Trouble Code Conditions

SPECIAL TOOLS
Test box tool No. 981 3190, or equivalent
Volvo scan tool No. 998 8686, or equivalent

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 (DTCs) AT-321, AT-322, AT323 or AT-324 are posted if the TCM registers a deviation of more than 10% in these ratios, depending on the gear. Oil temperature must be above +20°C and throttle position above 3%.

SUBSTITUTE VALUE
The TCM limp-home program has been initiated.

POSSIBLE SOURCE
- Interference with or faulty transmission speed sensor signal
- Interference with faulty Vehicle Speed Sensor (VSS) signal
- Contact resistance in the Solenoid S1 and S2 circuits.
- Gear-shift position sensor incorrectly adjusted
- Transmission oil level too low.
- Mechanical fault in the transmission. Worn components in the transmission causing slippage or reduced system pressure.
- Defective power ground
- Transmission speed sensor signal cable (-) short circuited to ground.

FAULT SYMPTOM(S)
- The combined instrument panel warning lamp flashes.
- Mechanical malfunction. Faults are usually indicated by noise or other obvious function problems.
- Deterioration in performance because the 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 DTC when the transmission sends a Malfunction Indicator Lamp (MIL) request
- Erase this DTC in the Motronic ECM when the transmission fault has been repaired.

TESTING PROCEDURE
- Start fault-tracing at incorrect gear ratio. Testing