Test D: Inaccurate Mph Reading
- Turn ignition switch to LOCK position. Connect NGS tester (418-F052). Select instrument cluster active command SPDOMETER. Scroll to 0, 50 and 100 percent. If speedometer displays 0 at zero percent and half the speedometer display at 50 percent and top speed at 100 percent speedometer is working but not receiving a speed signal from PCM. See SELF-DIAGNOSTICS - EEC-V - GASOLINE & NGV article in ENGINE PERFORMANCE. If speedometer does not display 0 at zero percent and half the speedometer display at 50 percent and top speed at 100 percent, go to next step.
- Turn ignition switch to LOCK position. Check for corrosion, pushed out pins and connectors that are not connected properly. Repair any damage found and reconnect any loose connectors. Operate system. If problem still exists, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Configure replacement instrument cluster, see MODULE COMMUNICATIONS NETWORK article. If problem does not exist, system is operating properly at this time. Clear DTCs and retest.