P0503-VEHICLE SPEED SENSOR 1 ERRATIC
For a complete wiring diagram, refer to the Wiring Information.
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.
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When Monitored:
Ignition on and battery voltage greater than 10 volts. Transmission in Drive or Reverse.
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Set Condition:
This code will set if no vehicle speed signal is received from the ABS Module for up to 120 seconds for 2 consecutive trips. One Trip Fault. Three good trips to turn off the MIL.
Possible Causes |
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| ACTIVE BUS OR COMMUNICATION DTCS |
| TIRE CIRCUMFERENCE |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
| 1. | 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. |
| 2. | With a scan tool, select View DTCs and record the related Freeze Frame data. |
Is the DTC Active at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
| 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. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
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 Vehicle Speed Sensors, ABS Module, 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 Vehicle Speed Sensors, ABS Module, and Powertrain Control Module connectors. |
| 4. | Perform any Technical Service Bulletins that may apply. |
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).