OBD-II Code · Body
B1421
Driver Seat Position Sensor
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$100–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Driver seat position sensor fault.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Memory seat doesn't work
Likely causes
- Failed sensorMost common
- Wiring
Read the full diagnostic procedureB1421 means the SRS/airbag control module sees the side crash sensor module circuit reporting open — the side-impact sensor mounted in the B-pillar o…
B1421 means the SRS/airbag control module sees the side crash sensor module circuit reporting open — the side-impact sensor mounted in the B-pillar or front door is either electrically disconnected, has a broken internal squib bridge, or has shifted out of its mounting tolerance enough that the module can no longer verify it. On most modern platforms each side crash sensor is a 2-wire device with a measured squib resistance of 1.5-3.0 ohms between the pins when intact; an open circuit reads infinite ohms.
Diagnostic order
- DO NOT probe airbag circuits with a standard DMM under power — back-probing under battery voltage can fire a live squib. Disconnect the battery, wait at least 10 minutes for the SRS capacitor to discharge per FSM spec, then ohm the sensor circuit.
- Inspect the sensor mounting in the B-pillar or door — sensors are torque-spec critical, typically 8-12 Nm, and a loose sensor or one mounted with a missing isolator washer will throw an open even if the sensor itself is fine.
- Inspect the wiring harness through the door jamb / B-pillar grommet — repeated door slams fatigue the wires inside the rubber boot.
- Replace the sensor with an OEM part (aftermarket SRS components are a no-go for liability and crash performance). Misdiagnosis caveat: side-crash sensors are mounted in the B-pillar or door — if the airbag light came on after a quarter-panel hit, door slam from a parking-lot bump, or an aftermarket speaker install, the sensor often just shifted out of mounting tolerance or has a chafed pigtail; reseat and retorque before quoting a $200-$500 sensor plus dealer programming.
Vehicle-specific patterns2002-2016 Honda Accord/Civic/CR-V/Odyssey across multiple model years carry NHTSA recalls for Takata passenger-side and driver-side inflators that th…
- 2002-2016Honda Accord/Civic/CR-V/Odyssey across multiple model years carry NHTSA recalls for Takata passenger-side and driver-side inflators that throw a constellation of SRS codes including B1421 alongside open/short codes on the front impact sensors — always run the VIN through the NHTSA recall database before quoting any airbag work, because the airbag itself may be free at the dealer.
- 2008-2010Ford F-250/F-350/F-450 SuperDuty commonly throws B1421 alongside a no-start of the Occupant Classification Sensor (OCS) zero-set procedure — the OCS mat under the passenger seat needs to be rezeroed via IDS after any seat R&R, and a missed rezero throws SRS codes including B1421.
- 2005-2010Chevy Cobalt, Pontiac G5, and HHR carry the well-known ignition-switch / clock-spring recall that drives B1421 alongside steering-wheel airbag codes — recall coverage is open at GM dealers for affected VINs.
- 2003-2010Mercedes-Benz E-class W211 throws B1421 from rear seat-belt buckle pretensioner harness chafe at the seat track.
Estimated repair$0 (NHTSA recall coverage on Takata or GM ignition switch) to $850 (OEM side crash sensor plus airbag module reset).
Look up another code
B1421 — frequently asked
What does a B1421 code mean?
Driver seat position sensor fault.
What causes a B1421 code?
Common causes: Failed sensor; Wiring.
What are the symptoms of a B1421 code?
Typical symptoms: Memory seat doesn't work.
Is it safe to drive with a B1421 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $100-$500.
How do I diagnose a B1421 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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