Circuit Description
The engine control module (ECM) creates the vehicle speed signal by pulsing the signal circuit to ground at a rate of 4,000 PPM. The instrument panel cluster (IPC) converts the 4,000 PPM signal to a speedometer position. The IPC also receives a class 2 message from the ECM indicating the vehicle speed. The IPC uses this class 2 message for diagnostic purposes.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0608 Vehicle Speed Output Circuit
Conditions for Running the DTC
| • | The IPC receives a class 2 message from the ECM indicating that the vehicle speed is greater than 10 km/h (6 mph). |
| • | The ignition voltage is between 9-18 volts. |
Conditions for Setting the DTC
| • | The IPC does not detect a 4K PPM signal on the vehicle speed signal circuit. |
| • | The condition above must be present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
The IPC stores a DTC B0540 in memory.
Conditions for Clearing the DTC
| • | The history DTC clears after 100 malfunction-free warm-up cycles. |
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The IPC receives the clear code command from the scan tool. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the voltage measure greater than the specified value? | 9 V | Go to Step 3 | Go to Step 4 |
3 | Test the vehicle speed signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 |
4 | Test the vehicle speed signal circuit for an open or for a short to ground. Refer to Circuit Testing and to 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 ECM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
6 | Inspect for poor connection at the harness connector of the instrument panel cluster (IPC). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
7 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the IPC. 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 |
