Front Axle Switch Circuit Signal Invalid
Table of contents
C0378 GMC Possible Causes
- Faulty Front Axle Switch/Actuator
- Front Axle Switch/Actuator harness is open or shorted
- Front Axle Switch/Actuator circuit poor electrical connection
How do I fix code C0378 GMC?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Tech Notes
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Cost of diagnosing the C0378 GMC code
The cost of diagnosing the C0378 GMC code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Anti-Lock Brake System (ABS) Warning Light ON
- Engine Light ON (or Service Engine Soon Warning Light)
C0378 GMC Description
The front axle control circuit consists of an electric motor actuator which engages and disengages the front axle. The front axle actuator motor consists of a permanent magnetic motor, a worm gear controlled plunger, a front axle switch and an electronic control circuit within the actuator assembly. The axle switch signal circuit will have 12 volts when in any 4WD mode or AWD mode and 0 volts when in 2 high or neutral. The front axle actuator consists of the following circuits:
– The front axle control circuit, which is also connected to the transfer case shift control module
– The front axle switch circuit, which is also connected to the transfer case shift control module
– An ignition 3 voltage circuit
– A ground circuit
When a shift to AUTO 4WD, 4HI, or 4LO is requested, the transfer case shift control module engages the front axle by grounding the front axle control circuit through a current limiting driver. This DTC detects a short to ground, short to voltage or an open circuit on the switch signal circuit.