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Home / DTC / B1C4A — PS.pretensioner circuit short

B1C4A — PS.pretensioner circuit short

Detailed page for trouble code B1C4A.

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Code

B1C4A

MITSUBISHI B — Body

PS.pretensioner circuit short

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Damaged or chafed wiring harness to passenger pretensioner (pin to pin or short to ground/ignition).
  • Corroded or loose connector at the pretensioner or airbag ECU.
  • Failed pretensioner squib (internal short).
  • Contaminated connector (moisture, debris) causing short.
  • Faulty airbag/occupant restraint control module (ECU) driver circuit.
  • Incorrect repairs or aftermarket equipment interfering with wiring (seat rails, sensors).

Symptoms

  • SRS / airbag warning lamp illuminated on dash.
  • Passenger pretensioner circuit disabled or stored as a fault in SRS system.
  • Possible loss of passenger pretensioner function in a crash.
  • Fault may be intermittent with seat position or after exposure to moisture.

What to check

  • Read SRS module trouble codes and freeze/frame data with an appropriate scan tool.
  • Visually inspect passenger seat, seat belt assembly, harness routing and connectors for damage, corrosion or pin damage.
  • With ignition off and battery disconnected per safety procedure, disconnect passenger pretensioner connector and inspect pins for corrosion/shorts.
  • Measure resistance of pretensioner squib between its two terminals (compare to spec).
  • Check for short to ground or to battery voltage on the pretensioner circuit with multimeter.
  • Wiggle test wiring with seat fully forward/back while monitoring resistance or live data for intermittent shorts.

Signal parameters

  • Expected squib resistance: typically a few ohms when intact (refer to factory spec; common range ~0.5–5 Ω).
  • Open-circuit (infinite Ω) indicates broken wire/connector; very low resistance (
  • No steady 12 V should be present on squib pins while ignition is ON (airbag ECU supplies a high-current pulse only during deployment).
  • Continuity should be only between the two squib terminals, not to chassis ground or battery positive.

Diagnostic algorithm

  1. Safety: Disable battery negative terminal and wait the manufacturer-specified time (typically several minutes) to allow SRS capacitors to discharge before touching connectors.
  2. Scan & record: Read and record SRS fault codes and freeze data with a diagnostic tool. Note conditions when fault set.
  3. Visual inspection: Check passenger seat, belt pretensioner, connectors and harness for damage, corrosion, moisture, or pin intrusion. Repair obvious damage.
  4. Connector isolation: With battery still disconnected, unplug the pretensioner connector at the seat. Measure resistance between the two squib terminals and between each terminal and chassis ground/battery +. Compare to spec.
  5. Wiring check: If resistance to ground or battery is present, trace wiring toward the ECU. Use backprobe or continuity tests to locate short (disconnect intermediate connectors as needed). Perform wiggle/seat-movement checks to find intermittent faults.
  6. Component test: If wiring checks good and squib resistance still abnormal, replace the pretensioner assembly and re-test resistance.
  7. ECU check: If wiring and pretensioner are good and fault persists, suspect airbag ECU driver fault. Verify ECU ground and supply, then consider ECU repair/replacement per manufacturer procedures.
  8. Verify: After repair, clear codes and perform SRS self-test with scan tool. Confirm no new codes and SRS warning lamp extinguishes. Re-check after a road drive cycle if required.

Likely causes

  • Connector at passenger seat pretensioner pin(s) pushed together/corroded causing short-to-ground.
  • Wire insulation damaged where it routes over seat rails resulting in intermittent short when seat is moved.
  • Pretensioner squib internal short after partial deployment attempt or water ingress.
  • Seat connector not fully seated after service.

Fault status

⚠️ Status
Passenger pretensioner circuit short detected — circuit shows abnormal low resistance/short to power or ground; pretensioner circuit may be disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

B1C4B B1C4C B1A00 B1800
406

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