Test Procedure

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

Function test

-- Connect the scan tool.

-- Perform a road test with a vehicle speed greater than 25 MPH.

-- 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:

-- Check the wiring from the Engine Control Module (ECM) -J623- electrical harness connector to the Instrument Cluster Control Module -J285- for an open circuit, Short to Battery (+), or to Ground. Refer to Wiring Diagram.

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

-- If necessary, repair the faulty wiring connection.