4T65EV Transmission

Diagnostic trouble code (DTC) information

Condition




The transmission control module (TCM) calculates the ratio between the transmission input speed and the vehicle speed. There is a specific ratio for each gear. Diagnostic trouble code (DTC) TCM-0027 is stored if the control module registers that the ratio deviates by more than 10% when oil temperature is above +20°C and throttle opening exceeds 3%.

Substitute value
- The control module "Limp Home" program initiated.

Possible source
- Contact resistance in the Solenoid S1 and S2 circuits.
- Interference with or faulty transmission speed sensor signal.
- Interference with or faulty speed signal from transmission speed sensor.
- Gear-shift position sensor incorrectly adjusted.
- Transmission oil level too low.
- Mechanical fault in the transmission. Worn components in the transmission causing slippage or too low line pressure.
- Defective power ground.
- Short-circuited to ground in transmission speed sensor signal cable.

Fault symptom[s]
- General orange warning lamp lit.
- Malfunction indicator lamp (MIL) lit.
- No lock-up function.
- No shifting.
- Harsh gear shifting.

Hint: Harsh shifting - due to disabled line pressure solenoid STH control. This results in constant maximum line pressure.
No shifting - because the transmission control module (TCM) prevents activation of the solenoids. This stops gear-shifting.