01221: Side Crash Sensor G179

Hardware fault

What 01221 means

G179 is the sensor that tells the controller a side impact is happening on the driver side. It has to respond fast enough to fire a side airbag within a fraction of a second, which is why the controller monitors it closely and shuts the system down when the sensor reports a problem or stops reporting properly.

These sensors mount in the door or the pillar structure, bolted to sheet metal where they can feel the impact directly. Doors get wet inside as a matter of course, since that is what the vapor barrier and the drains are for, and a blocked drain or a torn barrier puts water right where the sensor and its connector live.

Common causes

• Water inside the door reaching the sensor or its connector after a drain clogged
• A torn vapor barrier letting water run onto the sensor mounting area
• Sensor damage or a bent bracket from a prior side impact or door repair
• Corroded terminals in the connector at the door or pillar
• A harness conductor broken in the door jamb boot from years of door movement

Crash data or hardware fault?

01221 reports the sensor's condition as the controller sees it right now, so it is a hardware fault rather than a locked crash record. Correct the problem and the fault stops being reported. Crash data is written into the controller after a deployment and stays there permanently, which is a separate situation requiring a bench reset.

Does our reset clear it?

Nothing about a reset dries out a wet sensor or repairs a broken wire in the door jamb. The controller checks again and stores 01221 right back. Repair or replace the sensor first. Our mail-in reset is for a controller locked on crash data, and on a car that took a side impact, sensors and controller both need attention in order.

Which makes throw it

G179 is the driver side crash sensor on both Audi and Volkswagen. The component name and the mounting approach are consistent across the two brands.

What to do next

Open the door panel and look for water staining on the barrier and around the sensor, because a clogged drain explains most of these and needs fixing whether or not you replace the sensor. Check the harness where it passes through the jamb boot, since that is where conductors break from door movement. If the wiring and connector are sound and the fault stays, replace the sensor with a genuine OEM unit, which we stock for Audi and VW. Related codes: 01220, 01222, B1695.