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 PCM via the UART 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
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 in Wiring Systems.
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: Cruise Control Connector End Views , Powertrain Control Module Connector End Views in Engine Controls-4.8L.5.3L, and 6.0L, or Powertrain Control Module Connector End Views in Engine Controls-8.1L | |||||||
1 | Did you perform the Cruise Control Diagnostic System Check? | Go to Step 2 | |||||
2 | Is DTC P1518 current in the PCM? | Go to DTC P1518 in Engine Controls-4.8L, 5.3L, and 6.0L or to DTC P1518 in Engine Controls-8.1L | Go to Step 3 | ||||
Does the Cruise Set/Coast Switch parameter display On? | Go to Step 4 | Go to Diagnostic Aids | |||||
4 |
Does the Cruise Set/Coast Switch parameter display On? | Go to Step 5 | Go to Step 6 | ||||
5 | Test the cruise control set/coast switch signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 | ||||
6 | Inspect for poor connections at the harness connector of the cruise control switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 | ||||
7 | Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 | ||||
8 | Replace the TAC module. Refer to the appropriate procedure:
Did you complete the replacement? | Go to Step 10 | -- | ||||
9 | Replace the cruise control switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | Go to Step 10 | -- | ||||
10 |
Does the DTC reset? | Go to Step 2 | System OK | ||||
