OBD-II code · Powertrain (generic, extended)
P25BB Regeneration Control Switch Circuit Low
Regeneration control switch input reads stuck low — short to ground or stuck-closed contact. The ECM may see a constant regen request which it cannot service while the vehicle is moving.
Is it safe to drive with P25BB?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySwitch wire shorted to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- Parts involved
- Regen Request Switch
Related codes
- P25BARegeneration Control Switch Circuit/Open
- P25B8Auxiliary Ignition Switch On/Start Position Circuit Low
- P25B9Auxiliary Ignition Switch On/Start Position Circuit High
- P25BCRegeneration Control Switch Circuit High
- P25BDUnmetered Fuel - Forced Engine Shutdown
- P25BEAlternative Fuel Disable Control Circuit / Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.