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 codes (DTC) TCM-0028, TCM-0029, TCM-002A or TCM-002B are stored (depending on the gear selected) if the control module, when the oil temperature is above +20°C and throttle opening exceeds 3%, registers that the ratio deviates by more than 10%.

Substitute value
- The control module "Limp Home" program has been 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 the transmission speed sensor.
- Short-circuit to ground in the engine speed (RPM) sensor signal cable (-).
- Incorrectly adjusted gear-shift position sensor.
- The transmission oil level is too low.
- Mechanical fault in the transmission. Worn components in the transmission causing slippage or too low line pressure.
- Defective power ground.

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

Hint: Harsh shifting -may be due to no 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. The transmission only operates in 3rd gear in positions 1 and 2, in 4th gear in positions D and 3, and in reverse gear in position R. Shifting can only be carried out manually between 3rd, 4th and reverse gears.