C0305

Circuit Description
The front propshaft speed sensor is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage. The AC voltage level and number of pulses increases as speed increases. The module converts the pulsating AC voltage to a propshaft RPM which is used for calculations, and to monitor the difference between the front and rear propshaft speed. It is also used in the AUTO (Adapt) mode of operation to determine the amount of slip and the percent of torque to apply to the front axle The module only looks at this input when the vehicle is in AUTO (Adapt) mode, 4H, and 4L ranges. The propshaft RPM can be displayed with a scan tool. The module only monitors this input when the vehicle is AUTO, 4H, or 4L.
This DTC detects an open, short to ground, or faulty sensor.
Conditions for Setting
The DTC The system will log 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 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 10 mph.
Action Taken When the DTC Sets
^ All Shifts to AUTO (Adapt) mode will be disabled. If the current mode is AUTO, the system will not allow any further adaptive events (correct slip).
^ The SERVICE indicator (AWD/4WD) lamp will be latched on 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 no longer exists.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ History DTCs can be cleared using a scan tool.








Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
4. This step determines if the front speed sensor is able to generate AC current and indicates that both the sensor and wiring to the transfer case shift control module is good.
5. This step measures the internal resistance of the front speed sensor and whether or not it is within acceptable limits.
7. This step determines if circuit 401 has a short to voltage.