P1571

ALLISON AUTOMATIC TRANSMISSION

DTC P1571
Circuit Description for Allison Automatic Transmission
The transmission control module (TCM) sends a signal to the powertrain control module (PCM) on the requested torque signal circuit. This signal commands the PCM to limit engine torque under certain extreme driving conditions.

DTC P1571 is a type B DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1571 Transmission Torque Request Circuit

Conditions for Running the DTC
The engine is running.

Conditions for Setting the DTC
The PCM detects one of the following conditions on the requested torque signal circuit:
^ An open
^ A short to ground
^ A short to battery voltage

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.
^ DTC P1571 will be stored in TCM history.

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

Diagnostic Aids
^ Inspect the wiring for poor electrical connections at the PCM and TCM. Inspect 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 condition.

Test Description








The numbers below refer to the step numbers on the diagnostic table.
4. This step determines if the circuit is shorted to ground.
5. This step determines if the circuit is shorted to battery voltage.
6. This step determines if the circuit is open.