Airbag code
B1421: Restraint circuit fault (varies by make)
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $100 | $400 |
| Labor: 1.3 to 2.2 hours × $125 to $175 an hour | $163 | $385 |
| Fees: shop supplies, disposal, diagnostics | $0 | $40 |
| Total, rounded | $260 | $830 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, seat belt pretensioner / buckle replacement. Which repair your car needs depends on a proper diagnosis.
This code points to a problem in a restraint circuit, but the exact part varies a lot by make. It can mean a seat belt pretensioner, a buckle switch, an occupant sensor or an airbag circuit, so check the scan tool or manual for what yours means. Seat movement and loose plugs under the seat are common causes.
- Safe to drive?
- No, get it looked at first
- Most common cause
- Loose connector under a seat
The airbag system may be turned off, so the airbags may not deploy in a crash. Get it checked soon and avoid putting children in the front seat.
What you may notice
- Airbag light on
- Seat belt light on
- Passenger airbag off light
- Seat sensor acting odd
Common causes, most likely first
- Loose connector under a seat
- Failed seat belt pretensioner or buckle switch
- Damaged wiring after seat movement
- Occupant sensor fault
- Airbag module fault
Check this first
Look at the yellow connectors under the front seats. Do not unplug them with the battery connected, because it can set off the airbag.
Other repairs that sometimes fix B1421
| Repair | Typical range, Boston |
|---|---|
| Airbag / occupant sensor replacement | $240 to $800 |
| Airbag clockspring replacement | $250 to $730 |
| Diagnostic scan (check engine light) | $60 to $290 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
B1421 questions
Can I check connectors myself?
Only a quick look. Leave unplugging to a shop, since airbag circuits can deploy if they are disturbed with the power connected. Do not poke or pull the yellow plugs yourself.
Why the seat belt?
Many cars tie the belt pretensioner and buckle switch into the airbag system, so a fault in a belt can set a restraint code. The warning light on the dash may look the same for each of them.
Do I need a new part?
The scan tool should show which circuit is faulty first, so the shop knows whether it is a connector, a belt, a seat sensor or a bag. Do not accept a parts quote before that is known.
How much does it cost to fix B1421?
The most common fix, seat belt pretensioner / buckle replacement, has a typical range of $260 to $830 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- B0001: Driver airbag circuit fault
- B0020: Side or passenger airbag circuit fault
- B0100: Front impact sensor circuit fault
More airbag codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.