C1003-86

C1003-86-VEHICLE SPEED SIGNAL INVALID

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Electronic Power Steering (EPS) system employs a column-mounted electric power steering unit along with a manual steering rack and pinion to provide a variable power-assisted steering with reduced parasitic engine load. The EPS controller monitors two steering wheel position sensors to determine the absolute position of the steering shaft and determines driver input via a steering wheel torque sensor. In addition, the EPS controller uses four hall-effect position sensors to monitor the absolute and commanded position of the motor. The EPS controller obtains vehicle speed, alternator output, and steering mode information, and broadcasts warning lamp status and service diagnostic information, on CAN C. During normal driving, as the driver turns the wheel, the torque sensor value changes based on the effort the driver uses to turn the wheel. The controller uses this information, along with the steering wheel absolute position and vehicle speed, to determine the amount torque required from the motor. Voltage is then provided to the motor to provide power steering assist.

- When Monitored:
Continuously.

- Set Condition:
The EPS Module received an invalid vehicle speed message from the Anti-Lock Brakes Module (ABS) Module for 2.5 seconds.





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

1. VERIFY DTC IS ACTIVE

NOTE: Diagnose all CAN C communication failures before continuing.

1. Ignition on, engine not running.
2. Using a scan tool, read EPS DTCs.

Is the DTC active at this time?

Yes

- Go To 2

No

- The conditions that caused this code to set are not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors, pay particular attention the CAN circuits.
- Perform the EPS Verification Test. EPS Verification Test.

2. VERIFY ABS MODULE IS ACTIVE ON CAN C BUS
1. Using a scan tool, select ECU View.
2. Verify that the ABS Module is active on the bus.

Is the ABS Module active on the bus?

Yes

- Go To 3

No

- Perform the appropriate diagnostic procedure Testing and Inspection.

3. CHECK FOR ACTIVE OR STORED DTCs IN ABS MODULE
1. Using a scan tool, read ABS Module DTCs.

Are any DTCs active or stored in the ABS Module?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 4

4. CHECK FOR ACTIVE OR STORED COMMUNICATION DTCs IN BCM
1. Using a scan tool, read BCM DTCs.

Are any active of stored ABS Module Communication DTCs set in the BCM?

Yes

- Perform the appropriate diagnostic procedure Testing and Inspection.

No

- Replace the Electronic Power Steering (EPS) Assembly. Steering Column - Removal.
- Perform the EPS Verification Test. EPS Verification Test.