Fault codeP0839

MODERATE

Four Wheel Drive (4WD) Switch Circuit High

What this code means

Four Wheel Drive (4WD) Switch Circuit High.

P0839 is a generic code: it means the same thing on every make. P0839 belongs to family P08xx — Transmission (continued). Its page explains how to read a code and groups all its codes by part.

Type of fault

The control unit reads a voltage on this circuit above its expected range. Usual causes: a broken wire or a poor ground, a short to a supply voltage, or the component itself. As with a low signal, check the wiring and connector before the part.

Four-wheel-drive switch

On some four-wheel-drive vehicles, a switch or the transfer case tells the control units which drive mode is engaged: two-wheel drive, four-wheel drive, low range.

What you notice

The four-wheel-drive mode indicator does not match the mode selected, a mode that will not engage, sometimes shifts or speed readings that are off.

How to check it

Check the switch and its connector, then the transfer case's position sensor and its wiring under the car, exposed to water and mud.

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
8Transmission (continued)
39P0839