B1401 – F ABG (1) DR Squib Open

The Mitsubishi fault code B1401 – Front Airbag (1) Driver 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 first-stage squib (pyrotechnic initiator) of the driver’s front airbag inflator. With B1401 active, the driver airbag stage 1 squib cannot receive the firing signal in a collision event, rendering that deployment stage inoperative. The SRS warning light will be continuously illuminated and the fault requires prompt attention.

What Does B1401 Mean on a Mitsubishi?

The SRS ECU continuously supplies a precisely controlled low-level monitoring current through each squib circuit and compares the measured resistance against a tightly calibrated window — typically 2.0–3.0 ohms for a Mitsubishi front airbag squib. B1401 is stored when the SRS ECU measures infinite or near-infinite resistance on the driver front airbag stage 1 squib circuit, indicating a complete break in the circuit somewhere between the ECU and the inflator. The firing signal cannot traverse the open circuit to reach the squib, meaning the driver airbag stage 1 cannot deploy in a collision regardless of impact severity. The designation “(1)” identifies this as the first-stage squib of a dual-stage driver airbag inflator — the primary firing circuit used across the full range of deployment events.

Symptoms of B1401

B1401 presents with the following indicators:

• SRS warning light continuously illuminated on the instrument cluster
• B1401 stored in the SRS/airbag ECU when scanned with MUT-III or a compatible scanner
• Driver front airbag stage 1 inoperative — will not deploy in a collision event regardless of impact severity
• No driveability symptoms — B1401 is a purely electrical SRS fault
• Other SRS functions may remain operational, but the overall 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 B1401

• Failed or worn clock spring (spiral cable / rotary connector) — the driver airbag squib circuit passes through the clock spring on the steering column; a fractured internal conductor is the single most common cause of B1401 on Mitsubishi vehicles
• Previously deployed driver airbag inflator — an inflator that fired in a prior collision has a permanently severed squib circuit and must be replaced along with the clock spring and any other deployed SRS components
• Internal squib failure in an undeployed inflator — the pyrotechnic initiator element can develop an internal open circuit on older or high-mileage airbag modules without the inflator having deployed
• Corroded or unseated yellow SRS connector at the airbag module or clock spring — the shorting bar–equipped SRS connectors at the steering wheel hub and clock spring are susceptible to corrosion and incomplete secondary lock engagement
• Broken, chafed, or pinched squib wiring in the steering column — wiring routed through or around the steering column assembly is vulnerable to damage during steering column repair, wheel replacement, or horn pad removal without SRS disable
• Corroded or spread SRS ECU connector pin for the B1401 circuit — an open at the ECU end of the squib circuit rather than at the inflator or clock spring
• Improper prior repair without SRS disable — disconnecting SRS connectors at the steering wheel hub without following the SRS disable procedure can damage the clock spring internal conductors or the connector shorting bar mechanism

Common Misdiagnoses

• Driver airbag module replaced without checking the clock spring first: The clock spring is the most common cause of B1401 on Mitsubishi vehicles and should be tested before the airbag module is condemned. A new airbag module fitted with a faulty clock spring will generate B1401 immediately.
• Clock spring replaced without verifying squib circuit continuity through the new unit: A replacement clock spring must be confirmed in-circuit using an SRS break-out box before the steering wheel and airbag module are refitted — a transit-damaged or incorrectly fitted clock spring can present an open on the squib circuit from day one.
• Squib circuit tested with a standard multimeter across the squib terminals: Using an unregulated DMM directly across squib terminals is a recognised deployment hazard regardless of the fault type. Only approved SRS break-out boxes and squib resistance simulators should be used for squib circuit measurement.
• Code cleared without identifying and repairing the open circuit: B1401 is a current fault actively monitored on every ignition cycle. It returns immediately after clearing if the root cause has not been resolved.
• SRS ECU replaced as a first step: The ECU is the least probable cause of B1401. Full circuit isolation using a break-out box — starting at the clock spring — is mandatory before any module replacement is considered.

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. The driver airbag is a large-volume inflator directly in front of the driver — the SRS disable procedure and capacitor discharge wait are non-negotiable before approaching the steering wheel hub or clock spring.
• 2
  Confirm B1401 with a Full SRS ScanReconnect power and use MUT-III or equivalent to read all stored SRS fault codes. Confirm B1401 is current. Note any additional SRS codes — particularly a simultaneous stage 2 driver airbag code or a clock spring–related code — that may indicate a shared fault point affecting both squib circuits in the driver airbag circuit path.
• 3
  Check for Prior Collision or Airbag Deployment EvidenceBefore any electrical testing, inspect the steering wheel hub, airbag cover, and horn pad for signs of previous deployment, repair, or replacement. A deployed driver airbag inflator will have a visibly ruptured or missing cover and a fired module. If deployment has occurred, inflator replacement — along with clock spring and any other deployed components — is the required repair path.
• 4
  Measure Squib Circuit Resistance at the SRS ECU Using a Break-Out BoxConnect an approved SRS break-out box at the SRS ECU harness connector. Measure resistance on the driver stage 1 squib circuit. An open (OL / infinite) reading confirms the fault is present at this point. This measurement includes the full circuit path: ECU connector → harness → clock spring → airbag module squib.
• 5
  Isolate the Open to the Clock Spring, Airbag Module, or HarnessWith SRS disabled, access the clock spring connector at the steering column. Disconnect the clock spring from the harness-side connector and re-measure squib circuit resistance at the break-out box. If the open remains, the fault is in the harness between the clock spring and the SRS ECU. If the open clears when the clock spring is disconnected, the open is within the clock spring itself or at the airbag module side of the clock spring — disconnect the airbag module squib connector next to isolate between the two.
• 6
  Inspect Connectors and Trace Wiring as Directed by Isolation ResultsBased on the isolation result, inspect the identified component — clock spring, airbag module squib connector, or harness segment — for the specific open. At the clock spring, check both the harness-side and steering wheel–side connectors for corrosion, unseated pins, and secondary lock engagement. At the airbag module, inspect the yellow SRS connector for the same. In the harness, trace the squib wiring for breaks, chafing at routing clips, or damage from prior column repair work.

Scanner Readout Explained

====================================================
  MITSUBISHI MUT-III SE — DIAGNOSTIC REPORT
====================================================
  Vehicle:     2016 Outlander PHEV (GG3W)
  Date:        2025-03-27  11:03:44
====================================================
MODULE: SRS / AIRBAG ECU
----------------------------------------------------
  B1401  Front Airbag (1) Driver 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 (1):          OPEN CIRCUIT — FAULT ACTIVE
  Driver Front Airbag Squib (2):          OK
  Passenger Front Airbag Squib (1):       OK
  Passenger Front Airbag Squib (2):       OK
  Driver Seatbelt Pretensioner Squib:     OK
  Passenger Pretensioner Squib:           OK
  Side Curtain L Squib:                   OK
  Side Curtain R Squib:                   OK
====================================================
  NOTE: SRS system flagged as degraded.
  Driver airbag stage 1 will not deploy
  in a collision event.
====================================================

Step-by-Step Repair Guide

Clock Spring Replacement

• 1
  Disable the SRS SystemRemove the SRS fuse and disconnect the battery negative terminal. Wait a minimum of 60 seconds. Centre the steering wheel and lock it in the straight-ahead position before beginning — an off-centre steering wheel during clock spring removal will misalign the new unit and can damage the internal ribbon conductor on installation.
• 2
  Remove the Driver Airbag ModuleAccess the airbag module mounting bolts through the rear of the steering wheel hub — typically two or three Torx bolts accessible through holes in the rear of the wheel. Disconnect the yellow SRS squib connector and any horn connectors. Place the airbag module face-up on a flat, stable surface away from the vehicle.
• 3
  Remove the Steering WheelMark the steering wheel-to-shaft spline alignment before removal. Remove the central retaining nut to the workshop manual torque specification and withdraw the wheel using a steering wheel puller — never strike the column end to free the wheel. Retain the alignment mark for refitting.
• 4
  Remove the Column Shroud and Extract the Clock SpringRemove the upper and lower steering column shroud panels. Disconnect all clock spring connectors — squib, horn, and any multi-function switch connectors depending on variant. Unclip and withdraw the clock spring from the column. Do not rotate the clock spring body once removed — it contains a ribbon conductor that must remain centred.
• 5
  Centre and Fit the Replacement Clock SpringNew clock springs are supplied with a centring pin or tab that locks the internal rotor in the mid-travel position. Fit the new unit onto the column with the centring pin still engaged. Connect all harness connectors. Refit the column shroud. Refit the steering wheel to the spline alignment mark and torque the retaining nut to the workshop manual specification. Remove the centring pin only after the steering wheel is secured.
• 6
  Refit the Airbag Module, Re-enable SRS & ClearReconnect the yellow SRS squib connector and horn connectors at the steering wheel hub. Refit the airbag module and torque the mounting bolts to specification. Reconnect the battery and refit the SRS fuse. Use MUT-III to clear B1401 and run a full SRS system check. Confirm the SRS warning light extinguishes and that no further codes are stored.

Driver Airbag Module Replacement

• 1
  Disable the SRS SystemRemove the SRS fuse and disconnect the battery negative terminal. Wait a minimum of 60 seconds before approaching the steering wheel hub or airbag module. The driver airbag is a large-volume inflator — the 60-second wait is essential to ensure the SRS capacitor is fully discharged.
• 2
  Remove the Faulty Airbag ModuleAccess the airbag module mounting bolts through the rear of the steering wheel hub. Disconnect the yellow SRS squib connector — the shorting bar engages on disconnection. Place the removed module face-up on a stable, flat surface away from the work area. Follow local regulations for disposal of pyrotechnic automotive components.
• 3
  Verify Clock Spring Squib Circuit Before Fitting the New ModuleBefore installing the replacement module, use a break-out box or squib resistance simulator at the clock spring’s steering wheel–side connector to confirm that the clock spring squib circuit reads within the correct resistance window. Fitting a new airbag module to a faulty clock spring will regenerate B1401 immediately.
• 4
  Fit the OEM Replacement Module & Re-enable SRSInstall the new OEM driver airbag module and torque all mounting bolts to the workshop manual specification. Reconnect the yellow SRS squib connector firmly until the secondary lock clicks fully into place. Refit the SRS fuse, reconnect the battery, clear B1401 with MUT-III, and confirm the SRS warning light extinguishes with no returning codes.

SRS Harness Open Circuit Repair

• 1
  Isolate the Open to the Harness SegmentWith SRS disabled and isolation testing confirming the open is in the harness between the clock spring and the SRS ECU, segment-test the squib harness using a DMM in continuity mode — with all SRS connectors fully disconnected — to identify the specific break location. Check all intermediate connectors, routing clips, and column pass-through points.
• 2
  Locate and Repair the BreakTrace the harness in the identified segment. Damage is most common at the steering column upper shroud exit point, at routing clip edges within the column, and at any connector that was disturbed during prior column or shroud repair work. 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 steering wheel, confirm the full squib circuit resistance — clock spring through to SRS ECU — is within the 2.0–3.0 Ω specification using the break-out box. Reconnect the battery and SRS fuse, clear B1401 with MUT-III, and confirm the SRS warning light extinguishes with no returning codes.

Repair Cost Estimates

Prevention & Maintenance Tips

• Always disable the SRS system before any steering wheel, clock spring, or column shroud work — the most common preventable cause of B1401 is disturbing the clock spring or squib connector without following the SRS disable procedure
• Never rotate a removed clock spring — the internal ribbon conductor has a fixed travel range; rotating the body off-centre before installation will misalign it and break the conductor on first full-lock use
• Inspect the clock spring squib circuit whenever the steering wheel is removed for any reason — use a break-out box to confirm continuity through the clock spring before refitting the airbag module
• Replace the clock spring proactively on high-mileage vehicles with frequent full-lock steering use — the internal ribbon conductor has a finite flex life and is a known wear item on Mitsubishi models
• Always clear and verify SRS codes after any steering column, horn, or wheel replacement work — an SRS warning light after unrelated column work is a common post-service issue with a straightforward cause
• Use OEM or OEM-equivalent airbag modules and clock springs only — non-standard components may present squib resistance values outside the SRS ECU calibration window

Frequently Asked Questions

Can I drive my Mitsubishi with B1401 stored?

The vehicle remains driveable, but the driver airbag stage 1 squib will not fire in a collision — meaning the driver airbag cannot deploy at all, as stage 1 is the primary firing circuit. This represents a significant occupant safety risk and in many markets a permanently illuminated SRS warning light is also a roadworthiness failure point. The fault should be diagnosed and repaired as soon as possible.

How do I know if the clock spring has failed rather than the airbag module?

The clock spring is the most likely cause of B1401 on Mitsubishi vehicles, particularly where the horn or steering wheel controls have also become intermittent — the clock spring carries all of these circuits. Isolation testing with a break-out box is the definitive method: if disconnecting the clock spring from the harness-side connector resolves the open circuit reading at the ECU, the clock spring’s internal conductor has failed. If the open persists with the clock spring disconnected, the fault is in the harness between the clock spring and the SRS ECU.

Can I test the squib circuit with my multimeter?

Not directly across the squib terminals. A standard DMM in ohms mode applied across the squib terminals is a recognised deployment hazard regardless of fault type. Use an approved SRS break-out box or squib resistance simulator for all squib circuit measurements. A standard DMM may be used in continuity mode on harness conductors only after all SRS connectors are fully disconnected with shorting bars confirmed engaged.

Will B1401 clear itself after the clock spring is replaced?

No. B1401 is stored in SRS ECU memory and must be actively cleared using MUT-III or a compatible scanner after the repair is complete. Even with a new clock spring fitted and the squib circuit reading correctly, the code and SRS warning light remain until cleared with a scan tool.

What happens if the clock spring is fitted off-centre?

A clock spring fitted with the internal rotor off-centre will reach the end of its travel before the steering wheel reaches full lock in one direction. This snaps the internal ribbon conductor, generating B1401 — and potentially additional codes for horn and steering wheel controls — shortly after repair. Always fit the replacement clock spring with the centring pin fully engaged, and remove the pin only after the steering wheel has been refitted to the correct alignment mark and the retaining nut torqued to specification.

Does the SRS ECU need replacing if B1401 returns after a new clock spring and airbag module?

Only after full circuit verification has confirmed continuity through the entire squib path — from the new airbag module through the new clock spring and harness to the SRS ECU connector pins — with resistance within the 2.0–3.0 Ω specification and no open detected at any point. Corroded or spread terminals at the SRS ECU connector are more likely than an internal ECU fault and should be carefully inspected before the ECU is condemned.

How long does a clock spring replacement typically take?

For a technician with the correct workshop manual, steering wheel puller, and SRS break-out box, clock spring replacement on most Mitsubishi models takes approximately one to two hours — the majority of that time spent on airbag module removal, steering wheel removal, column shroud disassembly, and careful refitting with centring verification. Code clearing and SRS system verification with MUT-III adds a further 15–20 minutes.

Conclusion

Mitsubishi B1401 – Front Airbag (1) Driver Squib Open Circuit is a high-severity SRS fault that disables the driver airbag stage 1 firing circuit and must be diagnosed and repaired without delay. The clock spring is the most common cause on Mitsubishi vehicles and should be the first component investigated using break-out box isolation testing. Always follow the full SRS disable procedure before approaching the steering wheel hub, use an approved break-out box to isolate the open to the clock spring, airbag module, or harness, replace faulty components with OEM parts only, and clear and verify with MUT-III.