Pinpoint Test I: The Traction Control System Is Inoperative

Anti-Lock Control

Pinpoint Tests

Pinpoint Test I: The Traction Control System is Inoperative

Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number

Normal Operation

Traction control utilizes ABS components to detect and control excessive rear wheel spin on low-traction surfaces. On high-traction surfaces, traction control will permit a controlled amount of rear wheel spin in the interest of quick acceleration. The traction control strategy will utilize throttle position information provided by the PCM over the High Speed Controller Area Network (HS-CAN) and front wheel speed sensor input to determine if it is necessary for traction control to intervene.

If the rear wheels begin to spin on a low-traction surface, the ABS module will use the Hydraulic Control Unit (HCU) to modulate brake fluid pressure to the rear brake calipers. At the same time, the ABS module sends a message to the PCM over the HS-CAN bus to modulate engine torque. Engine torque modulation is achieved by regulating fuel and spark to the cylinders. Once the rear wheels return to the desired speed, the ABS module stops modulating the brake fluid pressure and stops sending the message to the PCM.

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Instrument cluster
- ABS module



PINPOINT TEST I: THE TRACTION CONTROL SYSTEM IS INOPERATIVE

NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.

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I1 CHECK HS-CAN BUS


- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Network Test.
- Using the scan tool, carry out the network test. Retrieve and record any DTCs.
- Does the network test fail or are any communication DTCs present?

Yes
REFER to Information Bus to diagnose the communication concern.

No
GO to I2.

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I2 CHECK FOR INSTRUMENT CLUSTER DTCs


- Enter the following diagnostic mode on the scan tool: Self Test Instrument Cluster.
- Using the scan tool, carry out the instrument cluster self-test. Retrieve and record any instrument cluster DTCs.
- Are any instrument cluster DTCs present?

Yes
GO to the Instrument Cluster DTC Chart. Instrument Cluster DTC Chart

No
GO to I3.

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I3 CHECK FOR ABS MODULE DTCs


- Enter the following diagnostic mode on the scan tool: Self Test ABS.
- Using the scan tool, carry out the ABS module self-test. Retrieve and record any ABS module DTCs.
- Are any ABS module DTCs present?

Yes
GO to the ABS Module DTC Chart. ABS Module DTC Chart

No
GO to I4.

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I4 CHECK FOR CORRECT ABS MODULE OPERATION


- Ignition OFF.
- Disconnect: ABS Module C135.
- Check the connector for:
- corrosion.
- spread terminals.
- pushed-out pins.
- Connect: ABS Module C135.
- Make sure the connector seats properly, then operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSPECT the wheel speed sensor tone ring for damage and looseness. INSTALL new components as necessary. If the tone ring is OK, INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module Service and Repair. CLEAR the DTCs. REPEAT the self-test.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.

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