Circuit Description
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.
-
This step determines if the circuit is shorted to ground.
-
This step determines if the circuit is shorted to battery voltage.
-
This step determines if the circuit is open.
Step | Action | Value | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics | ||||
1 |
Important: This DTC will set if the TCM has been replaced and not programmed. Ensure that the TCM has been programmed before proceeding with this diagnostic. Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Is DTC P1571 currently active? | -- | Go to Step 3 | Go to Diagnostic Aids |
3 |
Does the test lamp illuminate? | -- | Go to Step 4 | Go to Step 5 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 9 | |
Is the frequency greater than the specified value? | 100 Hz | Go to Step 6 | Go to Step 7 | |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 12 | |
7 | Test the requested torque signal circuit for an open. Refer to Testing for Continuity in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 8 |
8 | Test for an intermittent and a poor connection at the TCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 12 |
9 | Test for an intermittent and a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 14 | Go to Step 13 |
10 | Repair the short to voltage in the requested torque signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
11 | Repair the short to ground in the requested torque signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
12 |
Important: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM. Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | -- |
14 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK | Go to Step 1 |
