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P0838 is a diagnostic trouble code (DTC) for "Four Wheel Drive (4WD) Switch Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
When a P0838 trouble code is stored it is due to a detection in the four-wheel-drive switch circuit by the Powertrain Control Module (PCM). This trouble code is restricted exclusively to all-wheel or four-wheel-drive vehicles. If the PCM stores this code in a two-wheel-drive vehicle, the PCM is most likely defective. Related codes include a P0836, P0837, and P0839 code.
When the transfer case control system detects an irregular reading issuing from the four-wheel-drive actuator switch circuit, a P0838 trouble code is stored and the Check Engine light illuminates. When the vehicle is in use, the four-wheel-drive switch actuates the four-wheel-drive system and switches between the transfer case gear ratios.
The actuator or four-wheel-drive switch failing is a common cause of a P0838 trouble code. Some other causes of a P0838 trouble code storage include bad sensors, solenoids, or switches, as well as faulty wiring or connectors.
While sometimes a P0838 trouble code can be accompanied by no obvious symptoms, the code can also result in a total transfer case failure. Other symptoms include harsh or failure in shifting or the engine stalling when coming to a stop.
In addition to an advanced scanner and digital volt/ohmmeter, a mechanic also needs a manufacturer's wiring schematic with connectors views to diagnose this code. The mechanic needs to perform the following diagnostic steps:
Rebuilding or replacing the transfer case when replacing a single component would have fixed the problem is one of the most common mistakes made by mechanics when fixing a P0838 trouble code.
The transfer case failure that sometimes accompanies a P0838 trouble code means that vehicle owners should get this code diagnosed and fixed as soon as possible. Coupled with the other common symptoms of a P0838 trouble code can make it difficult to drive the vehicle, especially when attempting to change gears or go into four-wheel drive.
Repairing a P0838 trouble code requires the mechanic to perform the following:
Replace the clutch position sensor if it is not working.
Replace the PCM if faulty. The mechanic also has to reprogram the PCM when replacing it.
YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.