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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Chevy K Silverado - 4WD 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P1571

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.

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.

  1. This step determines if the circuit is shorted to ground.

    2.

  2. This step determines if the circuit is shorted to battery voltage.

    3.

  3. This step determines if the circuit is open.

DTC P1571 (8.1L)

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 - Automatic Transmission?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. 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.

  3. Record the DTC Freeze Frame and Failure Records.
  4. 4. Clear the DTC.
  5. 5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and Failure records.

Is DTC P1571 currently active?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn the ignition OFF.
  2. Disconnect the PCM connector C1 (BLUE).
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the requested torque signal circuit of the PCM harness connector C1 terminal 13 with a test lamp connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 5

4

  1. Turn OFF the engine.
  2. Disconnect the TCM connector C1 (GRAY).
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the requested torque signal circuit of the PCM harness connector C1 terminal 13 with a test lamp connected to battery voltage. Refer to Testing for Short to Ground in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 9

5

  1. Probe the requested torque signal circuit of the PCM harness connector C1 terminal 13 with a DMM that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
  2. Using a DMM, observe the AC frequency on the DMM. Refer to Measuring Frequency in Wiring Systems.

Is the frequency greater than the specified value?

100 Hz

Go to Step 6

Go to Step 7

6
  1. Disconnect the TCM connector C1 (GRAY).
  2. Probe the requested torque signal circuit of the PCM harness connector C1 terminal 13 with a test lamp connected to a good ground. Refer to Testing for a Short to Voltage in Wiring Systems.

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 Transmission Control Module Replacement .

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L.

Did you complete the replacement?

--

Go to Step 14

--

14

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and Failure records.
  6. Select Specific DTC.
  7. 7. Enter DTC P1571.

Has the test run and passed?

--

System OK

Go to Step 1