Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. The permanent magnet generator only produces a signal if the drive wheels are turning greater than 5 mph (8 km/h). This step determines if DTC P0502 is the result of a hard failure or an intermittent condition.
3. Proper engine loads cannot be achieved in a shop environment to properly run the vehicle within the Freeze Frame Data conditions. It will be necessary to drive the vehicle on the road to obtain the proper engine loads.
4. This step verifies that the ECM is receiving a signal from the vehicle speed sensor.

1. (8) A resistance reading that is higher than the specified value indicates that the VSS circuitry is open.
2. (10) If the displayed resistance is less than the 1300 ohms, the VSS high and low circuits are shorted together.
3. (11) This checks the resistance of the VSS if no opens or shorts were found on the VSS high and low circuits.
4. (13) The replacement ECM must be reprogrammed.