GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2005 🢒 Ascender - 2WD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0654

Circuit Description

The powertrain control module (PCM) creates the engine speed signal by pulsing the circuit to ground. The PCM monitors the voltage on the engine speed signal circuit. If the PCM determines that the voltage is not within the normal operating range, the PCM sets a DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0654 Engine Speed Output Circuit

Conditions for Running the DTC
    • The engine speed is greater than 400 RPM.
    • The ignition voltage is greater than 6 volts, but less than 18 volts.

Conditions for Setting the DTC
    • The PCM detects that the commanded state of the driver and the actual state of the signal circuit do not match.
    • The above condition exists for a minimum of 5 seconds.

Action Taken When the DTC Sets
    • The PCM stores the DTC information in memory when the diagnostic test runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The PCM records the operating conditions at the time when the diagnostic test fails. The PCM stores this information in the Failure Records.

Conditions for Clearing the MIL/DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • A history DTC is cleared after 40 consecutive malfunction free warm-up cycles.
    • The PCM receives the clear code command from the scan tool.

Step

Action

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Instrument Panel, Gages, and Console Connector End Views , Powertrain Control Module Connector End Views in Engine Controls - 4.2L, or Engine Control Module Connector End Views in Engine Controls - 5.3L

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Start the engine.
  3. With the scan tool, observe the Engine Speed parameter in the powertrain control module (PCM) Engine Data 3 data list.

Does the Engine Speed parameter match the tachometer display?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. Turn the ignition OFF.
  2. Disconnect the following PCM connector:
  3. Install one J 33431-C Signal Generator and Instrument Panel Tester lead to the engine speed signal circuit at the PCM harness connector, and connect the other lead to a good ground.
  4. Turn the ignition ON, with the engine OFF.
  5. Set the J 33431-C to generate a tachometer signal.

Does the vehicle tachometer indicate an RPM reading?

Go to Step 5

Go to Step 4

4

Test the engine speed signal circuit for a short to voltage or 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 9

Go to Step 6

5

Inspect for poor connections at the PCM connector. 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 9

Go to Step 7

6

Inspect for a 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 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
  1. Use the scan tool in order to clear the DTCs.
  2. Operate vehicle within the Conditions for Running this DTC.

Does the DTC reset?

Go to Step 2

System OK