B1926 – Rear pretensioner squib (left) circuit open (Lexus)

B1926 means the rear left seat belt pretensioner circuit has an electrical open, so the Lexus ES may disable that pretensioner and turn on the airbag/SRS warning. In plain terms, the restraint system cannot trust part of the crash protection. According to Lexus factory diagnostic data, this manufacturer-specific code indicates a “Rear pretensioner squib (left) circuit open.” Treat this as safety-critical. Follow Lexus SRS depowering procedures before you touch any yellow connector or harness. Use only OEM-approved test methods around squib circuits. A generic scan tool often cannot access or clear Lexus SRS faults correctly.

B1926 Quick Answer

This code points to an open circuit in the left rear seat belt pretensioner squib circuit on a Lexus. Diagnose the wiring and connectors first, with the SRS depowered, before replacing any pretensioner.

What Does B1926 Mean?

Official definition: “Rear pretensioner squib (left) circuit open.” The SRS system in your Lexus ES logged that it cannot “see” the expected electrical load for the left rear pretensioner igniter circuit. In practice, that usually means the system will disable that pretensioner channel and keep the SRS warning light on. The rest of the SRS may still work, but you cannot assume full protection.

What the module is checking: The airbag/occupant restraint control module performs a continuous circuit integrity check on each squib loop. It looks for continuity and a plausible resistance range for the rear left pretensioner circuit. Why that matters: “Open” does not prove a bad pretensioner. It only tells you the module sees a broken path somewhere in that loop. You must confirm the open with approved methods and pinpoint whether it comes from a connector issue, harness damage, or a component fault.

Theory of Operation

Under normal conditions, the Lexus SRS ECU monitors each pretensioner squib circuit and stores the result as readiness status. The rear pretensioner sits with the rear seat belt assembly. The ECU expects a stable electrical signature through the harness and connectors. That signature lets it command deployment if a crash requires it.

For B1926, that signature disappears. An open can come from a partially unseated connector, terminal spread, corrosion, a damaged harness under the rear seat, or a failed internal connection in the pretensioner. The ECU then flags the circuit as not deployable and illuminates the SRS warning. Do not probe a squib circuit with standard meter leads. Use Lexus-approved adapters and procedures only, with the SRS fully depowered.

Symptoms

These are the most common signs tied to B1926 on a Lexus ES.

• SRS warning Airbag/seat belt warning light stays on
• Message “SRS Airbag” or restraint system warning displayed (cluster wording varies)
• No readiness SRS readiness monitors fail during inspection checks
• Stored DTC B1926 returns immediately after a correct clear attempt
• Intermittent fault Light toggles after seat movement or rear seat service
• Related codes Other pretensioner/side airbag circuit codes may accompany it
• Scan tool detail OEM-level scan tool may show the channel as “open” or “NG”

Common Causes

• Disconnected rear seat pretensioner connector (left): A partially latched SRS connector opens the squib circuit and the SRS ECU flags an open.
• Harness damage under the rear seat: Seat movement, cargo intrusion, or pinched routing can break a conductor and create an intermittent or hard open.
• Connector terminal spread or poor pin fit: Low contact force increases resistance until the SRS ECU interprets the circuit as open.
• Corrosion or contamination in the connector: Moisture or drink spills wick into terminals and block current flow through the squib loop.
• Previous interior work left the circuit disturbed: Seat cover, carpet, audio, or body repairs often stress SRS wiring and cause a hidden open.
• Incorrect component or sub-harness installed: A mismatched pretensioner, seat assembly, or intermediate harness can leave the circuit open on the Lexus ES platform.
• Failed rear pretensioner squib (left): An internal open in the pretensioner initiator can trigger the code, but only after the wiring checks good.
• SRS ECU/center airbag sensor connector issue: Poor connection at the module side can open the monitored loop and mimic a component-side fault.

Diagnosis Steps

You need a scan tool with full Lexus SRS access, OEM service information, and approved SRS depowering procedures. Use a quality DVOM for power and ground voltage-drop tests. Do not backprobe squib circuits with standard leads. Use OEM-approved adapters and methods only. Gather basic hand tools to access rear seat trim without stressing harnesses.

1. Confirm B1926 with a capable scan tool and run a full SRS code read. Record DTC status (current, history) and any companion SRS codes. Save freeze frame data if available, and focus on battery voltage, ignition state, and the exact moment the SRS ECU logged the open. Freeze frame shows conditions when the fault set, while a scan-tool snapshot helps you capture an intermittent drop during a wiggle test.
2. Before any meter work, follow Lexus SRS depowering steps and wait the specified time. Then perform a visual inspection along the full circuit path you can access without unplugging squib connectors. Look for crushed wiring under the rear seat, signs of liquid intrusion, aftermarket add-ons, and any connector that looks partially seated.
3. Check fuses and power distribution that feed the SRS system. Verify the correct fuses show proper supply on both sides with the circuit loaded. Do not assume a good fuse from appearance alone. Power feed issues can cause multiple SRS faults and confuse the diagnosis.
4. Verify SRS ECU power and ground integrity with voltage-drop testing under load. Measure ground drop with the system powered and commanded awake, and keep drop under 0.1V while operating. Then check the power side for excessive drop across feed paths. This step finds high-resistance faults that continuity tests miss.
5. With SRS safely depowered, inspect the rear pretensioner (left) connector area closely. Confirm connector locks, secondary locks, and CPA devices seat fully. Check for bent terminals, pushed-out pins, terminal spread, or corrosion. Correct any fitment issues before you move deeper.
6. Use OEM-approved SRS test methods to isolate wiring versus component. On many Lexus systems, service information specifies an approved simulator or special service tool in place of the pretensioner. Follow that exact method. Do not substitute resistors or improvised loads. If the simulator makes the code change behavior, the harness and module logic likely function and the issue points toward the pretensioner or its immediate connector.
7. Test the harness section for an open without probing the squib directly. Use the OEM breakout or intermediate connector locations specified in service information. Verify continuity end-to-end on the correct pair and confirm the wiring does not short to ground or power. Flex the harness gently during testing to expose an intermittent open near the seat frame or under-seat routing.
8. Inspect the SRS ECU (center airbag sensor) connectors and related harness routing if the rear-seat side checks good. Look for prior repairs, water entry, and terminal tension issues. Reseat connectors using correct handling and verify all locks engage. Avoid forcing connectors, since terminal damage can create new faults.
9. Reassemble connectors, restore the vehicle to a safe condition, and repower the SRS system per Lexus procedure. Clear DTCs only after you correct the suspected cause. Cycle ignition and recheck for immediate return. A hard open on a continuously monitored circuit often returns at key-on if the fault remains.
10. Confirm the repair with a final scan. Ensure B1926 stays cleared and no related SRS codes reset. If the customer reported an intermittent condition, capture a scan-tool snapshot during a controlled drive or vibration input. Use that snapshot to prove the circuit stays stable under real movement.

Professional tip: Treat B1926 as a “suspected area,” not a condemned pretensioner. The most expensive mistakes happen when techs skip connector pin-fit checks and voltage-drop testing. On Lexus SRS circuits, a barely backed-out terminal can pass a quick glance. It will still set an open as the seat flexes.

Possible Fixes

• Reseat and lock the rear pretensioner (left) connector: Correct a partial engagement, restore secondary locks, and confirm the connector strain relief supports the harness.
• Repair harness damage under the rear seat: Restore conductor integrity and routing, then secure the loom away from seat tracks and sharp edges using OEM-approved methods.
• Clean and correct terminal fit: Remove corrosion and address terminal spread or pushed-out pins, replacing terminals or connector housings as required.
• Replace the rear pretensioner (left) only after circuit verification: If the harness and connectors test good with OEM-approved checks, replace the pretensioner per Lexus procedures.
• Repair SRS ECU-side connector or wiring issues: Correct high-resistance or poor pin fit at the module side when testing proves the open originates there.
• Restore correct parts configuration: Correct mismatched seat/pretensioner/sub-harness installations that leave the squib loop open on the Lexus ES.

Can I Still Drive With B1926?

You can usually drive a Lexus ES with B1926 without an engine or transmission drivability change. Do not treat it as “safe to ignore.” This DTC points to an open circuit in the left rear pretensioner squib, which belongs to the SRS system. When the SRS ECU sees this fault, it can disable that pretensioner and may limit other SRS functions, depending on Lexus platform logic. Seat belt pre-tensioning in a crash may not occur on that seating position. Do not probe SRS connectors with standard test leads. Follow Lexus depowering procedures before any inspection near yellow SRS wiring.

How Serious Is This Code?

B1926 is serious because it involves a squib circuit, not a comfort feature. In normal driving, you may notice only an SRS warning light and stored history codes. In a collision, the left rear pretensioner may not fire if the circuit stays open. That creates a real occupant protection risk. Treat the SRS system as potentially compromised until you confirm the root cause and restore normal self-checks. Diagnosis requires a scan tool with full SRS access and OEM-approved test methods. If you do not have SRS training and proper equipment, do not DIY this repair.

Common Misdiagnoses

Technicians often replace the rear seat belt pretensioner immediately because the description names the squib. That wastes time when the real fault sits in a connector or harness. The most common miss involves connector handling under the seat or at the rear seatback. High resistance or partial terminal spread can look like an open to the SRS ECU. Another frequent error involves using a regular ohmmeter across a squib circuit. That can damage components and violates OEM test guidance. Avoid guesswork by verifying connector integrity, terminal tension, and harness continuity using Lexus-approved procedures and the correct break-out tools or adapters.

Most Likely Fix

The most frequently confirmed repair path for B1926 on Lexus platforms involves correcting an open in the left rear pretensioner circuit at a connector or in the harness near the seat belt/seat frame transition. A careful inspection often finds a partially unseated connector, corrosion from moisture intrusion, or a stressed wire where the harness flexes. Only after you depower SRS and verify the circuit with OEM-approved methods should you consider replacing a pretensioner or a short sub-harness. Confirm the repair by running an SRS self-check and re-scanning after a complete key cycle sequence per service information.

Repair Costs

SRS/airbag repair costs vary significantly by component. Diagnosis must be performed by a qualified technician with SRS-capable equipment. Do not attempt airbag system repairs without proper training and safety procedures.

Last updated: April 3, 2026