With Antilock Brakes

Diagnostic Chart:

Schematic:

Vehicles equipped with a manual transmission with antilock brakes receive vehicle speed from the right front wheel speed sensor. The right front wheel speed sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the right front wheel. The sensor produces a readable AC voltage signal when vehicle speed is above 5 km/h (3 mph). This speed signal is sent to the Electronic Brake and Traction Control Module (EBTCM), which converts the AC voltage of the sensor to a square wave. The square wave is produced by the EBTCM grounding circuit 1909, which is pulled up to 5 volts through a resistor in the PCM. DTC P0502 sets when the PCM does not detect a square wave vehicle speed signal for a certain length of time.

DTC PARAMETERS
DTC P0502 will set if vehicle speed signal is less than 3 km/h (2 mph) when:
^ Condition exists for longer than 5 seconds
^ Engine speed is between 1700 and 3600 rpm
^ MAP is between 24 and 34 kPa
^ TP angle is less than 1%

DTC P0502 diagnostic runs continuously once the above conditions have been met.

P0502 is a type B DTC.

DIAGNOSTIC AIDS

IMPORTANT: If ABS DTC C0040 is also set, diagnose that DTC first. If a right front wheel speed signal is not sent to the EBTCM, the EBTCM will not supply a vehicle speed signal to the PCM.

To locate an intermittent problem, use Scan tool to monitor VEHICLE SPEED with vehicle raised and drive wheels moving greater than 5 km/h (3 mph). Wiggling wires while watching for a change in VEHICLE SPEED may locate the area where an open or short to ground in the wiring could lie.

If no vehicle speed signal is received, the speedometer will be inoperative.