Diagnostic Trouble Code (DTC): P0837 – Four Wheel Drive (4WD) Switch Circuit Range Performance

P0837 Code Definition

The P0837 code is a generic powertrain code related to the transmission or gear box. In this case, it means a fault has been found relating to the four wheel drive (4WD) switch circuit.

Codes related to the P0837 include:

• P0836: Four Wheel Drive (4WD) Switch Circuit
• P0838: Four Wheel Drive (4WD) Switch Circuit Low
• P0839: Four Wheel Drive (4WD) Switch Circuit High
• P2771: Four Wheel Drive (4WD) Low Switch Circuit
• P2772: Four Wheel Drive (4WD) Low Switch Circuit Range/Performance
• P2773: Four Wheel Drive (4WD) Low Switch Circuit Low
• P2774: Four Wheel Drive (4WD) Low Switch Circuit High

What the P0837 Code Means

A P0837 code is stored only on all-wheel drive and four-wheel drive vehicles. Actuation of the four-wheel drive system is controlled by the four-wheel drive switch. When this code is stored, the vehicle’s transfer control case system has found a fault or received a reading outside of preset parameters relating to the four-wheel drive system.

Several types of four-wheel drive systems are manufactured to actuate changes between two- and four-wheel drive operation, including fully electronic systems and combinations of engine vacuum and electronically controlled solenoids. Most four-wheel drive switches utilize an on/off contact and will be mounted near the instrument panel. Refer to your vehicle service manual for specifics to your make and model.

What Causes the P0837 Code?

Several problems may cause a P0837 code including:

• Damaged or corroded wiring, harness, and/or connectors
• Damaged or defective four-wheel drive switch
• Damaged or defective four-wheel drive actuator
• Damaged or defective transfer case sensor
• Damaged or defective ECM (most typically if code appears in a two-wheel drive vehicle)

What are the Symptoms of the P0837 Code?

Symptoms of a P0837 code may include:

• Illuminated check engine or warning light
• Erratic or inaccurate temperature gauge
• Vehicle may shift harshly
• Vehicle may fail to shift
• Vehicle may stall when decelerating to stop

How Does a Mechanic Diagnose the P0837 Code?

A mechanic may use several methods to diagnose a P0837 trouble code, including:

• Utilize an OBD-II scanner to check for a stored P0837 trouble code
• Visually inspect all related wires and connectors for visible signs or damage or wear
• Using a digital volt or ohmmeter, check battery voltage on input side of four-wheel drive switch
• Check continuity at the clutch position sensor between four-wheel drive system fuse and input circuit
• Using a digital volt or ohmmeter, check battery voltage on output side of four-wheel drive switch
• Test continuity and resistance between the four-wheel drive switch and ECM

Common Mistakes when Diagnosing the P0837 Code

One common mistake made when diagnosing the P0837 is determining a full transfer case failure when it’s simply a switch or solenoid. Rarely will a full transfer case rebuild be needed as often repairs can fix most of the problems that cause the P0837 code.

How Serious is the P0837 Code?

Because a vehicle’s safe driving operation is may be impacted due to faults that store a P0837 code, this is considered a potentially serious fault. When this code appears, it is recommended that you take your vehicle to a service center or mechanic for diagnosis and repair as soon as possible.

What Repairs can Fix the P0837 Code?

Several repairs can fix a P0837 trouble code and include:

• Repair or replace any damaged or defective wires, connectors or harnesses
• Repair or replace damaged four-wheel drive switch
• Repair or replace open, damaged, or shorted circuits
• Repair or replace damaged or defective ECM (rare)
• Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear

Additional Comments for Consideration Regarding the P0837 Code

Because a P0837 code is only stored on all-wheel drive and four-wheel drive vehicles, if the code appears and your vehicle is a two-wheel drive, it may be a faulty or defective ECM.

Need Help with a P0837 Code?

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.