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For 1990-2009 cars only

Speedometer and/or Odometer Inaccurate or Inoperative L18, Late LG5

Step

Action

Value(s)

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 lead to the vehicle speed signal circuit and the other lead to a good ground.
  3. Turn the ignition ON, with the engine OFF.
  4. Set the J 33431-C to generate a speedometer signal. The speedometer signal should briefly drive the speedometer to 55 mph (88.5 km/h).

Does the speedometer briefly indicate the correct speed?

--

Go to Step 6

Go to Step 3

3

Test the vehicle speed signal 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 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 - L18 8.1L or Cat® Medium Duty Diesel Engine Manual - LG5 7.2L.

--

Go to Step 9

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9

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2

Speedometer and/or Odometer Inaccurate or Inoperative Early LG5

Step

Action

Value(s)

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 speedometer adapter connector.
  2. Connect the J 33431-C lead to the vehicle speed signal circuit and the other lead to a good ground.
  3. Turn the ignition ON, with the engine OFF.
  4. Set the J 33431-C to generate a speedometer signal. The speedometer signal should briefly drive the speedometer to 55 mph (88.5 km/h).

Does the speedometer briefly indicate the correct speed?

--

Go to Step 8

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the IPC connector.
  3. Turn the ignition ON, with the engine OFF.
  4. Measure the voltage from the ignition 1 voltage circuit to the speedometer ground circuit.

Does the voltage measure greater than the specified value?

9.0 V

Go to Step 4

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 7

5

Test the ignition 1 voltage circuit for an open, for a short to ground 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 11

Go to Step 6

6

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 11

Go to Step 7

7

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 11

Go to Step 9

8

Inspect for poor connections at the harness connector of the speedometer adapter. 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 11

Go to Step 10

9

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

--

Go to Step 11

--

10

Replace the speedometer adapter. Refer to Vehicle Speed Sensor Module Replacement .

Did you complete the replacement?

--

Go to Step 11

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11

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2