Test C: Speedometer Gauge &/Or Odometer Inaccurate/Inoperative

If vehicle has been checked for DTCs, go to next step. If vehicle has not been checked for DTCs, check for DTCs. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
Connect scan tool to DLC. DLC is located under instrument panel, to right of steering wheel. Test drive vehicle. Using scan tool, monitor vehicle speed. If speed displayed on scan tool and speed displayed on speedometer are similar, go to next step. If speed displayed on scan tool and speed displayed on speedometer are not similar, go to step 6 .
If both speedometer and odometer are inaccurate, go to next step. If both speedometer and odometer are not inaccurate, go to step 7 .
Inspect vehicle for correct tire size, PCM calibration and vehicle speed sensor application. If concern exists, go to next step. If concern does not exist, perform powertrain on-board self-diagnostic system check. See appropriate BODY CONTROL MODULES article.
Replace tires or vehicle speed sensor, or recalibrate PCM as necessary. Recheck system operation. If concern still exists, go to next step.
If all other vehicle speed-related systems are operating properly, go to next step. If one or more vehicle speed-related system does not operate properly, perform powertrain diagnostic system check. See appropriate BODY CONTROL MODULES article.
Check for open short to ground or short to voltage in Dark Green wire between PCM connector C1 terminal 55 and instrument cluster harness connector. See WIRING DIAGRAMS . If concern exists, go to next step. If concern does not exist, go to step 9 .
Repair Dark Green wire between PCM and instrument cluster as necessary.
Inspect instrument cluster for poor connections. If concern exists, repair as necessary. If concern does not exist, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION.