C1278

Anti-Lock Control

Pinpoint Test H: DTCs C1278, C1956, C1963 and C1975

Normal Operation

The steering wheel rotation sensor on vehicles equipped with Hydraulic Power Assist Steering (HPAS) measures the rate of rotation of the steering wheel by monitoring a slotted-wheel as it passes through the sensor gap. This information is sent directly to the ABS module. The ABS module uses this information for AdvanceTrac(R) system operation. The ABS module also compares this information to information it receives from other sensors (brake pedal input, Restraints Control Module (RCM), etc.) to determine how valid the information is and to determine if an instability event is about to occur.

Fused ignition voltage is supplied to the rotation sensor from Smart Junction Box (SJB) fuse 35 (10A) along circuit CBP35 (YE/GY). Ground for the sensor is provided by the ABS module along circuit RCS06 (BN/VT). The steering wheel rotation sensor sends information to the ABS module along circuits VCS06 (GY/BN) and VCS07 (VT/OG). If the ground or power to the steering wheel rotation sensor is interrupted, DTC C1278 sets.

On vehicles equipped with Electronic Power Assist Steering (EPAS), the Power Steering Control Module (PSCM) sends the steering wheel position information over the High Speed Controller Area Network (HS-CAN) bus. Vehicles with EPAS (Electronic Power Assist Steering) have a Steering Angle Sensor Module (SASM) installed behind the clockspring. If the vehicle is equipped with Active Park Assist (identified by the presence of the Active Park Assist button on the center console), the SASM (Steering Angle Sensor Module) is fully functional and broadcasts steering angle information over the HS-CAN (High Speed Controller Area Network) bus.





This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- Steering wheel rotation sensor

- EPAS (Electronic Power Assist Steering) steering gear (if equipped)

- SASM (Steering Angle Sensor Module) (if equipped)

PINPOINT TEST H : DTCs C1278, C1956, C1963 AND C1975

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTICE: Overtightening of the steering wheel rotation sensor fasteners may deform or damage the sensor housing, possibly resulting in faulty operation.

NOTE: Make sure that the steering wheel rotation sensor is mounted securely to the column with 2 fasteners. A loose sensor or missing fastener may result in incorrect sensor operation. Make sure that the sensor connector is mated securely to the harness connector. Before proceeding with electrical testing, make sure that the vehicle battery is fully charged.

H1 CHECK THE ABS MODULE DTCs

- Review the ABS module DTCs retrieved while carrying out the steps in Inspection and Verification.

Is DTC C1963 and/or C1975 present?

Yes
GO to H2.

No
GO to H6.

H2 VERIFY THE VEHICLE STEERING SYSTEM TYPE

NOTE: Steering system type can be identified by checking for the presence of a power steering pump. Vehicles equipped with EPAS (Electronic Power Assist Steering) do not have a power steering pump.

- Verify the type of steering system the vehicle is equipped with, HPAS (Hydraulic Power Assist Steering) or EPAS (Electronic Power Assist Steering).

Is the vehicle equipped with HPAS (Hydraulic Power Assist Steering)?

Yes
GO to H6.

No
GO to H3.

H3 VERIFY THE VEHICLE IS EQUIPPED WITH ACTIVE PARK ASSIST

- Verify that the vehicle is equipped with Active Park Assist by checking for the presence of the Active Park Assist button on the center console.

Is the vehicle equipped with Active Park Assist?

Yes
GO to H4.

No
GO to H5.

H4 CHECK FOR SASM (Steering Angle Sensor Module) DTCs

- Connect the scan tool.

- Enter the following diagnostic mode on the scan tool: Self Test- SASM (Steering Angle Sensor Module).

- Retrieve and record any SASM (Steering Angle Sensor Module) DTCs.

Are any SASM (Steering Angle Sensor Module) DTCs present?

Yes
GO to the Steering Angle Sensor Module (SASM) DTC Chart. Antilock Brakes / Traction Control Systems

No
GO to H5.

H5 CHECK FOR PSCM (Power Steering Control Module) DTCs

- Connect the scan tool.

- Enter the following diagnostic mode on the scan tool: Self Test- PSCM (Power Steering Control Module).

- Retrieve and record any PSCM (Power Steering Control Module) DTCs.

Are any PSCM (Power Steering Control Module) DTCs present?

Yes
GO to Steering System to diagnose the PSCM (Power Steering Control Module). Antilock Brakes / Traction Control Systems

No
GO to Pinpoint Test I. Pinpoint Test I: DTCs C1280, C1282, C1963, C1975, U0074, U0151, and U0452

H6 MONITOR THE STEERING WHEEL ANGLE (SWA) PID

- Connect the scan tool.

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: DataLogger- ABS.

- Monitor the SWA PID while rotating the steering wheel clockwise and counterclockwise very slowly, from lock to lock.

Do the PIDs change in intervals of 1 degree and show a 360 degree increase for each complete revolution of the steering wheel?

Yes
GO to H7.

No
GO to H8.

H7 CHECK FOR RETURNING DTCs

- Clear the ABS module DTCs.

- Drive the vehicle above 48 km/h (30 mph) with input from the steering wheel.

- Enter the following diagnostic mode on the scan tool: Self Test- ABS Module.

- Retrieve and record any ABS module DTCs.

Are any ABS module DTCs present?

Yes
If DTCs C1277, C1278, C1963 or C1975 are present, GO to H8.

For all other DTCs, GO to the ABS Module DTC Chart. Antilock Brakes / Traction Control Systems

No
The condition is not present at this time. INSPECT the rotation sensor and the slotted-wheel for cracks, looseness and foreign material. REPAIR or INSTALL new as necessary. CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test. If DTCs C1963 and/or C1975 return, GO to Pinpoint Test I. Pinpoint Test I: DTCs C1280, C1282, C1963, C1975, U0074, U0151, and U0452

H8 CHECK THE STEERING WHEEL ROTATION SENSOR CONDITION AND INSTALLATION

- Inspect the steering wheel rotation sensor and slotted-wheel for damage and correct installation. Refer to Steering Wheel Rotation Sensor .

Are the sensor and toothed-wheel installed correctly and undamaged?

Yes
GO to H9.

No
REINSTALL or INSTALL new as necessary. CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test. If DTCs C1963 and/or C1975 return, GO to Pinpoint Test I. Pinpoint Test I: DTCs C1280, C1282, C1963, C1975, U0074, U0151, and U0452

H9 CHECK FOR VOLTAGE AT THE STEERING WHEEL ROTATION SENSOR

- Ignition OFF.

- Disconnect: Steering Wheel Rotation Sensor C226.

- Ignition ON.

- Measure the voltage between steering wheel rotation sensor C226-4, circuit CBP35 (YE/GY), harness side and ground.





Is the voltage greater than 10 volts?

Yes
GO to H10.

No
VERIFY SJB (Smart Junction Box) fuse 35 (10A) is OK. If OK, REPAIR circuit CBP35 (YE/GY).

If not OK, Refer to the Wiring Diagrams to identify possible causes of the circuit short. CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test. Electrical Diagrams

H10 CHECK THE SENSOR RETURN CIRCUIT FOR AN OPEN

- Ignition OFF.

- Disconnect: ABS Module C135.

- Measure the resistance between steering wheel rotation sensor C226-1, circuit RCS06 (BN/VT), harness side and ABS module C135-12, circuit RCS06 (BN/VT), harness side.





Is the resistance less than 5 ohms?

Yes
GO to H11.

No
REPAIR circuit RCS06 (BN/VT). CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.

H11 CHECK THE SENSOR SIGNAL CIRCUITS FOR A SHORT TO VOLTAGE

- Ignition ON.

- Measure the voltage between ground and:
- steering wheel rotation sensor C226-3, circuit VCS07 (VT/OG), harness side.

- steering wheel rotation sensor C226-2, circuit VCS06 (GY/BN), harness side.






Is any voltage present?

Yes
REPAIR the affected circuit(s). CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.

No
GO to H12.

H12 CHECK THE SENSOR SIGNAL CIRCUITS FOR A SHORT TO GROUND

- Ignition OFF.

- Measure the resistance between ground and:
- steering wheel rotation sensor C226-3, circuit VCS07 (VT/OG), harness side.

- steering wheel rotation sensor C226-2, circuit VCS06 (GY/BN), harness side.






Are the resistances greater than 10,000 ohms?

Yes
GO to H13.

No
REPAIR the affected circuit(s). CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.

H13 CHECK THE SENSOR SIGNAL CIRCUITS FOR AN OPEN

- Measure resistance between the steering wheel rotation sensor C226, harness side and ABS module C135, harness side using the following chart:

Steering Wheel Rotation Sensor Circuit ABS Module C226-3 VCS07 (VT/OG) C135-29 C226-2 VCS06 (GY/BN) C135-8






Is the resistance less than 5 ohms?

Yes
GO to H14.

No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.

H14 CHECK THE SENSOR SIGNAL CIRCUITS FOR A SHORT TOGETHER

- Measure the resistance between steering wheel rotation sensor C226-3, VCS07 (VT/OG), harness side and steering wheel rotation sensor C226-2, circuit VCS06 (GY/BN), harness side.





Is the resistance greater than 10,000 ohms?

Yes
If sent here because DTC C1963 and/or C1975 are present, GO to Pinpoint Test I. Pinpoint Test I: DTCs C1280, C1282, C1963, C1975, U0074, U0151, and U0452

For all other instances, INSTALL a new steering wheel rotation sensor. REFER to Steering Wheel Rotation Sensor . CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.

No
REPAIR the affected circuit(s). CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.