NVG 126-NP4 Transfer Case

DTC C0305





Test 1-3





Test 4-12

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 transfer case shift control 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.
This DTC detects an open, short to ground, short to voltage or faulty sensor.

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:
^ Transmission NOT in Park/Neutral.
^ Engine is running.
^ Rear propshaft speed exceeds 512 RPM.
^ Vehicle Speed On Class 2 Data bus exceeds 16 km/h (10 mph).

Action Taken When the DTC Sets
^ All shifts to AUTO, Adapt, mode are disabled. If the current mode is AUTO, the system will not allow any further adaptive events, correct slip.
^ The Service AWD indicator is 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 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 propshaft speed sensor LO circuit for a short to ground, a high resistance, or an open.
6. This step tests the front propshaft speed sensor HI circuit for a short to ground, a high resistance, or an open.
7. This step tests the front propshaft speed sensor LO circuit for a short to voltage.
8. This step tests the front propshaft speed sensor HI circuit for a short to voltage.
9. This step tests the front propshaft speed sensor LO circuit for a short to the FSS HI circuit.