C0253 - Rear Wheel Steering

DTC C0253

Circuit Description
The steering position sensor provides 3 digital signal inputs and 1 analog signal inputs to the rear wheel steering control module. The 3 digital signals are:
^ Phase A
^ Phase B
^ Index pulse
The analog signal is the steering wheel position signal. This is a class 2 signal from the TBC.

The rear wheel position sensor provides 2 discreet analog signal inputs to the rear wheel steering control module. These inputs are:
^ Rear wheel position 1 signal
^ Rear wheel position 2 signal
The rear wheel steering control module compares the differences between the steering wheel position sensor and the rear wheel position sensor. If the difference exceeds the internal values in the rear wheel steering control module than C0253 will set.

Conditions for Running the DTC
^ The ignition is ON.
^ Performing the alignment procedure.

Conditions for Setting the DTC
^ A valid alignment was not performed.
^ The steering wheel sensor analog voltage is out of valid alignment range, which is within 2.0-3.0 volts.
^ The steering wheel sensor marker pulse is out of valid alignment range, and the steering wheel sensor index switch points are not between + or -10° of center.
^ The rear sensor analog voltage out of valid alignment range:
^ The scan tool data parameter rear wheel centering 1 is not within 2.0-3.0 volts.
^ The scan tool data parameter rear wheel centering 2 is not within 2.0-3.0 volts.

Action Taken When the DTC Sets
^ The Service 4 Wheel Steer indicator on IPC will be displayed.
^ The code is displayed on the scan tool as DTC C0253.
^ The output command to the motor is zeroed. The motor drive circuits are disabled using commands to open the power relay, and to close the motor shorting relay.
^ The rear wheels will be returned to the centered position.

Conditions for Clearing the DTC
^ The condition for the DTC is not currently present.
^ The module receives a clear code command from the scan tool.
^ The history DTC clears after 100 malfunction free ignition cycles.
^ A valid alignment is performed.

Diagnostic Aids
^ Inspect for poor connections at the harness connector of the rear wheel steering control module, rear wheel position sensor and the steering wheel position sensor.
^ Observe the rear wheel steering mode select switch. If all of the mode indicator LEDs are illuminated the rear wheel steering control module has lost its memory settings and the scan tool must be used to re-calibrate the rear wheel steering alignment data in the rear wheel steering control module.

Steering Wheel Position Sensor-Digital Signal
^ 3 outputs used (Phase A, Phase B. Index Pulse)
^ Phase A & Phase B
Offset PWM wave forms created when turning the wheel
^ Index pulse
Signal is present only when steering wheel is within 10 degrees either side of center

Steering Wheel Position Sensor-Analog Signal
^ This is a class 2 message from the TBC
^ Voltage is at or near 2.5 volts with wheels at center
^ Voltage increases/decreases for less than one full turn (+/- 225 Degrees), then plateaus for the remainder of the travel





Steering Wheel Position Sensor - Digital Signal





Steering Wheel Position Sensor - Analog Signal

Test Description
The number below refers to the step number on the diagnostic table.
2. This step verifies there was an improper rear wheel steering alignment performed.

Steps 1 - 9:

DTC C0253