C0508

CIRCUIT DESCRIPTION
The Power Steering Control Module (PSCM) supplies a 5.0 volt reference and a ground circuit to the Steering Wheel Position (SWP) Sensor. The SWP sensor returns a voltage signal to the PSCM indicating the steering wheel rate of steer. The SWP Sensor returns a voltage between 0.2 - 4.9 volts when the steering wheel has been turned one quarter revolution (90 degrees). The PSCM monitors the SWP sensor signal voltage to control a pulse width modulation cur-rent (percentage DUTY CYCLE) to the power steering fluid flow actuator.

CONDITIONS FOR SETTING THE DTC
The SWP Sensor signal circuit voltage is greater than 4.9 volts for one second or longer.

ACTION TAKEN WHEN THE DTC SETS
The PSCM will not send any current to the power steering fluid flow actuator. This will result in the power steering fluid flow actuator valve to retract providing maximum fluid flow and full power steering assist at all times.

CONDITIONS FOR CLEARING THE MIL/DTC
1. A history DTC will clear after 100 concurrent ignition cycles has occurred without the fault reoccur-ring.
2. The history and current DTC(s) can be cleared using the Tech 2 scan tool.

DIAGNOSTIC AIDS
The Tech 2 scan tool will read steering wheel position in volts. With the ignition switch in the "ON" position and as the steering wheel position sensor is rotated, the voltage reading should be between 0.2 - 4.9 volts. Voltage should increase at a steady rate up to 4.9 volts when the wheel is turned, one quarter revolution (90 degrees) in either direction.
- Above 0.2 volts.
- Below 4.9 volts when the steering wheel is rotated one quarter revolution (90 degrees).
Using the Tech 2, scan the SWP Sensor.
- Above 0.2 volts.
- Turn the steering wheel.
- The Tech 2 display should increase from above 0.2 volts and below 4.9 volts as the steering wheel is turned one quarter revolution (90 degrees).


TEST DESCRIPTION
The Step numbers below refer to the same step numbers in the Steering Wheel Position Sensor - Signal Voltage High Diagnostic Table
- Step 1 check prompts the technician to complete some basic checks and store the Freeze Frame Data. This also allows the technicians to stored failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This stored information in the scan tool can be referred to later.
- Step 2 verifies When the voltage is between 0.2 and 4.9 volts, the PSCM will use this voltage to detect changes in the rate of steering and the system voltage should increase and decrease proportional to steering wheel rotation. If the voltage is not within specifications an appropriate DTC will set. In addition to DTC diagnosis, check for binding, grinding or damaged steering wheel position sensor.
- Step 5 probes the ground circuit checks the circuit for high resistance which will cause a DTC G0508 to set.
- Step 6 verifies a shorted 5.0 volt reference circuit may also set additional DTC's.
- Step 11 verifies before replacing the PSCM, check terminals for improper mating, broken locks and physical damage to the wiring harness.