What Does P279F Mean?
The control module is detecting a low voltage condition on the 4WD range signal circuit. The signal voltage is below the minimum threshold for any valid selector position.
Common Causes
40%
Short to ground in range signal wiring harness
30%
Failed 4WD range selector switch with internal short to ground
15%
Damaged or corroded connector creating ground path
10%
Control module internal short in input circuit
5%
Pinched or chafed wiring contacting chassis ground
Diagnostic Steps
1
Step 1: Disconnect range selector switch and measure voltage at control module side - should see 5V reference
2
Step 2: Check signal wire for continuity to ground with selector disconnected - should be infinite resistance
3
Step 3: Inspect wiring harness routing for pinch points, chafing against metal, or damaged insulation
4
Step 4: Test range selector switch by measuring resistance to ground in each position
5
Step 5: If wiring and switch test good, suspect control module internal short to ground
Estimated Repair Cost
$100 - $900
Parts + labor, varies by vehicle and location
The control module is detecting a low voltage condition on the 4WD range signal circuit. The signal voltage is below the minimum threshold for any valid selector position.
The most common cause of P279F (Four Wheel Drive (4WD) Range Signal Circuit Low) is: Short to ground in range signal wiring harness
Typical repair costs for P279F range from $100 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Control module may default to safe mode locking vehicle in 2WD or last known position. May be unable to select 4WD when needed for traction or safety in off-road conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P279F to identify the root cause.
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Quick Info
Category
Powertrain
System
Four Wheel Drive / All Wheel Drive System
Difficulty
Type
Generic (SAE)
Recommended Tools
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