B1489: Occupant Detection Control Unit Failed

Hardware fault

What B1489 means

Hyundai uses an occupant detecting system to judge what is in the passenger seat, usually through sensors built into the cushion and a control unit that interprets them. That control unit reports its conclusion to the SRSCM, which uses it to arm, suppress, or stage the passenger airbag. B1489 means the control unit has reported its own failure or stopped producing a usable result.

The unit mounts with the passenger seat, so it shares the seat's environment. Spilled drinks, wet carpet, and years of seat adjustment all reach it. It also gets disturbed whenever the seat comes out for upholstery or floor work, which is a common history behind a control unit that stops working right afterward.

Common causes

• Internal failure of the occupant detection control unit
• Liquid reaching the unit from a spill or a wet passenger floor
• Connector corrosion leaving the unit with an unstable supply
• Damage during seat removal or reinstallation
• A unit carried over from another vehicle and never matched to this car

Crash data or hardware fault?

Hyundai classes this as a hardware fault because the component itself has quit rather than a loop drifting out of range. Crash data is a separate record kept by the SRSCM: written after a deployment, locked, and beyond the reach of a scan tool. The two have nothing to do with one another.

Does our reset clear it?

Our mail-in reset addresses control modules holding crash data, and it does not repair an occupant detection unit that has failed internally. Handle the seat side of the system first: confirm power, ground, and connections, then replace the unit if it is genuinely bad. Call 501-988-0611 if you need help sorting out which module in the car actually needs service.

Which makes throw it

Hyundai is the make that reports B1489. It reads on Hyundai scan tools as a failure of the occupant detection control unit itself, distinct from the codes covering calibration and the belt tension sensor.

What to do next

Verify the unit is getting clean power and ground at its connector before condemning it, because an unstable supply can make a healthy unit report failed. Check for water staining in the passenger floor at the same time, since liquid damage is the most common cause. If the unit is confirmed bad, a replacement typically needs the system calibration run afterward for the passenger airbag to arm correctly. Related codes: B1481, B1490, B1015.