DTC P1571 Traction Control Torque Request Circuit
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PostPosted: Thu Nov 11, 2004 11:01 am    Post subject: DTC P1571 Traction Control Torque Request Circuit Reply with quote

DTC P1571 Traction Control Torque Request Circuit


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Circuit Description

The PCM supplies 5.0 volts on the Desired Torque circuit to the Electronic Brake and Traction Control Module (EBTCM). The EBTCM toggles this 5.0 volt signal to a ground in order to produce a duty cycle signal. The signal is proportional to the amount of engine output torque reduction requested by the EBTCM. The EBTCM supplies this signal when it detects a wheel slip. In order to reduce engine output torque, the PCM reduces the amount of spark advance and in some cases the PCM disables a number of fuel injectors. This diagnostic test checks for a Desired Torque signal failure. If the PCM does not receive the Desired torque signal this DTC sets.

Conditions for Setting the DTC
  • The traction control has not failed.
  • The engine speed is greater than 500 RPM for 20 seconds.
  • The desired torque signal is not received by the PCM for 3 seconds.
Action Taken When the DTC Sets
  • The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
  • The malfunction indicator lamp (MIL) will not illuminate.
  • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
Conditions for Clearing the MIL/DTC
  • A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.
  • A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL/DTC.
Diagnostic Aids

Important

Do not perform this diagnostic procedure if the customer's concern is not related to the ABS and/or the Traction Control system(s).

The following may cause an intermittent:

  • Mis-routed harness
  • Rubbed through wire insulation
  • Broken wire inside the insulation
Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step determines if the EBTCM is receiving the 5.0 volts from the PCM. Use the connector test kit adaptor when probing the EBTCM connector.

  2. If no DTCs are set, inspect connections at the EBTCM.

  3. This DTC will not report a pass. The scan tool status for this DTC will never report a pass. The scan tool will only display when the diagnostic fails. The repair is not complete if the scan tool indicates that the diagnostic ran and failed.

DTC P1571 Desired Torque Circuit

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important

Perform this diagnostic procedure only if the customer's concern is related to the ABS and/or the Traction Control system(s). Refer to ABS Diagnostic System Check for further diagnosis.

  1. Install the scan tool.
  2. Turn OFF the ignition.
  3. Disconnect the EBTCM electrical connector.
  4. Turn ON the ignition leaving the engine OFF.
  5. Probe the Desired Torque circuit at the EBTCM electrical connector using the DMM connected to ground.

Does the DMM display near the specified value?

5.0 V

Go to Step 3

Go to Step 4

3

Important

Verify communication between the scan tool and the EBTCM before you continue with this diagnostic. Refer to ABS Diagnostic System Check if you can not establish communications.

Are DTCs C1255 or C1277 (ABS/TCS DTCs) or B0844 (BCM DTC) set?

--

Go to Brakes or Body and Accessories for further diagnosis

Condition intermittent, Go to Diagnostic Aids

4

Probe the Desired Torque circuit at the EBTCM electrical connector using the DMM connected to ground.

Does the DMM display near the specified value?

B+

Go to Step 7

Go to Step 5

5

Probe the Desired Torque circuit at the EBTCM electrical connector using a test lamp connected to B+.

Is the test lamp illuminated?

--

Go to Step 8

Go to Step 6

6

  1. Check for an open in the Desired Torque circuit.
  2. If you find a problem, repair it as necessary. Refer to Body and Accessories/Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

7

Repair the short to B+ on the Desired Torque circuit. Refer to Body and Accessories/Wiring Systems.

Is the action complete?

--

Go to Step 11

--

8

Repair the short to ground on the Desired Torque circuit. Refer to Body and Accessories/Wiring Systems.

Is the action complete?

--

Go to Step 11

--

9

  1. Check the terminal connections at the PCM.
  2. If you find a problem, repair it as necessary. Refer to Body and Accessories/Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

10

Important:

Program the replacement PCM. Refer to PCM/TAC Module Replacement .

Replace the PCM.

Is the action complete?

--

Go to Step 11

--

11

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test failed?

--

Go to Step 12

Go to Step 2

12

Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to applicable DTC

System OK

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