C0472

CIRCUIT DESCRIPTION
The Electronic Variable Orifice (EVO)/Passlock module receives the vehicle speed information through the Vehicle Control Module (VCM) of the gasoline engines, or the Powertrain Control Module (PCM) of the diesel engines, and the class 2 data line. With the vehicle speed information, the EVO/Passlock module compares the vehicle speed signal received from the VSS with the vehicle speed data received from the class 2 data line. The VSS is a permanent magnet sensor producing an AC signal with varying frequency. The VSS is mounted in the transmission, or the transfer case in selectable four wheel drive models, and is driven off the output shaft. The VSS produces a pulsing AC voltage and the number of pulses increase with the vehicle speed. The VCM/PCM supplies the vehicle speed signal to the instrument cluster and to the EVO/Passlock module.

CONDITIONS FOR SETTING THE DTC
1. The steering wheel rotation sensor signal circuit voltage is less than 0.2 volts.
2. The above condition is met for 1 second.

ACTION TAKEN WHEN THE DTC SETS
The Electronic Variable Orifice (EVO)/Passlock module does not send any current to the PS solenoid actuator. This causes retraction of the PS solenoid actuator. This provides the maximum fluid flow and the full power steering assist at all times.

CONDITIONS FOR CLEARING THE DTC
- A history Diagnostic Trouble Code (DTC) will clear after 100 consecutive ignition cycles have occurred without a fault.
- The history and the current DTC can be cleared by using the scan tool.

DIAGNOSTIC AIDS
The scan tool will read the steering wheel position in volts. With the ignition switch in the ON position, and as the steering handwheel speed sensor is rotated, the voltage reading should be 0.2-4.9 volts. The 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 scan tool, scan the handwheel speed sensor.
- Above 0.2 volts.
- Turn the steering wheel.
- The scan tool display should increase from above 0.2 volts and below 4.9 volts as the steering wheel is turned one quarter revolution (90 degrees).

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Part 2 Of 2:

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step prompts the technician to complete some basic checks and to store the Snapshot data. This creates an electronic copy of the data taken when the fault occurred. Refer to the stored information in the scan tool as necessary. Step 2 also verifies when the voltage is between 0.2-4.9 volts. The Electronic Variable Orifice (EVO)/Passlock module uses this voltage in order to detect changes in the rate of steering. The system voltage should increase and decrease proportionately to the steering wheel rotational speed. If the voltage is not within the specifications, an appropriate DTC sets.
In addition to the DTC diagnosis, check for binding, grinding or damaged steering wheel rotation sensor.
5. This step simulates a high voltage signal, which identifies an open in the signal circuit.
7. This step checks for voltage with a Digital Multimeter (DMM) while probing the signal circuit of the steering wheel rotation sensor. The signal circuit of the steering wheel rotation sensor shorts to ground, if voltage is present.
11. This step checks the terminals for any improper mating, broken locks and physical damage of the wiring harness prior to the replacement of the EVO/Passlock module.