P0503-VEHICLE SPEED SENSOR 1 ERRATIC





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The vehicle speed sensor rationality is a continuous test that monitors the vehicle speed sensor for lack of activity. The rationality will not run if a limp-in exists for MAP, Throttle Position, and Engine Coolant Temperature. If vehicle speed sensor is below a minimum threshold for a period of time after the vehicle is operated at a sufficient load, a failure will be indicated.

  • When Monitored:

    Ignition on and battery voltage greater than 10 volts. Transmission in Drive or Reverse.

  • Set Condition:

    This code will set if no vehicle speed signal is received from the ABS Module up to 120 seconds for 2 consecutive trips. One Trip Fault. Three good trips to turn off the MIL.


Possible Causes
  
ACTIVE BUS OR COMMUNICATION DTCS
  
TIRE CIRCUMFERENCE
  
PCM
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1.ACTIVE DTC


NOTE: Check for any Bus Communication DTCs. If no Bus or Communication DTCs are set, check for active DTCs stored in the Anti-Lock Brake Module. Any bus or communication DTCs or VSS DTCs in the Anti-Lock Brake Module must be properly diagnosed before continuing.




Is the DTC Active at this time?

Yes
  • Go To 2


No

2.VISUAL INSPECTION

NOTE: This code can set due to tire circumference differences and from the front or rear wheels being on a slippery surface while the opposite tires are not.







Were any problems found?

Yes


No
  • Go To 3

3.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.




Were there any problems found?

Yes


No