For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Instrument Cluster Schematics
1 | Did you perform the Instrument Cluster Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Instrument Cluster
2 |

1. Disconnect the PCM connector C2.
2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the vehicle speed signal circuit and a good ground.
3. Turn the ignition ON, with the engine OFF.
4. Set the J 33431-C to generate a speedometer signal.

Does the speedometer briefly display 88.5 km/h (55 mph)?

Go to Step 6

Go to Step 3

3 | Test the vehicle speed signal circuit for an open or for a high resistance between the IPC and the PCM. 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 4
4 | Test the speedometer ground circuit for an open or for a high resistance. 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 5
5 | Inspect for poor connections at the harness connector of the 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 7
6 | 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 9 | Go to Step 8
7 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement? | Go to Step 9 | --
8 | Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L or to the Cat® Medium Duty Diesel Engine Manual - LG5. Did you complete the replacement? | Go to Step 9 | --
9 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2