DTC P0568

Circuit Description

The cruise control Set/Coast switch is an input to the throttle actuator control (TAC) module. The cruise control information is supplied to the PCM via serial data. This input allows the PCM and TAC module to control and hold a requested speed. The cruise control Set/Coast switch sends a ignition positive voltage signal to the TAC module when the momentary switch is applied. This DTC sets if the TAC module senses a voltage on the Set/Coast switch signal circuit when the voltage is not expected.

Conditions for Running the DTC

The Cruise switch is ON.

Conditions for Setting the DTC

The TAC module detects the Set/Coast switch is ON for longer than 90 seconds.

Action Taken When the DTC Sets

The 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.
The cruise is disabled.

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

Remove any debris from the TAC module connector surfaces before servicing the TAC module. Inspect the TAC module connector gaskets when diagnosing/replacing the module. Ensure that the gaskets are installed correctly.
For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.
Inspect for a set/coast switch stuck in the engaged position or the signal circuit is shorted to voltage.
For an intermittent, refer to Testing for Intermittent and Poor Connections in Wiring Systems.

Test Description

The number below refers to the step number on the diagnostic table.

This step determines if condition is present.

Step	Action	Yes	No
Schematic Reference: Cruise Control Schematics
1	Did you perform A Diagnostic System Check - Cruise Control?	Go to Step 2	Go to Diagnostic System Check - Cruise Control
2	Important If DTC P1518 is also set, diagnose P1518 first. Install a scan tool. Turn ON the ignition with the engine OFF. Turn OFF the cruise control switch. Observe the cruise control Set/Coast switch parameter in the PCM data list. Does the scan tool parameter indicate that the cruise control Set/Coast switch is ON?	Go to Step 3	Go to Diagnostic Aids
3	Turn OFF the ignition. Disconnect the appropriate TAC module harness connector. Turn On the ignition with the engine OFF. Monitor the cruise control Set/Coast switch parameter with a scan tool. Does the scan tool indicate that the Cruise Set/Coast switch is ON?	Go to Step 6	Go to Step 4
4	Test the cruise control ON switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 9	Go to Step 5
5	Inspect for poor connections at the harness connector of the cruise control switch. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 9	Go to Step 7
6	Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 9	Go to Step 8
7	Replace the cruise control switch. Refer to Multifunction Turn Signal Lever Replacement - On Vehicle in Steering Wheel and Column - Tilt. Did you complete the replacement?	Go to Step 9	--
8	Replace the TAC module. Refer to Accelerator Pedal Position (APP) Sensor Replacement in Engine Controls-3.8L Did you complete the replacement?	Go to Step 9	--
9	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	Go to Step 2	System OK