DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input
The vehicle speed sensor (VSS) is a permanent magnet (PM) generator attached to the transmission case. The final drive assembly has a toothed wheel (VSS rotor). As the final drive assembly rotates, an AC voltage is induced and transmitted to the PCM. The PCM converts the AC voltage into a digital signal. The PCM uses the vehicle speed in order to determine shift timing, torque converter clutch (TCC) apply and release, and gear ratio. The VSS voltage will vary from 0.5 volts AC at 100 RPM to more than 100 volts AC at 8000 RPM. The VSS resistance value is 1300-1950 ohms.
If the PCM detects a low vehicle speed and a high input shaft speed sensor signal while in a drive range, then DTC P0502 sets. DTC P0502 is a type B DTC.
Conditions for Running the DTC
" No TP DTCs P0121, P0122 or P0123.
" No VSS DTC P0503.
" No AT ISS DTCs P0716 or P0717.
" No IMS DTCs P1820, P1822, P1823, or P1825.
" The system voltage is 8-18 volts.
" The engine run time is greater than 5 seconds.
" The engine is not in fuel cut off.
" The transmission is not in PARK or NEUTRAL.
" The TP angle is greater than 12%.
" The engine torque is 60-395 N m (44-291 lb ft).
" The input shaft speed is 1000-5000 RPM.
Conditions for Setting the DTC
The output speed is less than 372 RPM for 3 seconds.
Action Taken When the DTC Sets
" The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
" The PCM commands maximum line pressure.
" The PCM freezes transmission adapt functions.
" The PCM calculates vehicle speed from the automatic transmission input (shaft) speed sensor and commanded gear.
" The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
" The PCM stores DTC P0502 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
The vehicle speed sensor is located on the RH transmission extension housing, near the rh axle shaft.
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Thursday, April 1st, 2010 AT 12:29 AM