Diagnosis & Repair

Test drive vehicle and check operation of speedometer. If speedometer is not functioning correctly, see the INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section. If speedometer is functioning correctly, go to next test.
Access ECM behind glove box. Ensure ignition is off. Disconnect cruise control ECU connector (Green). Cruise control ECU is behind right kick panel. Ensure shift lever is in neutral. Lift and support rear of vehicle. Turn ignition on.
Using DVOM, backprobe ECM connector. Measure voltage between terminal SP1 and ground, while slowly rotating rear wheel. See Figure-7. DVOM should indicate a pulse voltage of 0 to 4.5-5.5 volts.
If voltage is within specification, replace ECM and retest. If voltage is not within specification, inspect for possible open circuit between combination meter and ECM. See wiring diagram in the WIRING DIAGRAMS - 2.7L article. Repair as needed.