C0305

DTC C0305
Circuit Description
The front propshaft speed sensor is a permanent magnet generator. The permanent magnet generator produces a pulsing AC voltage. The AC voltage level and number of pulses increases as speed increases. The transfer case shift control module converts the pulsating AC voltage to a propshaft RPM which is used for the following functions:

^ Calculations
^ To monitor the difference between the front and rear propshaft speed
^ To determine the amount of slip and the percent of torque to apply to the front axle in the AUTO 4WD mode.

The module accesses this input when the vehicle is in AUTO 4WD mode, 4HI, and 4LO ranges. The propshaft RPM can be displayed with a scan tool.

This DTC detects an open, short to ground, short to voltage or faulty sensor.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0305 Front Speed Sensor Malfunction

Conditions for Running the DTC
^ The ignition is ON.
^ The system voltage is 9 - 18 volts.
^ The vehicle speed exceeds 16 km/h (10 mph).

Conditions for Setting the DTC
The system logs the DTC if the front propshaft input indicates a speed of less than 16 RPM for 30 seconds while all of the following are true:
^ The transmission is not in Park/Neutral.
^ The engine is running.
^ The front axle is engaged.
^ The rear propshaft speed exceeds 512 RPM.
^ The vehicle speed on Class 2 Data bus exceeds 16 km/h (10 mph).

Action Taken When the DTC Sets
^ All shifts to AUTO 4WD mode are disabled. If the current mode is AUTO 4WD, the system does not allow any further adaptive events, such as correcting the slip.
^ The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC
^ The transfer case shift control module will clear the DTC if the condition for setting the DTC is not currently present.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ History DTC's can be cleared using a scan tool.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests to see if the malfunction is intermittent.
3. This step tests the internal resistance of the propshaft speed sensor.
4. This step tests to see if the propshaft speed sensor can generate a sufficient amount of AC voltage.
5. This step tests the front speed sensor low signal circuit for a short to ground, a high resistance, or an open.
6. This step tests the front speed sensor high signal circuit for a short to ground, a high resistance or an open.
7. This step tests the front speed sensor low signal circuit for a short to voltage.
8. This step tests the front speed sensor high signal circuit for a short to voltage.
9. This step tests the front speed sensor low signal circuit for a short to the front speed sensor high circuit.

Step 1 - Step 11:

Step 12: