P2839: Shift Fork B Position Circuit High

Voltage on shift fork B position sensor signal line is above the expected window. Wire shorted to B+ or sensor open.

Medium severity. Can I keep driving?Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

Symptoms

Check engine or transmission warning light on
Harsh, delayed, or missing shifts
Possible limp mode (locked in one gear)
Slipping or shuddering during gear changes

Most likely causes

Signal wire shorted to B+
Open position sensor
Connector pins corroded - high contact resistance

What to check, in order

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

Check the fluid level and condition according to the manufacturer
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Check the transmission connector
Read the data with a transmission-compatible scanner
Measure the solenoid valve circuit
Leave opening the transmission to a specialized repair shop

Good to know

Repair difficulty: hard
It can trigger limp mode.

What each character of P2839 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
8: Transmission
39: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2839?

Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

What causes code P2839?

The most common causes are: signal wire shorted to B+; open position sensor; connector pins corroded - high contact resistance.

Related codes

Sources

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.