Diagnostic Instructions
DTC Descriptor
DTC C0305: Front Speed Sensor Malfunction
Circuit/System 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 increase 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:
| • | To monitor the difference between the front and rear propshaft speed |
| • | In the AUTO or the Adapt mode of operation, to determine the amount of slip and the percent of torque to apply to the front axle |
The module accesses this input when the vehicle is in AUTO 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.
Conditions for Running the DTC
| • | System voltage is 9-18 volts. |
| • | 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 front axle is engaged. |
| • | The 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 mode are disabled. If the current mode is AUTO, 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 clears the DTC if the condition for setting the DTC is not currently present. |
| • | A history DTC clears after 100 consecutive ignition cycles without a fault present. |
| • | History DTCs can be cleared using a scan tool. |
Reference Information
Schematic Reference
Transfer Case Control Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Transfer Case Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
