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Test 8: Speedometer Inaccurate Or Operative

  1. Perform INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK before proceeding. See INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK  under SYSTEM TEST. If INSTRUMENT PANEL CLUSTER (IPC) DIAGNOSTIC SYSTEM CHECK has been performed, go to next step.
  2. Turn ignition switch to OFF position. Connect scan tool to Data Link connector (DLC). Raise and support vehicle sufficiently for drive wheels to rotate. Turn ignition switch to ON position. Using scan tool, select POWERTRAIN, ENGINE DATA, then DATA. Start engine and place gear selector in Drive. Compare vehicle speed displayed on scan tool with speedometer reading. If scan tool does not agree with speedometer, turn engine off, then go to next step. If scan tool agrees with speedometer, turn engine off, then check for an intermittent problem caused by poor connections, a break in wire insulation, or a broken wire inside insulation. See WIRING DIAGRAMS .
  3. Using a Digital Multimeter (DMM) in AC voltage scale, select Frequency. Remove IPC. See INSTRUMENT PANEL CLUSTER (IPC)  under REMOVAL & INSTALLATION. Using DMM connected to ground, backprobe IPC connector terminal A3, vehicle speed signal circuit (Dark Green/White wire). Start engine and place gear selector in Drive. Monitor DMM while running vehicle up to 20 MPH (as displayed on scan tool). If frequency is 18-25 Hz, go to next step. If frequency is not 18-25 Hz, go to step  5.
  4. Replace IPC. See INSTRUMENT PANEL CLUSTER (IPC)  under REMOVAL & INSTALLATION. After repair, go to step  6.
  5. Check for a break in wire insulation or a broken wire inside insulation, and for loose or poor connections at all related components which could cause an intermittent problem. See WIRING DIAGRAMS . After repair, go to next step.
  6. Road test vehicle to check speedometer operation. If system operates properly, system is okay. If speedometer does not operate properly, return to step  3.
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