Internal failure of the Restraints Control Module itself, such as corrupted memory or a faulty microprocessor; Low battery voltage or a voltage spike that corrupted the RCM's internal settings; Water intrusion or corrosion inside the RCM connector or housing, damaging internal circuits; Poor ground connection at the RCM mounting point, causing erratic module operation; Aftermarket electronic accessories improperly wired into the airbag circuit, causing electrical interference; A previous accident or deployment event that stressed the RCM beyond its design limits; Manufacturer software glitch requiring an RCM reprogramming or update

DTC codes / B01xx · Airbags, seats, doors, lights and comfort systems / B0100

B0100Restraints Control Module Internal Fault

Q: What does code B0100 mean?

Restraints Control Module Internal Fault. B0100 means the Restraints Control Module (RCM) has reported an internal fault within its own circuitry or memory, so the module can no longer trust its ability to deploy airbags and pretensioners correctly. The computer detected a failure in the RCM's self-test, such as a checksum error, watchdog timeout, or internal component fault, rather than a problem with an external sensor or wiring.

B0100 means the Restraints Control Module (RCM) has reported an internal fault within its own circuitry or memory, so the module can no longer trust its ability to deploy airbags and pretensioners correctly. The computer detected a failure in the RCM's self-test, such as a checksum error, watchdog timeout, or internal component fault, rather than a problem with an external sensor or wiring.

SystemBody

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

Airbag warning light illuminated continuously on the instrument cluster
Passenger airbag indicator may show 'off' or fail to illuminate when expected
Often no symptoms besides the warning light, with all systems appearing to work normally
Airbag system may be disabled, so airbags will not deploy in a collision
In some vehicles, remote keyless entry or other body functions may be affected if the RCM shares a network
Intermittent warning light that comes and goes before staying on permanently

Common causes, most likely first

Internal failure of the Restraints Control Module itself, such as corrupted memory or a faulty microprocessor
Low battery voltage or a voltage spike that corrupted the RCM's internal settings
Water intrusion or corrosion inside the RCM connector or housing, damaging internal circuits
Poor ground connection at the RCM mounting point, causing erratic module operation
Aftermarket electronic accessories improperly wired into the airbag circuit, causing electrical interference
A previous accident or deployment event that stressed the RCM beyond its design limits
Manufacturer software glitch requiring an RCM reprogramming or update

How to diagnose and fix it

Verify battery voltage and charging system health, as low voltage is a common trigger for false internal fault codes
Inspect the RCM connector and mounting area for corrosion, water intrusion, or loose pins
Check and clean the RCM ground connection to ensure a solid, low-resistance path to chassis
Scan all modules for related codes and record freeze-frame data to understand when the fault occurred
Perform any available RCM software update or reprogramming per the manufacturer's service information
If the fault persists after power and ground checks, replace the RCM and perform required initialization or coding
Clear codes and verify the airbag warning light operates correctly through a complete self-test

What the RCM self-test actually checks

A B0100 is often set by a momentary voltage drop during engine cranking, so load-testing the battery before condemning the module saves unnecessary replacements.
The RCM performs a self-test at every key-on, and a single failed check can latch the code permanently until cleared, even if the fault was transient.
Water leaks from a clogged sunroof drain or windshield seal often reach the RCM before any other module, causing internal corrosion that mimics a failed module.
Some vehicles require the RCM to be configured or programmed after replacement, and a used module from another vehicle will not work without proper initialization.
A B0100 does not always mean the module is dead; a poor ground or low voltage can cause the same internal fault flag, so electrical checks come first.

Can I keep driving with B0100?

The vehicle is not safe to drive because the airbag system may be disabled, leaving occupants unprotected in a collision. Have the fault diagnosed and repaired before driving, and avoid any situation where airbag deployment might be needed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.