OBD Guide
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B1021

Occupant Sensor Control Unit

B1021 is an OBD-II diagnostic trouble code meaning: Occupant Sensor Control Unit. Common causes: malfunction of the passenger sensor control unit, open or short circuit in wiring harness. Estimated repair cost: $56–167.

Severity
⚠️ Medium
Can you drive?
Do not drive — repair immediately
Approx. repair cost
$56–167 (est.)

Symptoms

  • The passive safety system fault indicator is on
  • The passenger airbag does not activate or does not activate correctly
  • Error persists after OBD-II scan

Causes

  • Malfunction of the passenger sensor control unit
  • Open or short circuit in wiring harness
  • Poor contact in connectors
  • Control unit software failure

How to Fix

  1. Check wiring harness and connectors for damage
  2. Test the passenger sensor control unit
  3. If necessary, replace the control unit
  4. Update the unit firmware (if required)

Related codes

B1010B1020B1030

FAQ

What does the B1021 code mean?

B1021 is an OBD-II diagnostic trouble code that indicates: Occupant Sensor Control Unit

What causes a B1021 error code?

The most common causes of B1021 include: Malfunction of the passenger sensor control unit; Open or short circuit in wiring harness; Poor contact in connectors; Control unit software failure.

How do I fix a B1021 diagnostic trouble code?

To fix B1021: Check wiring harness and connectors for damage. Test the passenger sensor control unit. If necessary, replace the control unit. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with B1021?

Do not drive — repair immediately

How much does it cost to fix B1021?

The estimated repair cost for B1021 is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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See also: Russian version · NationStat