Test Procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis

-- Connect the scan tool.

-- Perform a road test with a vehicle speed greater than 5 Km/h.

-- Using the scan tool, Check the vehicle speed:

-- Compare the vehicle speed on the scan tool to the Speedometer -G21-.

Specified value: a difference of no greater than 10%.

If the specified value was not obtained or no speed was displayed on the cluster:

-- Check the wiring from the Engine Control Module (ECM) -J623- to the Instrument Cluster Control Module -J285- for high resistance, an open circuit, Short to Battery positive or to Ground.

-- Check the wiring connection for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection. Vehicles without a Vehicle Speed Sensor on the transmission will get a bussed signal from the ABS module. If ECM and Cluster have no speed displayed, check the ABS module for a wheel speed sensor or communication fault.