P0503

P0503-VEHICLE SPEED SENSOR 1 ERRATIC







Theory of Operation

A vehicle speed frequency signal is hard wired to the Powertrain Control Module (PCM) from the ABS module.

- When Monitored:
Ignition on and battery voltage greater than 11 volts.

- Set Condition:
This code will set if vehicle speed rate of change has exceeded an upper or lower limit a number of times. Two 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.

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 reach normal operating temperature.
5. With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

Is the DTC Active or Pending at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Checking for an Intermittent DTC.

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 air pressure in 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 PCM Verification Test. PCM Verification Test.

No

- Go To 3

3. EXCESSIVE RESISTANCE IN THE (K75) VEHICLE SPEED SIGNAL CIRCUIT




1. Turn the ignition off.
2. Disconnect the ABS Module harness connector.
3. Disconnect the C4 PCM harness connector.
4. Measure the resistance in the (K75) Vehicle Speed Signal circuit from the C4 PCM harness connector to the ABS Module harness connector.

Is the resistance above 5.0 ohms?

Yes

- Repair the excessive resistance in the (K75) Vehicle Speed Signal circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 4

4. EXCESSIVE RESISTANCE IN THE (K75) VEHICLE SPEED SIGNAL CIRCUIT




1. Measure the resistance between ground and the (K75) Vehicle Speed Signal circuit from the C4 PCM harness connector.

Is the resistance below 1000 ohms?

Yes

- Repair the short to ground in the (K75) Vehicle Speed Signal circuit.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 5

5. 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.
4. Verify that there is good pin to terminal contact in the Wheel Speed Sensor and the Powertrain Control Module connectors.
5. Search for any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace and program the Powertrain Control Module.
- Perform the PCM Verification Test. PCM Verification Test.