Test U: Incorrect Tachometer Indication
WARNING: This page is about a different car, the 2000 Ford Mustang and 1999 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, select instrument cluster active command TCHOMETER. Trigger, monitor and scroll TCHOMETER at 0%, 50% and 100%. Tachometer should indicate 0 RPM at 0%, middle RPM at 50% and maximum RPM at 100%. If tachometer responds as specified, repair engine speed input from PCM (retrieve codes from PCM). See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If tachometer does not respond as specified, replace instrument cluster.