P25BCRegeneration Control Switch Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P25BC is the high-voltage counterpart: the regeneration switch line carries a level near supply voltage that no switch position can produce. A wire chafed against a battery or ignition feed, water in a switch connector or a switch whose internal resistor network has failed are plausible causes. If the switch requests regeneration by pulling the line up, a stuck high could resemble a permanent start command. That matters because a parked regeneration raises idle speed and exhaust temperature sharply; GM bulletin 20-NA-203 tells drivers to stand on level ground outdoors, clear of anything that can burn. Without a reliable switch the engine controller has to rely on automatic regeneration while driving. No manufacturer documents P25BC publicly, so repair follows the vehicle's wiring diagram.
- What you may notice
- Regeneration switch ignored by the engine controller
- Unexpected regeneration messages in the cluster
- Check engine lamp
- Likely causes
- LikelySwitch signal wire shorted to battery or ignition voltage
- PossibleMoisture in the switch connector
- PossibleInternal fault in the switch or its resistor network
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €40 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.