Circuit Description
The EBTCM uses four inputs from the Steering Wheel Position sensor:
| • | Phase A digital input |
| • | Phase B digital input |
| • | Index pulse |
| • | Analog input |
This information is used to calculate three things:
- The front wheels position when centered.
- The front wheels position when turning.
- The rate at which the steering wheel is turning.
The EBTCM runs a centering routine when the vehicle speed goes above 30 Km/h (18 mph). When the vehicle reaches 30 Km/h (18 mph), the EBTCM monitors the Steering Wheel Position Sensor inputs (Phase A, Phase B and Analog voltage) to see if the steering wheel is moving. If the steering wheel is not moving for a set period of time then the EBTCM assumes the vehicle is going in a straight line. At this point, the EBTCM looks at the analog voltage signal and reads the voltage. This voltage normally around 2.5V, is then considered the center position and the digital degrees also become zero at the same time. This centering routine is necessary to compensate for wear in the steering and suspension. Wear in the steering and suspension can result in a change in the relationship between the steering wheel and the front tires when driving in a straight line. By running the centering routine the EBTCM can compensate for these changes by changing the digital and analog center position.
The EBTCM uses the digital input (Phase A and Phase B) from the Steering Wheel Position Sensor to calculate the direction the driver of the vehicle is trying to steer during an ABS event. This information is also used to calculate the rate at which the steering wheel is turning to control the amount of effort required from the driver to turn the steering wheel using Magna Steer®.
Conditions for Setting the DTC
| • | DTC C1287 can be set any time ignition is present. A fault exists if the steer rate (speed that the steering wheel appears to be turning) exceeds the limits set by the EBTCM. |
Action Taken When the DTC Sets
| • | Magna Steer® is disabled ABS/TCS remains active. |
Conditions for Clearing the DTC
| • | Condition for DTC is no longer present and scan tool clear DTC function is used. |
| • | Fifty ignition cycles have passed with no DTC(s) detected. |
Diagnostic Aids
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Checks for normal state change of phase A and Phase B when turning left.
-
Checks for normal state change of phase A and Phase B when turning right.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
Did phase A and phase B change states uniformly as the steering wheel was rotated? | -- | |||
Slowly rotate the steering wheel to the right while monitoring phase A and phase B of the Steering Wheel Position Sensor using a scan tool. Did phase A and phase B change states uniformly as the steering wheel was rotated? | -- | |||
4 | Replace the Steering Wheel Position Sensor. Refer to Steering Wheel Position Sensor Replacement in Steering Wheel and Column in. Is the replacement complete? | -- | -- | |
5 |
Did DTC C1287 set as a current DTC? | -- | Go to Diagnostic System Check | |
6 | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module . Is the replacement complete? | -- | Go to Diagnostic System Check | -- |
