P279F: Four Wheel Drive (4WD) Range Signal Circuit Low

P279F means the wired 4WD range signal is below the lowest valid level. Many transfer cases report their range through a resistor-coded switch or a position sensor that produces a defined voltage for each of high, low and neutral; a reading under the lowest of these bands points to a short to ground, a missing sensor supply or a sensor that pulls the line down. No manufacturer documents P279F publicly; GM's 2008 Two-Mode Hybrid data list the circuit code P279D for the same range information, and CARB 13 CCR 1968.2 requires range checks on such inputs. The high-side fault is P27A0, the plausibility fault P279E. Look for chafed harness sections near the transfer case and exhaust and for corroded connectors before replacing the encoder.

Symptoms

• 4WD range indicator dark or flashing
• 4WD low or range changes unavailable
• Warning lamp on

Most likely causes

• Range signal wire shorted to ground near the transfer case
• Sensor reference voltage missing
• Range switch or encoder failed with low output

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the fluid level and condition
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Read the input and output speed in live data
4. Check the connector and wiring
5. Check for other related engine codes
6. Consult the manufacturer's procedure for the transmission

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P279F means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 7: Transmission
• 9F: Specific fault in that system

Frequently asked questions

Can I keep driving with code P279F?

Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.

What causes code P279F?

The most common causes are: range signal wire shorted to ground near the transfer case; sensor reference voltage missing; range switch or encoder failed with low output.

Related codes

• P279DFour Wheel Drive (4WD) Range Signal Circuit
• P279EFour Wheel Drive (4WD) Range Signal Circuit Range/Performance
• P27A0Four Wheel Drive (4WD) Range Signal Circuit High

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 08 GRP11 Hybrid HCP

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.