0X930925: Driver Belt Tensioner Circuit

Circuit fault

What 0X930925 means

The driver belt tensioner sits in the retractor, usually inside the B-pillar, and its job is to pull slack out of the belt in the first milliseconds of a crash. A small charge does that work, and the ACSM monitors the circuit to it the same way it monitors an airbag squib. Chassis potential on either wire of that circuit produces 0X930925.

Tensioner wiring lives in a rough neighborhood. It passes down the B-pillar behind trim that gets removed for seat work and headliner work, and on some cars it runs under the seat where feet, cargo, and seat travel can reach it. A grounded conductor anywhere in that run reads the same at the module as a shorted tensioner.

Common causes

• Harness pinched under the seat rail or crushed by seat travel
• B-pillar trim reinstalled with the tensioner wire trapped against bare metal
• Corrosion at the tensioner connector from water running down the pillar or wet carpet
• An internally shorted tensioner charge in the retractor assembly
• Connector terminals bent or pushed back during a belt or seat replacement
• Wiring damaged during seat removal for interior or flooring repair

Crash data or hardware fault?

This is current condition data, not history. The ACSM measures the tensioner circuit and reports what it reads, so the fault clears when the short is repaired. Crash data is history by definition. It records that the restraints fired, it is locked into the module at that moment, and clearing codes with a scan tool leaves it untouched.

Does our reset clear it?

Do the wiring work before the reset. A shorted tensioner circuit is a real fault and the module writes it back as soon as it runs another check. That said, a driver belt tensioner is one of the parts most often fired in a collision, so if this BMW has been wrecked, expect the ACSM to be holding crash data too. That is the part our mail-in reset clears, after the belt and wiring are replaced.

Which makes throw it

0X930925 is BMW specific. The hex numbering comes from BMW diagnostics, and the code applies to BMW models with an ACSM controlling pyrotechnic belt tensioners.

What to do next

Slide the seat through its full travel while watching whether the fault comes and goes, since a pinched harness under the rail shows itself that way. Pull the B-pillar trim next and inspect the connector and wire routing. A tensioner that reads shorted with the harness disconnected needs a replacement belt assembly, and we carry genuine OEM BMW seat belts with working tensioners. Related codes: 0X930913, 0X93092B, B1642.