P05B9Restraint Deployment Signal Circuit Low
- Generic OBD-II code · Powertrain
- How the car detects it
- 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. P05B9 means the signal line stays below its valid rest level – usually a short to ground. Where deployment is coded as a voltage drop, a short to ground could resemble a deployment, so makers cross-check with the CAN message. No manufacturer document available to us uses this code; it is a safety function, not an emission-relevant monitor, so usually without warning lamp.
- What you may notice
- Code stored
- Possibly fuel cut-off warning
- No check engine light
- Likely causes
- LikelySignal wire chafed to ground (harness under seat or console)
- PossibleWater in the connector (footwell)
- RareRestraint module output stuck low
- RareEngine module input
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.