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For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 LeSabre 🢒 DTC 🢒 DTC P1571 Traction Control Torque Request Circuit

Object Number: 399922 Size: SF
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description 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.
    • Altering supercharger boost (VIN 1).
    • Shutting OFF up to three injectors.

To determine the amount of torque reduction required, the PCM monitors the TCS Desired Torque PWM signal from the Electronic Brake and Traction Control Module (EBTCM). The PCM also provides a TCS Delivered Torque signal informing the Electronic Brake and Traction Control Module (EBTCM) how much torque is being produced by the engine. The Traction Control Desired Torque display on the scan tool indicates the amount of engine torque requested by the EBTCM. With traction control not active, Traction Control Desired Torque should vary between 99% and 100%. The Traction Control Desired Torque percentage displayed on the scan tool is not the PWM duty cycle.

Conditions for Running the DTC

Traction control is active.

Conditions for Setting the DTC
  1. Desired torque signal PWM duty cycle is less than 5% or greater than 95%.
  2. The conditions exists for up to 10 seconds

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

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

    • Poor Connection or Damaged Harness.
        Inspect PCM harness for an open or short to ground in the desired torque PWM circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
    • Intermittent Test.
        Using a scan tool, observe Desired Torque display while moving related connectors and wiring harness. 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 that caused the DTC to be set occurs. This may assist in diagnosing the condition.

DTC P1571 - TCS Desired Torque Circuit

Step

Action

Value(s)

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 (EBTCM).
  3. Turn ON the ignition switch.
  4. Using a DMM, measure voltage between the TCS Desired Torque circuit at the EBTCM harness connector and ground.

Does voltage measure the specified value?

5V

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition switch.
  2. Connect J 39700-25 ABS/TCS Pinout Box and Adapter to the EBTCM and to the EBTCM harness connector.
  3. Connect the DMM to measure AC frequency between the TCS Desired Torque circuit and ground.
  4. Turn ON the ignition switch.
  5. Observe frequency on the DMM.

Is frequency between the specified values?

120 -135 Hz

Go to Step 5

Go to Step 7

5
  1. Set the DMM to % duty cycle.
  2. Connect the DMM to measure 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 EBTCM.
  2. If a problem is found, repair as necessary. Refer to Intermittents and Poor Connections Diagnosis .

Was a problem found?

--

Go to Step 11

Go to Step 8

8

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

Is the action complete?

--

Go to Step 11

--

9

Check for a poor connection at the PCM.

If a problem is found, repair as necessary. Refer to Intermittents and Poor Connections Diagnosis .

Was a problem found?

--

Go to Step 11

Go Step 10

10

Important:: The replacement PCM must be programmed.

Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is 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