P0503

P0503-VEHICLE SPEED SENSOR 1 ERRATIC







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.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Ignition on, engine not running.
2. With a scan tool, select View DTCs and record the related Freeze Frame data.

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.

3. Start the engine.
4. Allow the engine to idle.
5. With a scan tool, select View DTCs.

Is the status Active or Pending for this DTC?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. . Intermittent Condition Test

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.

1. This code may also set on a hard acceleration on loose gravel or during other off road driving conditions.
2. Check tire pressure of all the tires.
3. Check tire wear on all the tires.
4. Ask the customer what the road and driving conditions were like when the fault set.

Were any problems found?

Yes

- Repair as necessary. If the code set during a front OR rear wheel spin condition, no repair is necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3

3. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Wheel Speed Sensors and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Wheel Speed Sensor and the Powertrain Control Module connectors.
4. Search for any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test