Pinpoint Test Q: DTC C1991

Anti-Lock Control - Traction Control and Stability Assist

Pinpoint Test Q: DTC C1991

Normal Operation

The ABS module needs to be calibrated whenever a component specific to the Electronic Stability Control (ESC) or Roll Stability Control (RSC(R)) system is disconnected or a new component is installed. Calibration allows the ABS module to identify the "zero position" of the sensors so the system operates correctly.

- DTC C1991 (Module Calibration Failure)- If the IVD Initialization sequence does not finish or if the ABS module loses the calibration information, DTC C1991 sets.

This pinpoint test is intended to diagnose the following:

- ABS module

- Restraints Control Module (RCM)

- Steering wheel rotation sensor

PINPOINT TEST Q : DTC C1991

NOTE: The stability/traction control indicator "sliding-car icon" flashes when a system calibration is required. Calibration is required after certain DTCs are cleared.

NOTE: The vehicle must be on level ground, at a complete standstill and not on a hoist while carrying out the calibration procedure. Any vehicle movement results in calibration failure.

Q1 CHECK FOR ABS MODULE DTCs

- Connect the scan tool.

- Ignition ON.

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

- Retrieve and record any ABS module DTCs.

Is any other DTC retrieved with C1991?

Yes
DIAGNOSE all other DTCs first. GO to the ABS Module DTC Chart. Anti-Lock Control

Some of the pinpoint tests recommend ABS module calibration prior to any further diagnostics. In this case, GO to Q2.

No
GO to Q2.

Q2 CALIBRATE THE ABS MODULE

- Using the scan tool, carry out the IVD Initialization sequence. Follow the scan tool instructions.

Does the IVD Initialization sequence complete for all of the stability sensors and does the stability/traction control indicator "sliding-car icon" stop flashing and turn off?

Yes
GO to Q3.

No
GO to Q4.

Some concerns cause the calibration not to complete. If sent here from another pinpoint test, return to that pinpoint test for further diagnostics.

Q3 CHECK FOR RETURNING DTCs

- Enter the following diagnostic mode on the scan tool: Self Test- Clear All CMDTCs (Continuous Memory Diagnostic Trouble Codes).

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

- Retrieve and record any ABS module DTCs.

Does the DTC C1991 clear and not return?

Yes
TEST DRIVE the vehicle. REPEAT the self-test.

If sent here from another pinpoint test, return to that pinpoint test for further diagnostics.

No
GO to Q4.

Q4 MONITOR THE STEERING WHEEL ANGLE POSITION (SWA POS) PID

- 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.

Do the PIDs move in intervals of 4.5 degrees?

Yes
The system is operating correctly at this time. The concern may have been caused due to the ABS module not being calibrated or by an incomplete ABS module calibration.

No
GO to Pinpoint Test M. Pinpoint Test M: DTCs B1104, C1277 and C1278