Trouble Code Conditions

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Trouble Code Conditions
- Shift solenoids S2 and S1 operate in tandem to control gear-shifting. Solenoid S1 operates when battery voltage is applied from the transmission control module (TCM) and is activated on reverse, 1st and 2nd gears. Diagnostic trouble code (DTC) AT-121 is stored it the transmission control module registers a short-circuit to ground in the solenoid S1 circuit when the solenoid should be activated. Solenoid S1 cannot then be activated.

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

Possible source(s)
- Short-circuit to ground in signal cable.
- Defective solenoid.

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 operates only 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 gear.
- No system pressure solenoid STH control resulting in constant maximum system pressure leading to harsher shifting and gear meshing.
- No lock-up function.

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 Ground