Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle |
| • | Review Strategy Based Diagnosis |
DTC Descriptor
DTC P0568: Cruise Control Set Switch CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | 1 | 1 | -- | -- |
Cruise Control ON/OFF Switch Signal | 1 | 1 | P0565 | -- |
Cruise Control Resume/Accel Switch Signal | 1 | 1 | P0567 | -- |
Cruise Control Set/Coast Switch Signal | 1 | 1 | P0568 | -- |
1. Cruise Control malfunction | ||||
Circuit Description
6.6L and 7.8L
The cruise control set/coast switch is an input to the engine control module (ECM). The ECM monitors the cruise control set/coast switch signal circuit in order to detect when the driver has requested to set the vehicle speed or to decelerate from the currently set speed. The ECM module detects a voltage signal on the cruise control set/coast switch signal circuit when the switch is applied. This DTC sets if the ECM detects that voltage is present on the cruise control set/coast switch signal circuit for longer than 90 seconds.
8.1L
The cruise control set/coast switch is an input to the throttle actuator control (TAC) module. The TAC module monitors the cruise control set/coast switch signal circuit in order to detect when the driver has requested to set the vehicle speed or to decelerate from the currently set speed. The TAC module detects a voltage signal on the cruise control set/coast switch signal circuit when the switch is applied. The TAC module sends a serial data signal to the powertrain control module (PCM) via the serial data circuit. This DTC sets if the PCM receives a serial data signal from the TAC module indicating that voltage is present on the cruise control set/coast switch signal circuit for longer than 90 seconds.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The cruise control switch is ON. |
Conditions for Setting the DTC
6.6L and 7.8L
The ECM detects that the set/coast switch circuit is active for longer than 90 seconds.
8.1L
The PCM receives a serial data signal from the TAC module indicating that the set/coast switch circuit is active for longer than 90 seconds.
Actions Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The cruise control system is disabled. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear after 40 malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cruise Control Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Engine ON, while rotating the steering wheel to both steering stops, observe the scan tool Cruise Control Switch parameter while pressing each of the cruise control switches. The parameter should toggle between ON, OFF, Resume, Set, as the applicable switch is pressed.
Circuit/System Testing
- Ignition OFF, disconnect the X201 harness connector at the turn signal/multifunction switch. With the turn signal/multifunction switch harness connectors removed from the column bulkhead connector, reconnect the steering column bulkhead connector X201.
- Ignition ON, test for B+ between the B+ circuit terminal A13 and ground.
- Install a 3A fused jumper wire between the signal circuit terminal A12 and B+ circuit terminal A13. Verify the scan tool cruise ON/OFF switch parameter displays ON.
- Verify the scan tool cruise Set/Coast switch parameter displays Inactive.
- Verify the scan tool cruise Resume/Accel. switch parameter displays Inactive.
- Install a 3A fused jumper wire between the signal circuit terminal A14 and B+ circuit terminal A13. Verify the scan tool cruise Set/Coast switch parameter displays Active.
- Install a 3A fused jumper wire between the signal circuit terminal A15 and B+ circuit terminal A13. Verify the scan tool cruise Resume/Accel. switch parameter displays Active.
- If all circuit tests normal, replace the turn signal/multifunction switch.
| ⇒ | If less than specified value, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If not in the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM or TAC. |
| ⇒ | If not the specified value, test the signal circuit terminal A14 for a short to voltage, if the circuit tests normal, replace the ECM or TAC. |
| ⇒ | If not the specified value, test the signal circuit terminal A15 for a short to voltage, If the circuit tests normal, replace the ECM or TAC. |
| ⇒ | If not in the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM or TAC. |
| ⇒ | If not in the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM or TAC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM or TAC module replacement, setup, and programming |
