Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information

Condition




The transmission control module (TCM) and engine control module (ECM) communicate via a standardized serial interface. Both the control modules transmit and receive information. Diagnostic trouble codes (DTCs) AT-521, AT-522, AT-523, AT-524, AT-525, AT-526 or AT-527 are stored if the control module detects a disruption of communication or a communication failure.

Substitute value

Diagnostic Trouble Code (DTC) AT-526
- No substitute values.

Diagnostic Trouble Code (DTC) AT-521
- The control module "Limp Home" program has been initiated.

Diagnostic trouble codes (DTCs) AT-522, AT-523 and AT-527
- The transmission control module (TCM) "Emergency mode III"program has been initiated.

Diagnostic trouble codes (DTCs) AT-524 and AT-525
- The transmission control module (TCM) "Emergency mode I"program has been initiated.

Possible source
- Open-circuit in one or both signal cables.
- Short-circuit to ground, voltage or each other in one or both signal cables.
- Contact resistance in the terminals.
- Faulty transmission control module (TCM).
- Defective engine control module (ECM).

Fault symptom[s]

Diagnostic Trouble Code (DTC) AT-526
- No fault symptoms

Diagnostic Trouble Code (DTC) AT-521
- The warning lamp in the combined instrument panel flashes.
- No lock-up function.
- Deterioration in performance because the transmission control module (TCM) inhibits the activation of solenoids which prevents gear shifting. The transmission only works with 3rd gear in positions 3 and L, 4th gear in positions D and R.
- No line pressure solenoid STH control resulting in constant maximum line pressure. This leads to harsh shifting and gear engagement.

Diagnostic trouble codes (DTCs) AT-522, AT-523 and AT-527
- The warning lamp in the combined instrument panel flashes.
- No lock-up function.
- No adaptation of the gear slippage times at high altitude.
- No torque limiting request to engine control module (ECM) when shifting.
- No line pressure solenoid STH control resulting in constant maximum line pressure. This leads to harsh shifting and gear engagement.

Diagnostic trouble codes (DTCs) AT-524 and AT-525
- The warning lamp in the combined instrument panel flashes.
- No lock-up function.
- No adaptation of the gear slippage times at high altitude.