Allison 1000 & 2000 Gen 4 Fault Codes: P0711 Transmission Fluid Temperature Sensor Circuit Performance

Allison 1000 & 2000 Gen 4 Fault Codes: P0711 Transmission Fluid Temperature Sensor Circuit Performance

CIRCUIT DESCRIPTION:
The Transmission Fluid Temperature (TFT) sensor is part of the Pressure Switch Manifold (PSM) which is located in the transmission oil pan. The TFT sensor is a thermistor that changes its resistance value based on the temperature of the transmission fluid. The Transmission Control Module (TCM) supplies a 5V reference signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission is cold, the sensor resistance is high and the TCM detects high signal voltage. As the transmission fluid temperature warms to a normal operating temperature, the resistance becomes less and the signal voltage decreases. The TCM uses this information to control shift quality and to determine torque converter clutch applies.

If the TCM detects the TFT sensor resistance has no change, an unrealistic change in a short amount of time, or multiple changes within seconds, DTC P0711 sets.

CONDITIONS FOR RUNNING THE DTC:
1. No DTC P0721, P0722, P0717, P0716, P0713, or P0712.
2. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).
3. The engine speed is greater than 200 rpm for more than 5 seconds.
4. The engine speed is greater than 450 rpm for more than 2 seconds with output speed of 100 rpm or above. This would indicate that a range is selected.
5. A valid start-up temperature is detected.

CONDITIONS FOR SETTING THE DTC:
DTC P0711 sets when the TCM detects one of the following conditions:
1. The TCM detects a temperature change that is under a set limit when compared to samples of the minimum and maximum temperature values.
2. The TFT has an unrealistic temperature change of more than 10°C (50°F) for 10 occurrences.
3. The temperature from start up decreases 40°C (104°F) or more within duration of 6 or more seconds.

ACTION TAKEN WHEN THE DTC SETS:
1. The TCM does not illuminate the CHECK TRANS light.
2. The TCM stores DTC P0711 in TCM history.
3. The TCM uses calibration default for temperature values.

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
1. A Scan Tool may be used to clear the code from the TCM history.
2. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.
3. The TCM cancels the DTC default actions when the fault no longer exists and the ignition has been cycled.

DIAGNOSTIC AIDS:
1. The Scan Tool transmission fluid temperature (TFT) should rise steadily during warm-up cycles and then stabilize.
2. DTC P0218 may set after DTC P0711 has set. Follow the diagnostic information for DTC P0711 before proceeding to the diagnostic for DTC P0218.