Trouble Code Conditions

SPECIAL TOOLS
Volvo scan tool No. 998 8686, or equivalent

CONDITION
The oil temperature sensor sends a signal to the Transmission Control Module (TCM) which is used for functions such as temperature controlled lock-up and initiating high-temperature programs. The sensor has an NTC (negative temperature coefficient) resistor. The signal (resistance) sinks proportionate to the rise in the oil temperature. Diagnostic Trouble Code (DTC) AT-235 is posted if the TCM receives a signal from the oil temperature sensor corresponding to a temperature above approx. +140°C for approx. 5 seconds.

SUBSTITUTE VALUE
None.

POSSIBLE SOURCE
- Short-circuit to ground in signal cable.
- Defective oil temperature sensor.
- Mechanical malfunction in the transmission.
- The transmission has been exposed to extreme load and temperature.

FAULT SYMPTOM(S)
- The warning lamp flashes when the DTC is posted and stops flashing when the TCM receives a signal that oil temperature has fallen below +135°C.

CAUTION: If you suspect that the transmission oil temperature has exceeded +135°C it must be changed.

TESTING PROCEDURE
- Start fault-tracing at Too High. Signal Too High