The airbag warning light can have many causes: a broken sensor wire, a deployed belt tensioner after an accident, or a crash record stored inside the control unit. Only manufacturer-level diagnostics can read all airbag fault codes and the complete crash record.
Vehicles with an airbag fault no longer have an active protection system. A permanently illuminated airbag warning light should be investigated without delay.
Crash sensor, deployment decision, storage of accident data (crash record). Communicates with all airbag and belt tensioner units.
Typical faults: Crash record stored after accident, internal faults, communication faults to sensors
Diagnosis: Read crash record: timestamp, deployment stage, vehicle speed. Only manufacturer-level diagnostics can read the full data.
Solutions:
Measures deceleration at the front. Sends signal to the ACM. Multiple sensors at different positions.
Typical faults: Sensor defective, wiring break, corroded connector
Diagnosis: Fault code indicates which sensor is affected. Resistance measurement at the sensor connector.
Solutions:
Side crash sensor in doors or B-pillar. Triggers side airbag / curtain airbag.
Typical faults: After side damage, door repair, moisture ingress
Diagnosis: Fault code frequently appears after door/side repair. Check sensor communication.
Solutions:
Pretensions the belt in a crash. Pyrotechnic or electric motor type. Some are reversible; others must be replaced after deployment.
Typical faults: Resistance fault, deployed tensioner, wiring break
Diagnosis: Igniter circuit resistance: 2–3 Ω normal. Too high / too low: tensioner defective.
Solutions:
Read the crash record from the ACM: timestamp, vehicle speed, delta-V (velocity change), deployed systems. Basis for damage analysis and insurance assessment.
Airbag diagnosis: which airbags deployed, which are still operational? Belt tensioners: pyrotechnically deployed = must be replaced.
Repair bodywork and airbag components mechanically. Install new airbag modules. Fit new belt tensioners where required.
ACM with crash record: either reset/clear (if the unit itself is undamaged) or replace and code. Without a reset: airbag warning light stays on permanently, system inactive.
Complete diagnostic scan: no further fault codes, airbag system active again, all sensors communicating. Test drive: airbag warning light extinguishes after start.
Send us the vehicle, model and situation via WhatsApp – we will read the crash record and airbag fault codes and outline the next steps.
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