DTC P0568 6.6L and 7.8L
Circuit Description
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 allow the vehicle to coast. The ECM 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0568 (6.6L and 7.8L) Cruise Control Set Switch Circuit
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The cruise switch is ON. |
Conditions for Setting the DTC
The ECM detects the set/coast switch is ON for longer than 90 seconds.
Action Taken When the DTC Sets
| • | The ECM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM 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
| • | 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 Conditions and Poor Connections . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Engine Control Module Connector End Views for the 6.6L (LLY) engine, or Engine Control Module Connector End Views for the 7.8L engine | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the Cruise Set/Coast Switch parameter display On? | Go to Step 3 | Go to Diagnostic Aids | |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 6 |
4 | Test the cruise control set/coast switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . 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 Conditions and Poor Connections and Connector Repairs . 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 ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the cruise control switch. Refer to Cruise Control Switch Replacement . Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
DTC P0568 8.1L
Circuit Description
The cruise control set/coast switch is an input to the throttle actuator control (TAC) module. The TAC module uses 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 the vehicle 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0568 (8.1L) Cruise Control Set Switch Circuit
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The cruise control switch is ON. |
Conditions for Setting the DTC
The PCM receives a serial data signal from the TAC module indicating that 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 control system 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
| • | Ensure that the set/coast switch is not stuck or sticking in the engaged position. |
| • | For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference : Cruise Control Schematics Connector End View Reference: Powertrain Control Module Connector End Views for the 8.1L engine | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the Cruise Set/Coast Switch parameter display On? | Go to Step 3 | Go to Diagnostic Aids | |
3 |
Does the Cruise Set/Coast Switch parameter display On? | Go to Step 4 | Go to Step 5 |
4 | Test the cruise control set/coast switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
5 | Inspect for poor connections at the harness connector of the cruise control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
6 | Inspect for poor connections at the harness connector of the throttle actuator control (TAC) module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 9 | Go to Step 7 |
7 | Replace the TAC module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the cruise control switch. Refer to Cruise Control Switch Replacement . Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC reset? | Go to Step 2 | System OK |
