P0838: Four Wheel Drive (4WD) Switch Circuit Low
What to do
Drive mode selection may be unavailable or wrong. If the vehicle is used off road, mention it — underfloor wiring damage is a far more likely cause on such a vehicle than a failed switch.
What this code means
The four-wheel-drive switch circuit reads below its valid range, normally a short to ground. The wiring to a transfer case runs along the underside of the vehicle, where road salt, stone damage and water all reach it — and on a vehicle that actually goes off road, so do rocks and branches.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Road damage to underfloor wiring · moderate
- Faulty four wheel drive switch · easy
Less common
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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