Trouble Code Conditions

Special Tools
- 981 3190
- 998 8686

Trouble Code Conditions
- System pressure solenoid STH controls system pressure in the transmission. The solenoid is controlled by an amplifier in the transmission control module (TCM) output.
- The transmission control module uses the amplifier to control the current to the solenoid. A low amperage provides a high system pressure and a high amperage (approx. 1A) provides a low system pressure. This amperage is primarily affected by throttle position. Diagnostic trouble code (DTC) AT-123 is stored if the transmission control module registers a short-circuit to supply voltage in the solenoid STH circuit causing a high amperage. Solenoid STH cannot control system pressure.

Substitute value(s)
- The transmission control module limp-home program has been initiated.

Possible source(s)
- Short-circuit to supply voltage in the signal cable.
- Defective solenoid STH.

Fault symptom(s)
- The combined instrument panel warning lamp flashes.
- Deterioration in performance because the transmission control module prevents activation of the solenoids, this stops gear-shifting. The transmission only operates in 3rd gear in positions 3 and L, 4th gear in position D and reverse in position R. Shifting can only be carried out manually between 3rd, 4th, and reverse gears.
- No lock-up function.

CAUTION: There is a danger that system pressure may be too low, which will result in wear.

NOTE: The Motronic 4.4 engine control module (ECM) posts a diagnostic trouble code when the transmission sends a malfunction indicator lamp (MIL) request. Erase this diagnostic trouble code in the Motronic engine control module when the transmission fault has been repaired.

- Start fault-tracing. Short-Circuit To Supply Voltage