Pinpoint Test G: DTCs C1278 And C1956
Anti-Lock Control
Pinpoint Tests
Pinpoint Test G: DTCs C1278 and C1956
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number
Normal Operation
The steering wheel rotation sensor (also called the steering wheel angle sensor) monitors the steering wheel position when the slotted-wheel in the sensor passes through the optical field of the sensor.
The ABS module supplies voltage to the rotation sensor along circuit CCA40 (GY/BU). Ground for the sensor is provided by the ABS module along circuit RCA09 (GN/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 will be set.
- DTC C1278 (Steering Wheel Angle 1 and 2 Signal Faulted) - If there is an open, short to ground, short to voltage or high resistance on the steering wheel angle sensor power or ground circuits, DTC C1278 will set.
- DTC C1956 (Steering Angle Sensor Circuit Failure) - If the ABS module detects an open, a short to ground or a short to voltage on circuit VCS06 (GY/BN) or VCS07 (VT/OG), DTC C1956 will be set.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Steering wheel rotation sensor
PINPOINT TEST G: DTCs C1278 AND C1956
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
NOTICE: Overtightening of the steering wheel rotation sensor fasteners may deform or damage the sensor housing, possibly resulting in improper 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.
-------------------------------------------------
G1 CHECK FOR VOLTAGE AT THE STEERING WHEEL ROTATION SENSOR
- Ignition OFF.
- Disconnect: Steering Wheel Rotation Sensor C222 .
- Ignition ON.
- Measure the voltage between steering wheel rotation sensor C222-4, circuit CCA40 (GY/BU), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to G2.
No
REPAIR circuit CCA40 (GY/BU). CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
G2 CHECK THE STEERING WHEEL ROTATION SENSOR GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: ABS Module C135 .
- Measure the resistance between steering wheel rotation sensor C222-1, circuit RCA09 (GN/VT), harness side and ABS module C135-12, circuit RCA09 (GN/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to G3.
No
REPAIR circuit RCA09 (GN/VT). CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
G3 CHECK THE STEERING WHEEL ROTATION SENSOR SIGNAL CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between ground and:
- steering wheel rotation sensor C222-3, circuit VCS07 (VT/OG), harness side.
- steering wheel rotation sensor C222-2, circuit VCS06 (GY/BN), harness side.
- Is any voltage present?
Yes
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
No
GO to G4.
-------------------------------------------------
G4 CHECK THE STEERING WHEEL ROTATION SENSOR SIGNAL CIRCUITS FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between ground and:
- steering wheel rotation sensor C222-3, circuit VCS07 (VT/OG), harness side.
- steering wheel rotation sensor C222-2, circuit VCS06 (GY/BN), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to G5.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
G5 CHECK THE STEERING WHEEL ROTATION SENSOR SIGNAL CIRCUITS FOR AN OPEN
- Measure resistance between the steering wheel rotation sensor C222, harness side and ABS module C135, harness side using the following chart:
- Is the resistance less than 5 ohms?
Yes
GO to G6.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------
G6 CHECK THE STEERING WHEEL ROTATION SENSOR SIGNAL CIRCUITS FOR A SHORT TOGETHER
- Measure the resistance between steering wheel rotation sensor C222-3, VCS07 (VT/OG), harness side and steering wheel rotation sensor C222-2, circuit VCS06 (GY/BN), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
INSTALL a new steering wheel rotation sensor. REFER to Steering Wheel Rotation Sensor Service and Repair. CARRY OUT the self test with the brake pedal not applied.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
-------------------------------------------------