C1278
Anti-Lock Control - Non-Hybrid
Pinpoint Test F: DTCs C1277, C1278 and C1963
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. [1][2]Diagrams By Number
Normal Operation
On vehicles equipped with Hydraulic Power Assist Steering (HPAS) (3.5L vehicles only), a slotted wheel is attached to the steering column inside the clockspring and the steering wheel rotation sensor is attached to the RH side of the multifunction switch just above the ignition lock cylinder. The steering wheel rotation senor has a LED and an opposing optical sensor. As the steering wheel is turned, the slotted wheel passes between the LED and the sensor, interrupting the signal and indicating how far and how fast the steering wheel is being turned. This information is sent to the ABS module and is used to help determine if the AdvanceTrac(R) system needs to be activated.
On vehicles equipped with Electronic Power Assist Steering (EPAS) , the steering wheel rotation sensor is located inside the EPAS (Electronic Power Assist Steering) gear assembly. Rotation speed and angle are sent to the ABS module from the Power Steering Control Module (PSCM) along the High Speed Controller Area Network (HS-CAN) bus.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Steering wheel rotation sensor incorrectly installed
- Steering wheel rotation sensor
- ABS module
PINPOINT TEST F : DTCs C1277, C1278 AND C1963
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
F1 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 F4.
No
GO to F2.
F2 CHECK THE ABS MODULE DTCs
- Review the DTCs retrieved during Inspection and Verification.
Are there any communication "U-code" DTCs present in the ABS module?
Yes
REFER to the ABS Module DTC Chart and DIAGNOSE the U-code DTCs before diagnosing DTC C1963. ABS Module DTC Chart
No
GO to F3.
F3 CHECK FOR PSCM (Power Steering Control Module) DTCs
- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self Test- PSCM (Power Steering Control Module).
Are there any DTCs present in the PSCM (Power Steering Control Module)?
Yes
REFER to Steering to diagnose the EPAS (Electronic Power Assist Steering) system concern.
No
GO to Pinpoint Test G. Pinpoint Test G: DTCs C1963, C2777, U0151, U0452 and U1901
F4 MONITOR THE STEERING ROTATION SENSOR POSITION (SWA POS) PID
- Connect the scan tool.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger- ABS Module.
- Monitor the SWA POS PID while rotating the steering wheel clockwise and counterclockwise very slowly, from lock to lock.
Does the PID move in intervals of 1.5 degrees?
Yes
CLEAR the DTCs. DRIVE the vehicle above 48 km/h (30 mph) with input from the steering wheel rotation sensor. RETRIEVE the DTCs. If DTC C1277 or C1278 is still present, GO to F13.
If DTC C1963 is present, INSPECT the steering wheel rotation sensor for damage and correct installation. INSPECT for possible sources of light intrusion (cracked, missing or poor fitting steering shroud). REINSTALL or INSTALL new as necessary. If the sensor is OK, GO to F5.
No
GO to F5.
F5 CHECK THE VOLTAGE TO THE STEERING WHEEL ROTATION SENSOR
NOTE: The steering wheel rotation sensor is located on the RH side of the multifunction switch.
- Ignition OFF.
- Disconnect: Steering Wheel Rotation Sensor C226.
- Ignition ON.
- Measure the voltage between steering wheel rotation sensor C226-4, circuit CCA40 (GY/BU), harness side and ground.
Is the voltage greater than 9.5 volts?
Yes
GO to F6.
No
REPAIR circuit CCA40 (GY/BU). CLEAR the DTCs. REPEAT the self-test.
F6 CHECK THE GROUND CIRCUIT FOR AN OPEN
- Measure the voltage between steering wheel rotation sensor C226-4, circuit CCA40 (GY/BU), harness side and steering wheel rotation sensor C226-1, circuit RCA40 (BN/VT), harness side.
Is the voltage greater than 9.5 volts?
Yes
GO to F7.
No
REPAIR circuit RCA40 (BN/VT). CLEAR the DTCs. REPEAT the self-test.
F7 CHECK THE CHANNEL "A" CIRCUIT FOR AN OPEN OR A SHORT TO GROUND
- Measure the voltage between steering wheel rotation sensor C226-2, circuit VCA41 (VT/GN), harness side and steering wheel rotation sensor C226-1, circuit RCA40 (BN/VT), harness side.
Is the voltage between 4.75 volts and 5.25 volts?
Yes
GO to F8.
No
REPAIR circuit VCA41 (VT/GN). CLEAR the DTCs. REPEAT the self-test.
F8 CHECK THE CHANNEL "B" CIRCUIT FOR AN OPEN OR A SHORT TO GROUND
- Measure the voltage between steering wheel rotation sensor C226-3, circuit VCA42 (VT/OG), harness side and steering wheel rotation sensor C226-1, circuit RCA40 (BN/VT), harness side.
Is the voltage between 4.75 volts and 5.25 volts?
Yes
GO to F9.
No
REPAIR circuit VCA42 (VT/OG). CLEAR the DTCs. REPEAT the self-test.
F9 CHECK THE STEERING POSITION SENSOR CIRCUITS FOR AN OPEN
NOTE: The degas bottle may need to be positioned aside to access the ABS module connector.
- Ignition OFF.
- Disconnect: ABS Module C135.
- Disconnect: Steering Wheel Rotation Sensor C226.
- Measure the resistance between ABS module C135, harness side and steering wheel rotation sensor C226, harness side using the following table:
Steering Wheel Rotation Sensor Circuit ABS Module C226-1 RCA40 (BN/VT) C135-40 C226-2 VCA41 (VT/GN) C135-41 C226-3 VCA42 (VT/OG) C135-9 C226-4 CCA40 (GY/BU) C135-5
Are the resistances less than 5 ohms?
Yes
GO to F10.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
F10 CHECK THE STEERING POSITION SENSOR CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between:
- ABS module C135-5, circuit CCA40 (GY/BU), harness side and ground.
- ABS module C135-9, circuit VCA42 (VT/OG), harness side and ground.
- ABS module C135-40, circuit RCA40 (BN/VT), harness side and ground.
- ABS module C135-41, circuit VCA41 (VT/GN), harness side and ground.
Is any voltage present?
Yes
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
No
GO to F11.
F11 CHECK THE STEERING POSITION SENSOR CIRCUITS FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between:
- ABS module C135-5, circuit CCA40 (GY/BU), harness side and ground.
- ABS module C135-9, circuit VCA42 (VT/OG), harness side and ground.
- ABS module C135-40, circuit RCA40 (BN/VT), harness side and ground.
- ABS module C135-41, circuit VCA41 (VT/GN), harness side and ground.
Are the resistances greater than 10,000 ohms?
Yes
GO to F12.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
F12 CHECK THE CHANNEL "A" AND "B" CIRCUITS FOR A SHORT TOGETHER
- Measure the resistance between steering wheel rotation sensor C226-2, circuit VCA41 (VT/GN), harness side and steering wheel rotation sensor C226-3, circuit VCA42 (VT/OG), harness side.
Are the resistances greater than 10,000 ohms?
Yes
If DTC C1963 is present, GO to Pinpoint Test G. Pinpoint Test G: DTCs C1963, C2777, U0151, U0452 and U1901
INSTALL a new steering wheel rotation sensor. REFER to Steering Wheel Rotation Sensor . CLEAR the DTCs. REPEAT the self-test.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
F13 CHECK FOR CORRECT ABS MODULE OPERATION
- Ignition OFF.
- Disconnect: ABS Module C135.
- Check the connector for:
- corrosion.
- pushed-out pins.
- spread terminals.
- Connect: ABS Module C135.
- Make sure the connector seats correctly, then operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module . TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.