Transmission Controls Diagnosis

Diagnostic Chart:

Schematic:

The output speed sensor (OSS) produces an AC voltage of different amplitude and frequency depending on the velocity of the output shaft. The OSS produces the signal from 16 evenly spaced machined notches on the transaxle final drive assembly. The OSS produces a readable AC voltage signal when vehicle speed is above 5 km/h (3 mph). This OSS signal is sent to the PCM, which is used to determine vehicle speed. DTC P0502 sets when the PCM does not detect an OSS signal for a certain length of time.

DTC PARAMETERS
DTC P0502 will set if OSS signal is less than 100 rpm when:
^ Condition exists for longer than 3 seconds
^ Transaxle is not is Park/Neutral
^ Input speed is greater than 2000 rpm
^ MAP is greater than 50 kPa
^ TP angle is greater than 12%
^ No ISS, MAP, TP or P1810 DTCs have been set.

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

P0502 is a type B DTC.

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

If no OSS signal is received, the speedometer will be inoperative. Once P0502 is set, the speedometer will be inoperative for the rest of the ignition cycle even if a valid signal is later received.

If the PCM does not receive an OSS signal, it will command maximum main line pressure to the transaxle. Shift timing will be affected as well.

OSS resistance: 1530 - 1870 ohms