Circuit Description
The cruise set/coast switch is an input to the fuel control portion of the PCM. These inputs allow the PCM to control and hold a requested speed. The cruise set/coast switch sends an ignition voltage signal to the PCM when the set/coast switch is ON.
Conditions for Running the DTC
| • | The PCM performs this DTC diagnostic continuously. |
| • | The ignition switch in the ON position. |
Conditions for Setting the DTC
Ignition voltage on set/coast request signal circuit when the cruise control ON/OFF switch in the OFF position.
or
| • | Set/Coast request switch ON for longer than 25.5 seconds when the Cruise Control ON/OFF switch in the ON position. |
| • | All of the diagnostic set conditions met for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM disallows all cruise control inputs. |
| • | TCC shift schedules may be affected. |
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information stores in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | The use of a scan tool. |
Diagnostic Aids
If the set/coast switch is stuck in the ON position or the driver is holding the set/coast switch ON for longer than 25.5 seconds, DTC P0568 will set. DTC P0568 only checks the signal circuit for a short to voltage.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This step determines if the problem is intermittent.
-
This step determines if the signal circuit is shorted to voltage.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform A Diagnostic System Check - Cruise Control? | Go to Step 2 | |
Did the cruise control set/coast switch parameter change state? | Go to Diagnostic Aids | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 6 | |
4 | Test the cruise control set/coast 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 Conditions 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 PCM. Refer to Testing for Intermittent Conditions 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, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column. Did you complete the repair? | Go to Step 9 | -- |
8 |
Important: The PCM must be reprogrammed after replacement. Refer to Powertrain Control Module Programming in Engine Controls - 6.5L. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 6.5L. Did you complete the repair? | Go to Step 9 | -- |
9 | Operate the vehicle within the conditions for cruise control operation. Does the cruise control system operate correctly? | System OK | Go to Step 2 |
