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 calculations, and to monitor the difference between the front and rear propshaft speed. It is also used in the AUTO 4WD mode of operation to determine the amount of slip and the percent of torque to apply to the front axle. The propshaft RPM can be displayed with a scan tool.
This DTC detects an open, short to ground, short to voltage or faulty sensor.
This diagnostic procedure supports the following DTC:
DTC C0305 Front Speed Sensor Malfunction
• | The ignition is ON. |
• | The system voltage is 9-16 volts. |
• | The vehicle speed must be greater than 16 km/h (10 mph). |
• | The transmission is NOT in Park/Neutral. |
• | The engine is running. |
• | The front axle is engaged. |
The system logs the DTC if the front propshaft input indicates a speed of less than 16 RPM for 30 seconds.
• | 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 wheel slip. |
• | The SERVICE AWD indicator remains illuminated for the remainder of the current ignition cycle. |
• | The transfer case shift control module clears the DTC when the condition for setting the DTC no longer exists. |
• | A history DTC clears after 100 consecutive ignition cycles without a fault present. |
• | History DTCs can be cleared using a scan tool. |
The numbers below refer to the step numbers on the diagnostic table.
This step tests to see if the malfunction is intermittent.
This step tests the internal resistance of the propshaft speed sensor.
This step tests to see if the propshaft speed sensor can generate a sufficient amount of AC voltage.
This step tests the front speed sensor low circuit for a short to ground, a high resistance, or an open.
This step tests the front speed sensor high circuit for a short to ground, a high resistance, or an open.
This step tests the front speed sensor low circuit for a short to voltage.
This step tests the front speed sensor high circuit for a short to voltage.
This step tests the front speed sensor low circuit for a short to the front speed sensor high circuit.
Step | Action | Value(s) | Yes | No | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Transfer Case Control Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
Does the RPM value vary while driving? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |||||||||
Is the resistance reading within the specified values? | 1300-2700 ohms | Go to Step 4 | Go to Step 10 | |||||||||
Is the voltage reading greater than the specified value? | 0.5 V AC | Go to Step 5 | Go to Step 10 | |||||||||
Did you find an correct the condition? | -- | Go to Step 12 | Go to Step 6 | |||||||||
Test the front speed sensor high circuit for the following conditions:
Did you find an correct the condition? | -- | Go to Step 12 | Go to Step 7 | |||||||||
Test the front speed sensor low circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find an correct the condition? | -- | Go to Step 12 | Go to Step 8 | |||||||||
Test the front speed sensor high circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find an correct the condition? | -- | Go to Step 12 | Go to Step 9 | |||||||||
Test the front speed sensor low circuit for a short to the front speed sensor high circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find an correct the condition? | -- | Go to Step 12 | Go to Step 11 | |||||||||
10 | Replace the transfer case front propshaft speed sensor. Refer to Transfer Case Speed Sensor Replacement . Did you complete the repair? | -- | Go to Step 12 | -- | ||||||||
11 | Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 12 | -- | ||||||||
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |