After a crash the restraint control module tells the engine module that airbags or belt tensioners have fired; the engine module then cuts the fuel pump (Ford: until the ignition is cycled) and possibly the engine. Depending on the maker the message travels over CAN and/or a dedicated wire with a defined level or voltage drop. P05BB is an event code: the engine module received a valid deployment message. The fuel pump is cut, the engine may stop, doors are unlocked by other modules, and Ford's engine module freezes recorded data. After a crash the restraint module must be replaced; a used module with a stored crash can also cause it. No manufacturer document available to us uses this code; it is a safety function, not an emission-relevant monitor, so usually without warning lamp.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- Engine stops or will not start (fuel cut-off)
- Airbag warning light
- Doors unlocked, fuel cut-off message
Most likely causes
- Real accident with airbag or belt tensioner deployment
- Deployment after a hard underbody hit (e.g. off-road)
- False message from wiring or module fault
- Used restraint module with stored crash fitted
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
What each character of P05BB means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 5: Speed and idle
- BB: Specific fault in that system
Frequently asked questions
Can I keep driving with code P05BB?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P05BB?
The most common causes are: real accident with airbag or belt tensioner deployment; deployment after a hard underbody hit (e.g. off-road); false message from wiring or module fault.
Related codes
- P05B8Restraint Deployment Signal Circuit/Open
- P05B9Restraint Deployment Signal Circuit Low
- P05BARestraint Deployment Signal Circuit High
- P0230Fuel Pump Primary Circuit
- U0151Lost Communication with Restraints Control Module
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.