P0836 and related codes: four wheel drive switches, transfer case and traction input

What does P0836 mean?

On cars with selectable four wheel drive, switches tell the computers whether high, low or two wheel drive is engaged, and the transfer case module can ask the engine computer to light the warning lamp when it finds a fault of its own (P0800). The driveline disconnect switch reports whether a front axle or a driveshaft has been uncoupled. The traction control input carries the request to cut engine power when a wheel spins. A wrong signal can leave four wheel drive unavailable or stuck in, or traction control off.

What causes P0836?

1. A switch on the transfer case or an axle exposed to water, mud and salt
2. A damaged wire or connector under the car
3. A transfer case shift motor or module fault, which P0800 passes on
4. A wheel speed or ABS fault behind the traction control input codes

What to check first for P0836

• Read the transfer case and ABS modules too, not only the engine computer
• Check whether four wheel drive engages and disengages, and whether the dash display agrees
• Inspect the switches and connectors on the transfer case and axles
• Watch the switch states on a scan tool while changing modes, with the car stopped as the owner's manual says

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