Circuit Description
The powertrain control module (PCM) creates the vehicle speed signal by pulsing the signal circuit to ground. The PCM pulses the circuit at the same rate as the vehicle speed signal input. The PCM monitors the voltage on the vehicle speed signal circuit. If the PCM determines the voltage is out of the normal operating range, a DTC sets.
Conditions for Running the DTC
| • | The engine speed is greater than 400 RPM. |
| • | The ignition voltage is between 9 volts and 16 volts. |
Conditions for Setting the DTC
| • | The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match. |
| • | The condition must be present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
| • | The cruise control system is disabled. |
| • | The PCM stores a DTC P0608 in memory. |
| • | The PCM records the operating conditions at the time the DTC sets. The PCM displays the failure information in the Failure Records on the scan tool. |
Conditions for Clearing the DTC
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The PCM receives the clear code command from the scan tool. |
Diagnostic Aids
| • | If any additional powertrain DTCs are stored, refer to Diagnostic Trouble Code (DTC) List in Engine Controls-3.8 L (L26 and L32). |
| • | For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views or Powertrain Control Module Connector End Views in Engine Controls 3.8 L (L26 and L32) | ||||
1 | Did you perform the Cruise Control Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the Vehicle Speed Sensor parameter indicate any vehicle speed? | -- | Go to Step 4 | Go to Step 3 |
3 | Is DTC P0502 or P0503 current in the PCM? | -- | Go to Diagnostic Aids | Go to Step 7 |
4 |
Does the voltage measure greater than the specified value? | 8.5 V | Go to Step 5 | Go to Step 6 |
5 | Test the vehicle speed 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 11 | Go to Step 8 |
6 | Test the vehicle speed signal circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 |
7 | Inspect for poor connections at the harness connector of the PCM. 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 11 | Go to Step 9 |
8 | 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 to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
9 |
Important:: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.8 L (L26 and L32). Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the TAC module. Refer to Throttle Body Assembly Replacement in Engine Controls - 3.8 L (L26 and L32). Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
