Circuit Description
The engine control module (ECM) creates the engine speed output signal by pulsing the circuit to ground. The ECM monitors the voltage on the engine speed output circuit. If the ECM determines that the voltage is out of the normal operating range, a DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0654 Engine Speed Output Circuit
Conditions for Running the DTC
| • | The engine is running. |
| • | The ignition 1 voltage is more than 10 volts. |
| • | This DTC runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects that the commanded state of the driver and the actual state of the signal circuit do not match. |
| • | The above condition must be present for a minimum of 25 seconds. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Component Connector End Views | |||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||
2 |
Does DTC P0654 fail this ignition? | Go to Step 4 | Go to Step 3 | ||||||||||
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||||||
4 | Are DTCs P0656 and P1668 also set? | Go to Step 7 | Go to Step 5 | ||||||||||
5 |
Does the tachometer display an engine speed? | Go to Step 9 | Go to Step 6 | ||||||||||
6 | Test the engine speed signal circuit for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 10 | ||||||||||
7 | Test the ignition 1 voltage circuit of the instrument panel cluster (IPC) for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 8 | ||||||||||
8 | Test the ground circuit of the IPC for an open circuit or for high resistance. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 10 | ||||||||||
9 | Inspect for poor connections at 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 13 | Go to Step 11 | ||||||||||
10 | Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 12 | ||||||||||
11 | Replace the ECM. Refer to Control Module References for ECM replacement, setup and programming. Did you complete the replacement? | Go to Step 13 | -- | ||||||||||
12 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement? | Go to Step 13 | -- | ||||||||||
13 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 14 | ||||||||||
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |||||||||||
