P2839Shift Fork B Position Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2839 covers the other end of the scale: the fork B input is pinned high. GM's 2023 Corvette table for rod 2 sets it when pulses stop and the pin carries more than 3.5 V, or once the duty cycle passes 92 %. The test runs all the time except during cranking, and only while system voltage lies between 8.75 and 18 V and reference A between 4.5 and 5.5 V; 150 ms of the condition produce a Type A code. Ford's TR9070 lists P2839 for rod sensor 2 when the pulse width climbs above its window and the input stays at one, and on the 8G-DCT Mercedes-Benz reserves it for a fork B sensor with a short to battery positive. Check the harness for a signal wire rubbing against a supply line and confirm the sensor ground before replacing the sensor or module.
- What you may notice
- Warning lamp and fault message in the cluster
- Fork B gears blocked, fewer gears available
- Reduced acceleration in the substitute program
- Likely causes
- LikelySignal wire of the fork B sensor touching the 5 V or battery supply
- PossibleOpen sensor ground letting the output float high
- RareSensor output stage stuck in the high state
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.