and relays first, I am looking at the instruction book from the car and I see the table of the fuse box and on number 12: OBD 7.5 A: self diagnosis system.
Remember the report said no self test carried out.
So in this case wouldn't it be more logical to start from the 7.5A fuse than to go start checking the OBD2 interface.
What do you think

Valid point raised.

Checked my subscription to another OEM's factory data, ECM test is the last, unlike Toyota.

But OEMs are different and implement vehicle control logic differently.

If that is what you prefer, then let us using the FSM, start from the oxygen sensor and work our way to the ECM.

At the ECM, we are not checking the OBD II interface, we would be checking the heater circuit's wiring at the ECM to confirm or deny that voltage signals at the ECM meant for the oxygen sensor are within specifications

That was an interesting read and comparative analysis. My questions are
1. Do we have fuses/relay in the fuse box controlling different circuit/pins in the ECM. Meaning that from battery ---->fuse box----->ECM
2. The FSM wants us to check for voltage ONLY from the ECM 1(b) and 1(c), does that mean ECM supplies only voltage to the oxygen sensor?
3. Why do we need to measure voltage inside the ECM and not just measure the voltage from the wire harness coming from the ECM as the ECM is hard to get to
4. Could you please explain further what you mean by the ECM using PWM signal to control the oxygen sensor

AutoElectNG:


Valid point raised.

Checked my subscription to another OEM's factory data, ECM test is the last, unlike Toyota.

But OEMs are different and implement vehicle control logic differently.

If that is what you prefer, then let us using the FSM, start from the oxygen sensor and work our way to the ECM.

At the ECM, we are not checking the OBD II interface, we would be checking the heater circuit's wiring at the ECM to confirm or deny that voltage signals at the ECM meant for the oxygen sensor are within specifications

Yes sure we are not looking at OBD at the ECM, that was just an illustration I made.
I have read this car's FSM and on many occasions the repair ends with ECM even the CMP sensor repair flow chart ends with ECM.
So if my voltage test procedure of the wire harness coming from the ECM was anything to go by, I am getting 11.9v on two wire harnesses and 0v on the other 2, are there fuses or relays controlling voltage sent to the ECM from the battery.

Starting from oxygen sensors, I have done the resistance tests correctly, how do I check for continuity properly using the FSM stated terminals to check.

olaboy1:
That was an interesting read and comparative analysis. My questions are
1. Do we have fuses/relay in the fuse box controlling different circuit/pins in the ECM. Meaning that from battery ---->fuse box----->ECM
2. The FSM wants us to check for voltage ONLY from the ECM 1(b) and 1(c), does that mean ECM supplies only voltage to the oxygen sensor?
3. Why do we need to measure voltage inside the ECM and not just measure the voltage from the wire harness coming from the ECM as the ECM is hard to get to
4. Could you please explain further what you mean by the ECM using PWM signal to control the oxygen sensor

1. Do we have fuses/relay in the fuse box controlling different circuit/pins in the ECM.

Yes, remove a fuse or relay, and the circuit drops dead, no current flows

2. The FSM wants us to check for voltage ONLY from the ECM 1(b) and 1(c), does that mean ECM supplies only voltage to the oxygen sensor?


The FSM wants you have an idea:

what kind of voltage is the ECM sending to the heater circuit of the oxygen sensor?

What does the oxygen sensor see?

Is it within specifications or not?

There is a relationship between voltage and current, once the voltage is correct, the amperage will be.

The ECM controls/monitors the oxygen sensors voltage and current.

The FSM wants you to confirm that the ECM is able to control the oxygen sensors, and says that once you have verified that control, by the voltage being within specifications

THEN

verify that oxygen sensor itself is not bad, if it is good then the resistance should be within the specifications provided, if it is not, then it should be replaced

THEN

verify the integrity of the wiring between the ECM and the oxygen sensor connector, if it fails the integrity test, then repair or replace the wiring
this is a resistance aka continuity test not a voltage test!

THEN

verify the integrity of the wiring between the oxygen sensor connector and the EFI relay
this is a resistance aka continuity test not a voltage test!

3. Why do we need to measure voltage inside the ECM and not just measure the voltage from the wire harness coming from the ECM as the ECM is hard to get to?


We think you meant measure the voltage at the ECM pins, because ignition is on, ECM wiring harness is not disconnected, you are probing the ECM from outside it not inside it LOL.

Truth is you cannot fix this without learning how to access the ECM or being willing to access the ECM.

You have to learn to be comfortable with the idea of disrobing your vehicle if you want to fix electrical issues


4. Could you please explain further what you mean by the ECM using PWM signal to control the oxygen sensor

More accurately, ECM uses PWM to control the wideband A/F oxygen sensor

Basic four-wire O2 sensors are still used as catalyst monitors and labeled sensor S2 on bank 1 or bank 2 (B1S2 or B2S2). The heater brings the sensor up to operating temperature quickly so it can begin working as soon as possible. The PCM monitors the heater circuits continuously, checking resistance for an open circuit or short to ground.

If a problem is detected, the PCM will set a code and turn on the malfunction indicator light (MIL), but the sensor can still produce a signal if the exhaust gas keeps it hot enough.

AFR sensors might also produce a signal without the heater, but that signal would be completely useless because it’s not voltage... it’s a measure of the current sent to the oxygen pump. Temperature affects resistance and resistance affects current flow, so the sensor’s flat zirconia strip must be held at a constant temperature to generate an accurate signal. The sensor is heated to about 1,200 degrees F (650 degrees C), double the temperature of a basic heated oxygen sensor.

Sensor heaters can draw a lot of current, so battery voltage is usually supplied directly to the heaters through a relay and a fuse. The heaters’ ground circuit is controlled by the PCM. A basic four-wire sensor heater is usually turned on all the time, but the AFR heater’s ground circuit is pulse width-modulated to keep the temperature constant regardless of exhaust gas temperature.

There is no temperature sensor in these heaters, so how does the PCM keep the AFR sensor at a constant temperature? Remember that temperature affects resistance, so the PCM can calculate the sensor’s temperature by monitoring the resistance in the heater circuit. General Motors (GM) calls this Resistance Calculated Oxygen Sensor Heater Temperature (RCOHT). The same principal is used to measure coolant temperature, but in this application the measurements must be extremely fast and infinitely more precise.

The heater circuit has a calibration resistor built into the wiring harness or sensor connector.

When the sensor is first installed and connected, the PCM is commanded to read the resistance in the (cold) heater circuit to know the calibration of that resistor. It will then use that resistance value to calculate the sensor’s actual temperature under all conditions.

Even with a calibration resistor, the heater’s resistance varies by a few hundredths of an ohm from one AFR sensor to another. That’s why the PCM and the AFR sensor heater must be calibrated to each other. That’s also why there is no heater resistance specification, so measuring heater resistance is not a good way to confirm a good/bad oxygen sensor heater. In addition, that’s the other reason we’re told not to repair an AFR sensor’s wiring harness; the resistance might change.

When replacing an air/fuel ratio sensor, you’ll need a scan tool capable of commanding the PCM to relearn the sensor heater’s resistance. On some models, simply clearing the trouble codes and turning off the MIL will do the job. Some scan tools won’t enter the clear-code mode if no codes exist. In that case, just turn on the ignition and disconnect any convenient sensor to create a code. On some models the relearn must be done with the sensor at ambient temperature. On many GM models it can be done with the sensor hot, and the PCM will relearn the real value at the next cold-start.

Source: http://www.autoserviceprofessional.com/article/95805/oxygen-sensor-heaters-how-do-you-know-if-that-heater-fault-code-is-real

To break it down clearly.
1. ECM check is for voltage
2. Oxygen sensor check is for resistance, continuity, short and voltage (The voltage test is well done when the sensor is heated to 600-1200 degrees Fahrenheit and best tool for this is an OBD2 scanner as that would also show us the frequency movement we should expect in a FSM specified voltage range)
3. Wire harness check is for resistance, continuity, short and voltage. (The voltage test will be when the wire harness is connected to the ECM and ignition switch ON and a DMM comes in handy to do just that job)
4. E.F.I relay is to check continuity between its relay block and the heater terminal of the oxygen sensor

Can you direct me to the fuses/relays positions in the fuse box controlling all the 4 oxygen sensors voltage circuit in the ECM. If I am correct each sensor has it's own connector pins on the ECM and of course should have dedicated fuse/relay e.g ECM E10 and E9 connectors for the downstream sensors giving DTC's P0161/P0141.

I want to start from fuses and relays because that's where I first look as a novice anytime I have a problem with my car.

My FSM is asking me to check for resistance only in the oxygen sensor. Please how do I check for continuity and short, I don't need to check for voltage anyway if I don't have continuity or if I have a short, I will just go ahead and change the sensor.

The PDF file m_05_0057 for the downstream sensors (P0161/P0141) is very clear, but the PDF file m_05_0098 for the upstream sensors(P1135/P1155) did not explain the rapair procedure like it did for the former. Where do I look to get same repair info contained in m_05_0057.

I appreciate your time and effort.