GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P1571 Traction Control Torque Request Circuit

Object Number: 475479 Size: SF
Engine Controls Components
Generator, EBCM, Oil level and Auto Trans Shift Lock Control Switches
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The traction control system uses the antilock brake system in conjunction with the PCM fuel and ignition controls to limit drive wheel slippage during acceleration. The PCM controlled portion of the traction control system reduces engine torque by any or all of the following methods:

    • Retarding spark timing
    • Altering air/fuel ratio
    • Shutting OFF up to three injectors

To determine the amount of torque reduction required, the PCM monitors the traction control system (TCS) Desired Torque pulse width modulation (PWM) signal from the electronic brake and traction control module (EBCM). The PCM also provides a TCS Delivered Torque PWM informing the EBCM how much torque is being produced by the engine. The Desired Torque display on the scan tool indicates the amount of engine torque requested by the EBCM. With traction control not active, Desired Torque should be approximately 90 percent. The Desired Torque display on the scan tool is not the PWM duty cycle.

Conditions for Running the DTC

The traction control is active.

Conditions for Setting the DTC
    • The desired torque signal PWM duty cycle is less than 5 percent or more than 95 percent.
    • The conditions exists for up to 10 seconds

Action Taken When the DTC Sets

    • The PCM does not illuminate the malfunction indicator lamp (MIL).
    • The PCM stores the conditions that were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.
    • DTC can be cleared by using the scan tool Clear Information function or by disconnecting the PCM battery feed.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a broken wire inside the insulation. Check for the following conditions:

    • A faulty connection or a damaged harness--Inspect the PCM harness for an open or a short to ground in the desired torque PWM circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and a damaged harness. Use a corresponding mating terminal to test for proper terminal tension.
    • Intermittent Test
        Using a scan tool, observe Desired Torque display while moving the related connectors and wiring harnesses. If the failure is induced, the displayed value will change. This may help to isolate the location of the malfunction.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that set the DTC. This may assist in diagnosing the condition.

DTC P1571 - TCS Desired Torque Circuit

Step

Action

Values

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn ON the ignition switch.
  2. Observe the Traction Control Desired Torque display on the scan tool.

Is Traction Control Desired Torque at or near the specified value?

100%

Go to Step 4

Go to Step 3

3
  1. Turn OFF the ignition switch.
  2. Disconnect the electronic brake and traction control module (EBCM).
  3. Turn ON the ignition switch.
  4. Using a DMM, measure the voltage between the TCS desired torque circuit at the EBCM harness connector and ground.

Does the voltage measure the specified value?

5 V

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition switch.
  2. Connect J 39700 ABS/TCS Pinout Box and J 39700-300 to the EBCM and to the EBCM harness connector.
  3. Connect the DMM to measure the AC frequency between the TCS desired torque circuit and ground.
  4. Turn ON the ignition switch.
  5. Observe the frequency on the DMM.

Is the frequency between the specified values?

120-135 Hz

Go to Step 5

Go to Step 7

5
  1. Set the DMM to the % duty cycle.
  2. Connect the DMM to measure the duty cycle between the TCS desired torque circuit and ground.
  3. Turn ON the ignition switch.
  4. Observe duty cycle on the DMM.

Is duty cycle between the specified values?

5-95%

Go to Step 9

Go to Step 7

6
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Turn ON the ignition switch.
  4. Check the TCS desired torque circuit for an open, a short to ground, or a short to voltage.
  5. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 11

Go to Step 9

7
  1. Check for a poor connection at the EBCM.
  2. If a problem is found, repair as necessary. Refer to the following procedures:
    3. •  Connector Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 11

Go to Step 8

8

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Is the action complete?

--

Go to Step 11

--

9
  1. Check for a poor connection at the PCM.
  2. If a problem is found, repair as necessary. Refer to the following procedures:

Was a problem found?

--

Go to Step 11

Go Step 10

10

Important:: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming

Is the action complete?

--

Go to Step 11

--

11
  1. Clear the DTCs.
  2. Turn ON the ignition switch.
  3. Observe the Traction Control Desired Torque on the scan tool.

Is the Traction Control Desired Torque at or near the specified value?

100%

System OK

Go to Step 2