Speedometer/Odometer Inaccurate (SHO)

Connect NGS tester to Data Link Connector (DLC). Road test vehicle and monitor speed on NGS tester. If the speedometer is operating and NGS tester registers speed, go to next step. If speedometer is not operating and no speed signal exists, go to step 5).
Drive vehicle over a known, measured distance. If odometer is reading accurately, go to next step. If inaccurate, go to step 4).

Drive vehicle at a steady speed over a known measured distance and record time taken to travel that distance. If speedometer meets speedometer calibration tolerance specifications, system is okay. See SPEEDOMETER CALIBRATION TOLERANCE table. If speedometer fails to meet speedometer calibration tolerance, replace speedometer assembly.

SPEEDOMETER CALIBRATION TOLERANCE ⁽¹⁾

Actual Speed-MPH

Allowable Range-MPH

27.7-34.5

57.4-64.1

⁽¹⁾	Odometer measured over actual 10 miles: 9.6-10.3 miles.

Using NGS tester, access SARC PID. Select VSS_SRC from PID menu. Monitor vehicle speed on tester, while test driving vehicle. If vehicle speed shown on tester is approximate vehicle speed, go to next step. If vehicle speed shown on tester is not approximate vehicle speed, repair circuit No. 679 (Gray/Black wire).
With an ohmmeter connected to ground, measure resistance of circuit No. 679 (Gray/Black wire) at ABS control module connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair circuit No. 679 (Gray/Black wire) for open circuit and retest system.
With an ohmmeter connected to ground, measure resistance of circuit No. 398 (Black/Yellow wire) at instrument cluster connector C250 terminal No. 8. See Figure - Figure . If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair circuit No. 398 (Black/Yellow wire) for open circuit and retest system.
Disconnect cluster connectors C250 and C251. With an ohmmeter check speedometer for continuity from contact clips to printed circuit. If there is continuity at all clips, go to next step. If there is no continuity, replace contact clips and retest system.

Reconnect cluster connectors. Check continuity from speedometer contact clips to cluster connector terminals. See PRINTED CIRCUIT CHECK table.

PRINTED CIRCUIT CHECK

Cluster Connector	Circuit No. (Wire Color)	Function
C251-10	1044 (WHT/YEL)	Power Input (RUN)
C250-1	57 (BLK)	GROUND
C251-16	679 (GRY/BLK)	VSS Input Signal

If there is continuity in all circuits, replace speedometer assembly and retest system. See SPEEDOMETER under REMOVAL & INSTALLATION. If continuity is not present in all circuits, replace instrument cluster printed circuit and retest system. See PRINTED CIRCUIT under REMOVAL & INSTALLATION.