Minivek:
Let’s Fix Something
This 2002 Lincoln LS had the message “Check Advance Trac” displayed on the odometer as well as a flashing traction control light. The fault code retrieved from the ABS module was a C1277 — Steering Wheel Angle Offset Failure (See LS1).
The ABS module knows that while driving (VSS signal), the steering wheel should average around its physical center. If the steering wheel’s sensor is averaging more than 15 calculated degrees from center, then something must be wrong because it is not logical for the vehicle to be in a constant steer at highway speeds for long distances (not made for dirt track racers!).
Pulling up the steering angle sensor’s PID, with the steering wheel at a physical center shows the calculated angle is not within 15 degrees of physical center. In fact, it is at negative 302 degrees, or 302 degrees to the left (See LS2).
Inspection of the sensor found nothing wrong. It is possible that the steering wheel had been moved with the ABS module powered down… like from a dead battery maybe, or the key just barely turned enough to unlock the steering wheel and not power up the module. The steering angle needed to be retrained. To do this, an IVD initialization sequence needed to be performed. This is when the yaw rate sensor and the steering angle sensor are re-centered.
After accessing the steering angle sensor recalibration test (See IVD initialization 1 and 2), the tool instructs the technician to not bounce the vehicle and for him to rotate the steering wheel from lock to lock. When retraining the yaw rate and lateral accelerometer, is important to have the vehicle on level ground with no extra weight inside the vehicle… including the technician, so it will be necessary to reach in through an open window to operate the steering wheel. After retraining the steering wheel sensor’s center, the fault code is cleared and ready to return the vehicle to the customer. Anytime one of the following fault codes are cleared:
* C1277 Steering Wheel Angle 1 and 2 Circuit Failure (Some years and models may list this as “Offset failure”)
* C1278 Steering Wheel Angle 1 and 2 Signal Fault
* C1279 Yaw Rate Sensor Circuit Failure
* C1280 Yaw Rate Sensor Signal Fault
* C1281 Lateral Accelerometer Circuit Failure
* C1282 Lateral Accelerometer Signal Fault
* C1285 Booster Solenoid Circuit Failure
* C1287 Booster Pedal Force Switch Circuit Failure
* C1288 Brake Pressure Transducer Input Circuit Failure
* C1440 Pressure Transducer Input Signal Failure
* C1516 Roll Rate Signal Fault
* C1517 Roll Rate Sensor Circuit Fault
* C1730 Reference Voltage Out of Range (+5 V)
* C1991 Module Calibration Failure
* C1996 Active Yaw Control Disabled
* C2769 Longitudinal Acceleration Sensor Circuit Failure
* C2770 Longitudinal Acceleration Sensor Signal Fault
* C2777 Sensor Cluster Bus Failure
* C2778 Sensor Cluster Power Supply Failure
The IVD initialization sequence will have to be performed. The ABS module is programmed to know the difference between clearing one of the above codes, and when you are clearing any other code that might be stored in the ABS module. When one of these codes is cleared, it is replaced with a C1998 for “Module Calibration error.” As seen in the screen shot labeled “Calibration Failure.”
A C1998 is a code that does illuminate the Advance Trac light and will display “Check advance trac” on the message center. Let’s say a customer comes into your shop with an Advance Trac light on with a “check Advance Trac” message on the display. Your tech pulls a fault code C1440. This may be a simple, straight forward pressure transducer replacement. The job itself is very easy. However, when the tech clears the code, a C1998 replaces it and the light and warning message still remain.
If you do not have a scan tool capable of performing an IVD initialization process, like the OE Ford tool, then you will have to outsource the job. As you know, this can be a sticky situation to be in. To answer this need, you’ll find that alternative scan tool makers are stepping up and adding this function to their tool (See IVD on AE).
Make sure your scanner will perform this function before you attempt to repair one of these systems. I hope you have enjoyed the information and have the opportunity to profit from it soon.
