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Thank you so much my brother. We took the car for recalibration and Tcm reset and the tranny is very fine now. I'm just seeing your detailed response. God bless you and thank you for the good job that you're doing here.

RyanAutomotive:
Good morning sir.

Thank you for the detailed explanation. Transmission issues like this require a very careful and structured diagnostic approach, especially on modern Lexus vehicles. Let’s examine the situation properly before any expensive components like the TCM are replaced.

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🔎 Professional Diagnostic Insight

Vehicle: Lexus RX350 2013
Initial Fault Code: P0715 – Input/Turbine Speed Sensor “A” Circuit

This sensor monitors the speed of the transmission input shaft and sends that information to the Transmission Control Module (TCM) so the system can determine:

• Correct gear engagement
• Shift timing
• Torque converter operation
• Hydraulic pressure control

When the sensor fails or sends incorrect data, the transmission may:

• Get stuck in a specific gear
• Shift erratically
• Enter a protective fail-safe mode

Replacing the sensor was the correct first step, and the fact that the vehicle now selects all six gears again indicates that the original fault was likely addressed.

However, the remaining slip between gear 1 and 2 suggests there may still be an underlying issue.

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1️⃣ Residual Adaptation / Calibration Issue

After replacing certain transmission components or sensors, the transmission computer may still retain old adaptive learning values.

These stored values affect:

• Shift pressure
• Clutch engagement timing
• Gear transition behavior

If they are not properly reset using a professional diagnostic scanner, the transmission may continue to behave incorrectly.

A proper TCM adaptive reset and relearn procedure is sometimes required.

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2️⃣ Valve Body or Solenoid Performance

If the slipping occurs only between gear 1 and 2, this may indicate a hydraulic control issue within the valve body assembly.

Possible causes include:

• Weak or sticking shift solenoid
• Hydraulic pressure imbalance
• Internal valve body wear

These issues may not always trigger fault codes, especially if the system still manages to complete the shift.

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3️⃣ Transmission Fluid Condition

Transmission slipping can also occur when:

• Fluid is degraded or burnt
• Incorrect fluid type is used
• Fluid level is not correctly set at operating temperature

The RX350 transmission is very sensitive to fluid condition, and improper servicing can affect gear engagement.

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4️⃣ TCM Replacement Consideration

Replacing the Transmission Control Module (TCM) should always be the last step, not the first.

In practice, TCM failure on this model is much less common than:

• Valve body issues
• Solenoid performance problems
• Fluid pressure imbalance
• Incomplete adaptation reset

Therefore, replacing the TCM without confirming these areas can lead to unnecessary expense without solving the problem.

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⚠️ Important Observation

The absence of fault codes does not always mean the transmission is perfectly healthy.

Many hydraulic or mechanical issues occur without immediately triggering diagnostic codes, especially when the system still manages to shift through the gears.

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📌 What Should Be Checked Next

Before considering TCM replacement, the following should be done:

1️⃣ Perform a complete transmission live-data analysis
2️⃣ Verify transmission fluid condition and level
3️⃣ Perform a proper TCM adaptive reset and relearn procedure
4️⃣ Test shift solenoid response and hydraulic pressure behavior
5️⃣ Inspect the valve body assembly if slipping persists

This approach ensures the exact cause is identified rather than replacing parts based on assumption.

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🎯 Professional Take

From experience with Lexus RX transmissions, slipping between 1st and 2nd gear after sensor replacement is more commonly related to adaptation or valve body control, not the TCM itself.

Proper diagnostic testing will determine whether the issue is electronic calibration or hydraulic control.

Addressing it early helps prevent further internal clutch wear.

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🏢 Ryan Automotive Limited Recommendation

At this stage, the vehicle should undergo structured transmission diagnostics, including live data analysis and adaptive system reset, before any major component replacement.

This ensures the exact source of the slipping is identified and resolved correctly.

If you are able to bring the vehicle down, Ryan Automotive Limited performs professional transmission diagnostics and fault isolation to accurately determine whether the issue lies with calibration, solenoids, or internal hydraulic control.

This avoids unnecessary replacement of expensive components like the TCM.

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Precision • Transparency • Excellence

Ryan Automotive Limited
Transmission Diagnostics | Fault Code Analysis | Professional Repair Approach 🚗🔧

I replaced the fuses because many of them had wires wrapped around them. So, I said rather than manage, let's replace and we bought four packs

Guys, I need help. My RX350 2013 does no longer detect my key fob. It started last night. I also observed that my driver's seat exit system stopped working (steering doesn't go in or out and seat doesn't slide front or back when I start or switch off the car. This also started yesterday after I replaced all the fuses in the car to new ones. Please what may be wrong with it? Your advise will be appreciated 🙏. Thank you.

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Guys, please I need your advice. The transmission of my Rx350 2013 is slipping. It stalled at the second gear. I took it for a scan and it threw up fault code P0715 (input Turbine/speed control sensor A). A gear master has changed this sensor and the car now selects all 6 gears. But I discovered that it still slips between gear 1 and 2. It easily selects other gears. The gear master is advising me to change the TCM that it might be the culprit. We have scanned and rescanned and there's no more fault codes from the gear. I read on Google that we need to reset the TCM, yet, the gear master says he has calibrated the car. I'm a little at lost on what to do next. Kindly advise.

Guys, please I need your advice. The transmission of my Rx350 2013 is slipping. I took it for a scan and it threw up fault code P0715 (input Turbine/speed control sensor A). I've taken it to that gear master and he's going to open the gearbox tomorrow. We've checked the wire harness for any possible damage and even changed the PCM but it keeps throwing the same fault code. In fact, we changed the brain box of the car just to be sure that nothing is wrong with the ECU. I just did an oil change on the transmission. The gear master seems certain that it's the sensor, hence, he will be opening it tomorrow. Do I really need to be worried? Is it a minor fix? Kindly advice.