Trouble Code Conditions

SPECIAL TOOLS
Volvo scan tool No. 998 8686 or equivalent

CONDITION
Solenoid S1 operates in tandem with solenoid S2 to control gear-shifting. Solenoid S1 operates when it receives a battery voltage from the transmission control module (TCM) and is activated in 2nd and 3rd gears. Diagnostic trouble code (DTC) AT-121 is posted if the transmission control module (TCM) 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
The transmission control module (TCM) limp-home program has been initiated.
Possible source
- 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 (TCM) 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 (DTC) when the transmission sends a malfunction indicator lamp (MIL) request.
- Erase this diagnostic trouble code (DTC) in the Motronic engine control module (ECM) when the transmission fault has been repaired.

TESTING PROCEDURE
- Start fault-tracing at Short Circuit To Ground. Short-Circuit To Ground