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Transmission Problems-code P0780: Siena and other Auto Gurus - Autos - Nairaland

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Transmission Problems-code P0780: Siena and other Auto Gurus by Costee: 10:17am On May 19, 2011
The A/T of my 2006 Maxima has been misbehaving since the past month. Once it gets hot (especially in traffic), it seems to have conflicting signals in the change of gears. On such occasions the rpm dial flutters, nudging the higher numbers and back. Again, when the reverse is engaged there is a slight delay and then a lurch. The tranny finally pulled the code P0780 two days ago. I checked it and this is what it says: Shift Control System Fault and the causes are

(1)- Low transmission fluid level
(2)- Dirty transmission fluid
(3)- Faulty shifting solenoid valve
(4)- Shifting solenoid valve harness or connectors
(5)- Shifting solenoid valve circuit is open or shorted

I can easily identify 1 & 2. I have topped off the tranny with Matic K ATF which is the specification in the manufacturer’s manual. As for #2, I wouldn’t say the fluid is black dirty. Anyway, I intend to drain it in the coming week (Matic K is not locally available) to be on the safe side. There has been a slight improvement since I added the fluid, though the code is still showing.
Now for  #3-5. #5 seems to be off as the manual itself says “this is not caused by electrical malfunction (circuits open or shorted) but by mechanical malfunction such as control valve sticking, improper solenoid valve operation, etc.
That leaves me with #3 and 4. I don’t understand what they mean, and I want informed knowledge before I take the car to the auto workshop. Would they be referring to the tranny mounts?
Re: Transmission Problems-code P0780: Siena and other Auto Gurus by Costee: 9:25pm On May 19, 2011
Here's a more technical info, and perhaps more precise.

DTC P0780 SHIFT
Description
1. This malfunction will not be detected while the A/T CHECK indicator lamp is indicating another self-diagnosis malfunction.
2. This malfunction is detected when the A/T does not shift as instructed by the TCM. This is not caused by electrical malfunction (circuits open or shorted) but by mechanical malfunction such as control valve sticking, improper solenoid valve operation, etc.

On Board Diagnosis Logic
1. This is an OBD-II self-diagnostic item.
2. Diagnostic trouble code “SHIFT” with CONSULT-II or P0780 without CONSULT-II is detected under the
following conditions.
– When no rotation change occurs between input (turbine revolution sensor) and output (revolution sensor) and shifting time is long.
– When shifting ends immediately.
– When engine revs up unusually during shifting.

Possible Cause
1.Shift solenoid valve D (Off error.)
2. Shift solenoid valve E (Off error.)
3. Pressure control solenoid valve A (On/Off error.)
4. Pressure control solenoid valve B (On/Off error.)
5. Pressure control solenoid valve C (On/Off error.)
6. Hydraulic control circuit

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