B0021-13: Left Curtain Airbag Squib Open

Circuit fault

What B0021-13 means

The left curtain is a long inflatable stored above the headliner and anchored at the pillars. Its igniter sits at the inflator end, usually near the rear pillar, and its wiring runs up the A pillar or along the roof rail back to the control module. B0021-13 is stored when the module test current finds that path broken.

Curtain circuits get disturbed by work that has nothing to do with airbags. Headliner drops for sunroof repair, pillar trim removal for window or speaker work, and roof rack or antenna installs all put hands near that harness. The connector at the inflator is frequently the culprit because it is out of sight once the trim goes back on.

Common causes

• The curtain inflator connector left unplugged after headliner or pillar trim work
• Harness damage along the roof rail from trim clips or interior repairs
• An open igniter inside the curtain airbag inflator
• Water intrusion at a roof seam, sunroof drain, or antenna base reaching the connector
• A pillar trim panel reinstalled with the wiring pinched behind it
• Corroded or backed out terminals at the airbag control module

Crash data or hardware fault?

B0021-13 tracks a live continuity reading and belongs with the circuit codes. The module measures it repeatedly and the code follows the wiring. Crash data is a permanent record written at deployment that no scan tool clear touches, and that difference is what decides whether a module reset is even relevant.

Does our reset clear it?

The reset does not restore continuity in a curtain circuit. Find the open, repair it, and confirm the loop reads correctly before calling the job finished. Where our mail in service fits is on Ram modules that fired in a crash and are locked with deployment data, which is a common situation when a curtain has actually gone off.

Which makes throw it

Our lookup carries B0021-13 under Ram, for the left curtain deployment squib 1 circuit. Trucks without side curtain airbags will never store it, so its presence tells you the cab is equipped with roof rail curtains.

What to do next

Drop the lower A pillar trim and check the curtain connector, because a plug left unlatched after interior work is both the most common cause and the easiest to reach. Follow the harness along the rail looking for pinch damage behind trim clips. Measure the loop at the module end to decide whether the break is in the harness or the inflator. We carry genuine OEM Ram curtain airbags when the inflator is the answer. Related codes: B0020-13, B0028-13, B0001-11.