Circuit Description
The traction control system uses the antilock brake system in conjunction with the powertrain control module (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 boost PWM (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 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 vary between 99-100 percent. The Desired Torque display on the scan tool is not the PWM duty cycle.
Conditions for Setting the DTC
| • | 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 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 broken wire inside the insulation. Inspect for the following conditions:
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.
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
2 |
Does the Traction Control Desired Torque measure at or near the specified value? | 100% | ||
3 |
Does the voltage measure at the specified value? | 5 V | ||
4 |
Does the frequency measure between the specified values? | 120-135 Hz | ||
5 |
Does the duty cycle measure between the specified values? | 5-95 % | ||
6 |
Did you find and correct the condition? | -- | ||
7 |
Did you find and correct the condition? | -- | ||
8 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System. Is the action complete? | -- | -- | |
9 |
Did you find and correct the condition? | -- | ||
10 |
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
11 |
Does the Traction Control Desired Torque measure at or near the specified value? | 100% | System OK |
