P0503

SYMPTOM
P0503-VEHICLE SPEED SENSOR 1 ERRATIC

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

SET CONDITION
Vehicle speed signal is erratic during road load conditions. Two Trip Fault for non ETC vehicles and One Trip Fault for ETC vehicles. 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. Scan Tool Testing and Procedures

DIAGNOSTIC TEST
1. ACTIVE DTC





Ignition on, engine not running.

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.

With a scan tool, read DTCs and record the related Freeze Frame data.
Is the DTC active at this time?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5

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.

This code may also set on a hard acceleration on loose gravel or during other off road driving conditions.
Check tire pressure of all the tires.
Check tire wear on all the tires.
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 (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes>> Repair as necessary. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.