B1C49 – PS Pretensioner Squib Open

The Mitsubishi fault code B1C49 – Passenger Seatbelt Pretensioner Squib Open Circuit is a manufacturer-specific diagnostic trouble code stored by the SRS (Supplemental Restraint System) airbag ECU on Mitsubishi vehicles. It indicates that the SRS control module has detected a complete break in the electrical circuit serving the squib (pyrotechnic initiator) of the front passenger seatbelt pretensioner. With B1C49 active, the passenger pretensioner cannot be guaranteed to fire in a collision, leaving the front passenger without full seatbelt restraint protection at the moment it is most needed. The SRS warning light will be continuously illuminated.

What Does B1C49 Mean on a Mitsubishi?

Seatbelt pretensioners use a small pyrotechnic squib to instantly retract slack from the belt webbing in a collision, holding the occupant firmly against the seat in the critical moments before airbag deployment. The SRS ECU continuously supplies a low-level monitoring current through each pretensioner squib circuit and compares the measured resistance against a tightly defined calibration window — typically just a few ohms, specific to the pretensioner type. B1C49 is stored when the SRS ECU measures infinite or near-infinite resistance on the passenger pretensioner squib circuit, indicating a complete break somewhere between the ECU and the pretensioner unit. The firing signal cannot reach the squib in a deployment event, rendering the pretensioner inoperative.

Symptoms of B1C49

B1C49 presents with the following indicators:

• SRS warning light continuously illuminated on the instrument cluster
• B1C49 stored in the SRS/airbag ECU when scanned with MUT-III or a compatible scanner
• Passenger seatbelt pretensioner inoperative — will not fire in a collision event
• No driveability symptoms — B1C49 is a purely electrical SRS fault
• Other SRS functions may remain operational, but the overall SRS system is flagged as degraded
• Potential roadworthiness failure in markets where a permanently illuminated SRS warning light is a testable item at inspection

Common Causes of B1C49

• Previously fired passenger pretensioner squib — the most common cause; a pretensioner that activated in a prior collision has a permanently severed squib circuit and must be replaced
• Corroded or unseated yellow SRS connector at the pretensioner or under the seat — the shorting bar–equipped SRS connectors in the passenger seat area are exposed to moisture, foot traffic, and disturbance during seat adjustment or removal
• Broken, chafed, or pinched squib wiring harness — harness sections that flex with seat adjustment or pass through seat frame apertures are particularly vulnerable to fatigue fractures and chafing damage
• Internal squib failure in an unfired pretensioner — the pyrotechnic initiator element can fail internally on older or high-mileage vehicles without the pretensioner having deployed
• Corroded or spread SRS ECU connector pin — an open at the ECU end of the circuit rather than at the pretensioner unit itself
• Improper seat removal and refitting — SRS connectors disconnected without following the SRS disable protocol, or not correctly reseated and locked after refitting the seat
• Water ingress under the passenger seat — a frequent cause of corrosion in the floor-level SRS harness connectors, particularly after flooding, heavy rain, or wet mat use

Common Misdiagnoses

• SRS ECU replaced without tracing the circuit: The ECU is rarely the cause of B1C49. The open circuit is almost always in the pretensioner unit, the harness, or a connector. Full circuit isolation using a break-out box is required before any module replacement is considered.
• Squib circuit tested with a standard multimeter: Probing squib terminals with an unregulated DMM is a recognised deployment hazard — even a small test current can theoretically fire the squib. Only approved SRS break-out boxes and resistance simulators should be used for squib circuit measurement.
• Code cleared without repairing the open circuit: B1C49 is a current fault actively monitored on every ignition cycle. It returns immediately after clearing if the root cause has not been resolved.
• Connector reseated without inspecting for corrosion: Physically pushing a corroded connector back into place may appear to resolve the fault temporarily but will not reliably eliminate the open circuit. All SRS connector contacts must be inspected, cleaned, and verified before reconnection.
• Pretensioner assumed fired without visual confirmation: Always confirm whether the pretensioner has physically deployed before condemning it — an unfired pretensioner with an internal squib failure is a different and more straightforward repair than a post-collision unit.

Affected Mitsubishi Vehicles

Tools & Equipment Required

Step-by-Step Diagnosis

• 1
  Disable the SRS System Before Any WorkSwitch off the ignition, remove the SRS fuse, and disconnect the battery negative terminal. Wait a minimum of 60 seconds before touching any SRS component, connector, or wiring. This allows the SRS backup capacitor to fully discharge and eliminates the risk of accidental pretensioner firing.
• 2
  Confirm B1C49 with a Full SRS ScanReconnect power and use MUT-III or equivalent to read all stored SRS fault codes. Note whether B1C49 is current or historical, and record any additional SRS codes that may point to a shared wiring or connector fault affecting multiple squib circuits simultaneously.
• 3
  Check for Prior Collision EvidenceBefore any electrical testing, inspect the passenger seat, B-pillar, and belt assembly for signs of previous collision damage or repair. A fired pretensioner produces a fully retracted, locked belt webbing that cannot be pulled out or re-latched. If the pretensioner has fired, replacement is the only repair — no electrical diagnosis is needed.
• 4
  Inspect the Under-Seat and B-Pillar SRS ConnectorsWith SRS disabled, slide the passenger seat to both extremes and inspect all yellow SRS connectors accessible from beneath the seat and at the B-pillar pretensioner anchor. Check for corrosion, bent or pushed-back pins, moisture, and incomplete secondary lock engagement on each connector body.
• 5
  Measure Squib Circuit Resistance with a Break-Out BoxConnect an approved SRS break-out box at the SRS ECU harness connector. Measure resistance on the passenger pretensioner squib circuit. An open (OL / infinite) reading with the pretensioner connected confirms either a wiring open or an internal squib failure. Disconnect the pretensioner connector and re-measure — if the open moves to the harness side, the wiring is at fault; if the circuit reads correctly with the pretensioner disconnected, the pretensioner squib has failed internally.
• 6
  Trace the Squib Harness if the Open is in the WiringRoute out the pretensioner squib harness from the seat area and B-pillar back toward the SRS ECU, checking all intermediate connectors and areas where the harness may have been pinched, chafed under a seat rail, or disturbed during previous seat or carpet removal. Pay close attention to sections that flex with seat adjustment and to any harness pass-throughs in the seat frame metalwork.

Scanner Readout Explained

====================================================
  MITSUBISHI MUT-III SE — DIAGNOSTIC REPORT
====================================================
  Vehicle:     2020 Outlander PHEV (GG3W)
  Date:        2025-03-27  10:44:19
====================================================
MODULE: SRS / AIRBAG ECU
----------------------------------------------------
  B1C49  Passenger Seatbelt Pretensioner Squib — Open Circuit
         Status:       Confirmed / Current
         Freeze Frame:
           Squib Circuit Resistance:   OL (open, no continuity)
           Expected Resistance Range:  2.0–3.0 Ω (typical squib spec)
           SRS Warning Lamp:          ON
====================================================
  LIVE DATA (SRS System Status)
====================================================
  Driver Front Airbag Squib:              OK
  Passenger Front Airbag Squib:           OK
  Driver Seatbelt Pretensioner Squib:     OK
  Passenger Pretensioner Squib:           OPEN CIRCUIT — FAULT ACTIVE
  Side Curtain L Squib:                   OK
  Side Curtain R Squib:                   OK
  Seatbelt Pretensioner L:                OK
====================================================
  NOTE: SRS system flagged as degraded.
  Passenger pretensioner deployment
  not guaranteed in collision event.
====================================================

Step-by-Step Repair Guide

Repair Path A: Passenger Pretensioner Unit Replacement

• 1
  Disable the SRS SystemRemove the SRS fuse and disconnect the battery negative terminal. Wait a minimum of 60 seconds before proceeding. Do not begin pretensioner removal until this wait period has fully elapsed and you have confirmed there is no residual voltage at the battery terminal.
• 2
  Access the Pretensioner UnitDepending on the model year and pretensioner type, access may require removal of the B-pillar lower trim, partial passenger seat removal, or both. Refer to the OEM workshop manual for the correct trim removal sequence and fastener locations specific to your vehicle.
• 3
  Disconnect the Squib ConnectorLocate the yellow SRS connector at the pretensioner unit. Press the secondary lock release and disconnect carefully. The integrated shorting bar will short the squib terminals on disconnection, preventing any residual current from reaching the squib during the repair procedure.
• 4
  Remove and Dispose of the Faulty UnitUnbolt the pretensioner from its anchor point. Handle the unit carefully — even an unfired pretensioner is a live pyrotechnic device. Follow local regulations for disposal of pyrotechnic automotive components. Do not attempt to disassemble the unit under any circumstances.
• 5
  Fit the OEM Replacement UnitInstall the new OEM pretensioner and torque the anchor bolt to the workshop manual specification — pretensioner anchor torque is a safety-critical value that must not be estimated. Reconnect the yellow SRS connector firmly until the secondary lock clicks fully and positively into place.
• 6
  Re-enable SRS, Clear the Code & VerifyRefit all trim and seat components to torque, reconnect the battery, and refit the SRS fuse. Use MUT-III to clear B1C49 and run a full SRS system check. Confirm the SRS warning light extinguishes and that no further SRS codes are stored.

Repair Path B: SRS Harness Open Circuit Repair

• 1
  Isolate the Fault Location in the HarnessWith SRS disabled and using an approved break-out box, segment-test the squib harness to identify which section carries the open — from the pretensioner to the first intermediate connector, or from there to the SRS ECU. This narrows the physical search to a specific harness run and avoids unnecessary dismantling.
• 2
  Locate and Repair the BreakCarefully trace the harness in the identified segment. Common damage points are where the harness flexes under the seat rail during adjustment, at routing clip edges, and at any point where previous interior work has disturbed the original cable routing. Repair using an OEM-specification SRS harness repair kit — confirm with the workshop manual whether splice repairs are permitted on this specific squib circuit before proceeding.
• 3
  Verify Circuit Resistance, Re-enable SRS & ClearBefore refitting any trim or the seat, confirm the squib circuit resistance is within the specified window using the break-out box. Reconnect the battery and SRS fuse, clear B1C49 with MUT-III, and confirm the SRS warning light extinguishes with no returning codes.

Repair Path C: SRS Connector Cleaning and Reseating

• 1
  Disable SRS & Access the Affected ConnectorsFollow the full SRS disable procedure. Slide the passenger seat fully forward and rearward to expose all under-seat and B-pillar SRS connectors in the passenger pretensioner circuit. Identify every yellow connector that forms part of the B1C49 squib circuit path.
• 2
  Clean the Connector ContactsDisconnect each affected SRS connector carefully. Inspect both male and female pins for green oxidation, corrosion, or moisture residue. Apply electrical contact cleaner and allow to dry fully before applying a light coat of dielectric grease to all pin faces.
• 3
  Reseat, Verify & ClearReconnect all SRS connectors firmly — the secondary lock must click fully into position on each one. Use a break-out box to confirm squib circuit resistance is within specification before re-enabling the SRS system. Clear B1C49 with MUT-III and confirm the SRS warning light extinguishes.

Repair Cost Estimates

Prevention & Maintenance Tips

• Always follow the full SRS disable procedure before removing the passenger seat — improper seat removal is the most common trigger for B1C49 outside of a prior collision
• Inspect under-seat and B-pillar SRS connectors for moisture and corrosion at every major service — floor-level connectors are particularly exposed to water ingress from wet footwear and car washing
• Never route cables, fit accessories, or secure cargo tie-down points near the SRS harness beneath the passenger seat — any contact with the squib harness risks chafing or pinching damage
• Use OEM or OEM-equivalent pretensioner units only — aftermarket units may not meet the precise squib resistance specification monitored by the SRS ECU and may generate a new fault code immediately after installation
• Always clear and verify SRS codes after any seat, carpet, or dashboard repair — an illuminated SRS warning light after unrelated interior work is a frequent post-service complaint with a straightforward preventable cause
• Address the SRS warning light without delay — a degraded SRS system cannot be relied on to provide full occupant protection in a collision

Frequently Asked Questions

Can I drive my Mitsubishi with B1C49 stored?

The vehicle remains driveable, but the passenger seatbelt pretensioner cannot be guaranteed to fire in a collision, leaving the front passenger at increased risk of injury in a significant impact. In many markets a permanently illuminated SRS warning light is also a roadworthiness failure point at inspection. The fault should be diagnosed and repaired as soon as possible.

Will B1C49 clear itself after a connector is reseated?

No. B1C49 is stored in SRS ECU memory and must be actively cleared using MUT-III or a compatible scanner. Even after the open circuit is fully repaired and squib circuit resistance is confirmed within specification, the code and SRS warning light will remain until cleared with a scan tool.

Can I test the pretensioner squib with my multimeter?

No. Using a standard digital multimeter directly across squib terminals is a recognised pretensioner deployment hazard — even the small current from a DMM ohms function can theoretically fire the squib. Only an approved SRS squib resistance simulator or a dedicated SRS break-out box should ever be used for squib circuit resistance measurement.

How do I know if the passenger pretensioner has already fired?

A fired pretensioner will have a fully retracted belt that locks completely and cannot be pulled out or re-latched in normal use. The retractor or pretensioner housing may also show signs of heat or gas discharge. If the belt operates normally and retracts and latches correctly, the pretensioner has not fired and the fault is electrical — either an internal squib failure, a wiring open, or a connector issue.

Is B1C49 likely to appear after the passenger seat has been removed and refitted?

Yes — this is one of the most common real-world triggers for B1C49. If the passenger seat was removed during carpet replacement, detailing, or floor repair and the yellow SRS connectors were disconnected without following the correct disable procedure, or were not fully reseated and locked after refitting, B1C49 will be stored on the next ignition cycle. Always inspect all under-seat SRS connectors after any seat removal work before clearing codes.

Can an aftermarket pretensioner be used for the repair?

Aftermarket pretensioner units carry significant risk on SRS systems. The squib resistance specification is narrow and type-specific — an incorrectly specced unit may generate a new fault code immediately after installation or may not perform to OEM deployment standards in a collision. OEM or OEM-equivalent parts are strongly recommended for all pretensioner replacements.

Does the SRS ECU need replacing if B1C49 returns after a new pretensioner is fitted?

Only after thorough circuit tracing has confirmed continuity throughout the entire squib harness from the pretensioner connector all the way to the SRS ECU connector pins with no open detected anywhere in between. Corroded or spread terminals at the ECU connector are a more common cause of a persistent open than an internal ECU failure and should be inspected carefully before any module is condemned.

How long does a passenger pretensioner replacement typically take?

For a technician with the correct workshop manual and tools, the repair typically takes one to two hours depending on trim access requirements for the specific model year. Code clearing and SRS system verification with MUT-III adds a further 15–20 minutes. Vehicles requiring full seat removal for pretensioner access will sit toward the upper end of that range.

Conclusion

Mitsubishi B1C49 – Passenger Seatbelt Pretensioner Squib Open Circuit is a high-severity SRS fault that disables the front passenger pretensioner and must be diagnosed and repaired without delay. The most common causes are a previously fired pretensioner following a prior collision, a corroded or unseated under-seat or B-pillar SRS connector, or a wiring open introduced during seat removal work. Always follow the full SRS disable procedure before working on any component, use an approved break-out box to isolate whether the open is in the pretensioner unit or the harness, replace faulty components with OEM parts only, and clear and verify the repair with MUT-III.