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Ignition Cylinder Sensor Circuit Failure

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

Never probe a squib circuit with an ordinary multimeter; use only an approved restraint circuit tester or read resistance through the scan tool.

  • BBody
  • 1Manufacturer-specific
  • 4Body
  • 91Sequence number

What does it mean?

B1491 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Passenger’s (Front) Air Bag Module (2nd Squib) System Fault 2 (Open In The Squib Circuit) .

Symptoms

  • Airbag warning lamp on and the code stored as a hard fault
  • Second stage of the passenger airbag would not fire in a severe impact
  • Fault often appears after glovebox, dash or heater work
  • Lamp may flicker over bumps if the connection is intermittent

Likely causes

  • Airbag module connector not fully latched, or its locking tab not pushed home after glovebox or dash work
  • Corroded or spread terminals in the passenger airbag connector
  • Broken or stretched wire in the harness behind the glovebox or along the dash carrier
  • Open second stage squib inside the inflator itself
  • Wrong or non matching airbag assembly fitted, so the second stage loop resistance is out of range
  • Connector shorting bar damaged, holding the circuit apart
  • Open driver or connector fault at the airbag control module end

How to fix it

  1. Turn the ignition off, disconnect the battery and wait for the reserve capacitor to discharge before touching any airbag connector
  2. Unlatch and reseat the passenger airbag connector, checking that the locking tab clicks fully home
  3. Inspect the connector for a bent or missing shorting bar, pushed-back terminals and green corrosion
  4. Check the harness behind the glovebox for stretched, pinched or previously repaired wiring
  5. Substitute a known good load tool in place of the airbag to see whether the fault follows the module or the harness
  6. Repair the harness or connector body; fit proper replacement terminals rather than twisting wires together
  7. Replace the passenger airbag assembly with the correct part number if the open is proven inside the inflator

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.