P05B8: Restraint Deployment Signal Circuit/Open

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. P05B8 means the wired signal line is open – no valid rest level arrives. After a real crash the fuel cut-off may then not be triggered via this line. No manufacturer document available to us uses this code; it is a safety function, not an emission-relevant monitor, so usually without warning lamp.

Symptoms

• Code stored, driving usually normal
• Possibly message that fuel cut-off is unavailable
• No check engine light

Most likely causes

• Signal wire or connector between restraint and engine module open (e.g. after accident repair or seat removal)
• Corroded or spread pin at either module
• Replacement module not configured
• Restraint module output stage

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery, connectors, and wiring
2. Check the continuity of the wire between the component and the control module.
3. Read the live data with a scanner
4. Follow the manufacturer's service manual

Good to know

• Repair difficulty: medium

What each character of P05B8 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 5: Speed and idle
• B8: Specific fault in that system

Frequently asked questions

Can I keep driving with code P05B8?

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 P05B8?

The most common causes are: signal wire or connector between restraint and engine module open (e.g. after accident repair or seat removal); corroded or spread pin at either module; replacement module not configured.

Related codes

• P05B9Restraint Deployment Signal Circuit Low
• P05BARestraint Deployment Signal Circuit High
• P05BBRestraints Deployed
• P0230Fuel Pump Primary Circuit
• P0627Fuel Pump A Control Circuit/Open
• U0151Lost Communication with Restraints Control Module

Sources

• static.nhtsa.gov: MC 10142192 9999
• patents.google.com: en
• law.cornell.edu: 13 CCR 1968.2

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.