0X930931: Driver Belt Force Limiter

Circuit fault

What 0X930931 means

Force limiting works by letting the belt pay out in a controlled way past a set load, so the belt restrains without concentrating all the force on the chest. On systems with an adaptive limiter, a small pyrotechnic or switchable device changes that load level during the crash, and the ACSM controls it. Chassis potential on that control circuit causes the module to store 0X930931.

The limiter device is built into the retractor assembly alongside the tensioner, which means the two share a location and often share a harness branch. Seeing a tensioner code together with this one usually points at the common wiring or connector rather than at two separate failures inside the same retractor.

Common causes

• A grounded conductor in the shared retractor harness branch in the B-pillar
• Connector corrosion at the retractor from water running down the pillar
• Wiring crushed or pinched during seat, trim, or carpet work
• An internal short in the force limiter device inside the retractor
• Bent or backed-out terminals at the retractor or module connector
• Insulation worn through where the harness passes a metal edge in the pillar

Crash data or hardware fault?

An active electrical condition is what the module is reporting, which keeps this out of the crash data category. 0X930931 clears once the circuit measures correctly. Crash data is written at deployment and stays put, which is why a wrecked car needs a module reset rather than a code clear even after all the parts are replaced.

Does our reset clear it?

Resetting the ACSM does not lift a short off a wire. Repair the circuit, verify the reading, then clear the light. Adaptive force limiters are single-use on deployment, so if this BMW has been in a crash the retractor assembly has to be replaced regardless of the wiring. Once the parts are in, our mail-in reset clears the deployment record locked in the module.

Which makes throw it

0X930931 comes from BMW hex diagnostics and applies to BMW models with an adaptive belt force limiter on the driver side. The code does not cross over to other makes.

What to do next

Scan for other restraint codes first, because a driver tensioner code beside this one narrows the problem to the shared harness in the B-pillar. Pull the pillar trim and inspect the connector and the wire routing for crush and corrosion. If the limiter reads shorted on its own, the retractor assembly is the part to replace, and we can supply a genuine OEM BMW belt assembly. Related codes: 0X93092B, 0X930937, 46-1X.