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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1516 (Instrument Panel System Displays, Gauges And Console) >> Diagnostic Information and Procedures >> Speedometer and/or Odometer Inaccurate or Inoperative >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The number(s) below refer to the step number(s) on the diagnostic table.

  1. 4:  This step tests for the proper vehicle speed signal from the PCM.
Speedometer and/or Odometer Inaccurate or Inoperative

Step Action Value(s) Yes No
Schematic Reference:  Instrument Cluster Schematics  
1 Did you perform the IPC Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Instrument Cluster 
2
  1. Install a scan tool.
  2. Raise the vehicle's drive wheels. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Start the engine.
  4. Place the transmission into drive for automatic transmission and third gear for manual transmission.
  5. With the scan tool, observe the Vehicle Speed parameter in the PCM Engine Data 1 data list.
Does the Vehicle Speed parameter match the speedometer display?		 - Go to Step 3  Go to Step 4 
3 Does the odometer operate properly? - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 8 
4 
  1. Turn the ignition OFF.
  2. Disconnect the PCM connector C2.
  3. Turn the ignition ON, with the engine OFF.
  4. Measure the voltage from the vehicle speed signal circuit to a good ground.
Does the voltage measure greater than the specified value?		 9.6 V Go to Step 6  Go to Step 5 
5 Test the vehicle speed signal circuit for an open, a short to ground, or a high resistance between the IPC and the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 10  Go to Step 7 
6 Inspect for poor connections at the harness connector of the 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 10  Go to Step 8 
7 Inspect for poor connections at the harness connector of the PCM. 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 10  Go to Step 9 
8 Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement .
Did you complete the replacement?		 - Go to Step 10  -
9
IMPORTANT: Program the replacement PCM.
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.Did you complete the replacement?		 - Go to Step 10  -
10 Operate the system in order to verify the repair.
Use the scan tool in order to clear the DTC's that may have set in other modules during diagnosis.
Did you correct the condition?		 - System OK Go to Step 2 
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