The powertrain control module (PCM) creates the vehicle speed output signal by pulsing the 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.
This diagnostic procedure supports the following DTC:
DTC P0608 Vehicle Speed Output Circuit
• | The engine speed is more than 400 RPM. |
• | The ignition voltage is between 6-18 volts. |
• | The PCM detects that the voltage of the vehicle speed signal circuit is out of the normal operating range. |
• | The condition must be present for a minimum of 5 seconds. |
• | The PCM stores the DTC information in memory when the diagnostic runs and fails. |
• | The PCM records the operating conditions at the time the diagnostic fails. The PCM displays the failure information in the Failure Records on the scan tool. |
• | 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. |
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Powertrain Control Module Connector End Views in Engine Controls - 4.3L or Instrument Panel, Gages, and Console Connector End Views | |||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the Vehicle Speed Sensor parameter match the speedometer display? | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
3 |
Does the vehicle speedometer indicate approximately 55 mph (89 km/h)? | Go to Step 5 | Go to Step 4 |
4 | Test the vehicle speed signal circuit for an open, for a short to voltage, or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 6 |
5 | Inspect for poor connections at the PCM connector. 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 instrument panel cluster (IPC). 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 PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 9 | -- |
8 | Replace the IPC. Refer to Control Module References in Computer/Integrating Systems 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 |