B1998: Passenger Sid, Side mount Airbag Circuit Open

B1998 is a critical restraint system fault. The supplemental restraint system (SRS) module continuously monitors the resistance of each airbag squib circuit to confirm it can deploy when needed. An open circuit in the passenger side-mount airbag means that circuit path is broken -- the module cannot send the deployment current, and the airbag will not inflate in a side-impact collision. This is not a code to ignore or drive with long-term.

The open circuit is most commonly in the airbag connector or the wiring harness running through the B-pillar and door sill area to the side airbag module mounted inside the seat or door trim. These harnesses run through high-flex areas and are susceptible to chafing and fatigue breaks, especially in older vehicles or those that have had seat or trim removed. In some cases the airbag squib itself has failed internally, or a clock spring-style connector has worn out. It's worth noting that B1998 can also be set by an aftermarket seat installation where the original side airbag wiring was disturbed.

Airbag circuits require careful handling -- always disconnect the battery and wait the manufacturer-specified time (typically 10-15 minutes) before probing any SRS wiring to allow the backup capacitors to discharge. Resistance measurement of the squib circuit with a dedicated airbag-safe multimeter will confirm whether the fault is in the wiring or the airbag module itself. Given the safety implications, this repair is best handled by a workshop with SRS experience.