Allison Automatic Transmission

ALLISON AUTOMATIC TRANSMISSION

DTC P0712

DTC P0712 Step 1 - 7:

DTC P0712 Step 8 - 12:

Circuit Description for Allison Automatic Transmission
The Transmission Fluid Temperature (TFT) sensor is a part of the Pressure Switch Manifold (PSM) assembly and is located in the transmission oil pan. The TFT sensor is a thermistor, which changes value based on the temperature of the transmission fluid. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases, as the temperature decreases, the resistance increases. The Transmission Control Module (TCM) supplies a 5 V reference signal to the TFT sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the TCM detects high signal voltage. As the fluid temperature warms to normal operating temperature, the resistance becomes less and the signal voltage decreases. The TCM uses this information to control shift quality and torque converter clutch apply. DTC P0712 is a type B DTC.

Conditions for Running the DTC
^ No DTC, P0711, P0712, P0713.
^ The components are powered and ignition voltage is greater than 9 V and less than 18 V.
^ Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
^ Engine has been running for 20 seconds with coolant temperature above 20°C (SELF).

Conditions for Setting the DTC
DTC P0712 sets when the TCM detects less than 150°C (302°F) for 2 seconds.

Action Taken When the DTC Sets
^ The TCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The TCM uses a TFT default value.
^ The TCM freezes shift adapts.
^ The TCM stores this information as Failure Records.
^ The TCM stores DTC P0218 in TCM History
^ TCM inhibits TCC engagement.

Conditions for Clearing the MIL/DTC
A scan tool can clear the code from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
^ Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation.
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ You may have to drive the vehicle in order to experience a fault.
^ A short to ground on circuit (CKT 1227) will allow a code P0712 to set.

Test Description
The numbers refer to the step numbers on the diagnostic table.
4. This step tests 5 V reference voltage.
5. This step tests the sensor and internal wiring harness.
6. This step tests the wiring harness for a short to ground.
8. This step tests the resistance of the TFT sensor.