P1571

Circuit Description

This diagnostic test checks for a traction control system Pulse Width Modulated signal failure to the PCM. The PCM sends 5 volts on the desired torque circuit (CKT 463) to the Electronic Brake and Traction Control Module (EBTCM). The EBTCM then rapidly switches this CKT to ground creating a PWM (frequency) signal to request a specific amount of torque reduction during a Traction Control Maneuver. If this PWM signal is not received by the PCM for 3 seconds, DTC P1571 is set.

Conditions for Running the DTC

^ DTC P1602 not set.
^ Traction control not failed.
^ Engine speed greater than 500 RPM for 20 seconds.

Conditions for Setting the DTC

PWM (frequency) signal not received on desired torque circuit for 3 seconds.

Action Taken When the DTC Sets

^ PCM disables first gear starts.
^ Transaxle shift adapts are maintained at current levels.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ No message will be displayed.

Conditions for Clearing the DTC

^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

This DTC may set along with several others if the key is held in the CRANK position while the engine is running. The starter lockout function of the PCM is enabled several seconds after the engine is running and will prevent the starter from engaging while the engine is running. This will cause a partial loss of power to some components and systems.

If no fault is present refer to the A Diagnostic System Check - ABS to aid in isolating an intermittent fault.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

3. The PCM supplies 5 volts on the Desired Torque circuit. A voltage outside of the range indicates a circuit or PCM fault.
4. When shorting the Desired Torque circuit to ground the scan tool will display low desired torque percent for only a few seconds regardless of how long the Desired Torque circuit is shorted to ground.
5. To determine if a short exists between the Desired Torque circuit and another 5 volt circuit (I.E. MAP reference, ECT signal, ect.) disconnect both PCM connectors and measure the resistance between the Desired Torque circuit and all other PCM terminals. Resistance between circuits should measure infinite (OL).
7. When checking for shorts to ground or shorts to other circuits, resistance of more than 10K ohms is usually acceptable although most readings should be infinite (OL).
When checking for circuit continuity (opens) resistance should be 5 ohms or less.