B1981 – Pop up hood squib (right) circuit open (Lexus)

B1981 means the Lexus ES has a safety system fault that can disable the pop-up hood feature. In real use, you may only notice a warning light and a stored SRS/PCS-related code, but the vehicle may not provide full pedestrian-protection performance in a front impact. According to Lexus factory diagnostic data, this manufacturer-specific code indicates an open circuit in the right pop up hood squib circuit. Treat this as safety-critical. Depower the SRS and follow OEM handling steps before you touch any related connector. Use only OEM-approved test methods for squib circuits.

B1981 Quick Answer

B1981 on Lexus indicates the right pop up hood squib circuit shows an open circuit condition. The control unit cannot see the expected circuit integrity, so it flags the pedestrian protection actuator circuit as faulty.

What Does B1981 Mean?

Official definition: “Pop up hood squib (right) circuit open.” In plain terms, the Lexus ES control unit that monitors pedestrian protection detects a broken electrical path to the right-side hood pop-up squib. That matters because the system needs confirmed circuit continuity before it will arm and operate correctly.

What the module checks: the controller performs an integrity check of the squib circuit through its harness and connectors. It looks for a valid electrical load and a stable circuit state. Why that matters for diagnosis: the code points to a suspected open in wiring, connectors, or the squib path. It does not prove the squib itself failed. Confirm the circuit and connector condition with OEM-approved procedures before you replace anything.

Theory of Operation

On Lexus vehicles equipped with a pop-up hood, the system uses dedicated actuators and “squibs” to raise the hood during certain impacts. The controller monitors each squib circuit at all times. It uses that circuit check to decide if the system can arm safely.

An “open circuit” occurs when the controller cannot complete its continuity check. A loose connector, terminal spread, corrosion, or harness damage can break the path. Improper probing can also damage terminals and create an open. Because this circuit relates to a pyrotechnic device, Lexus requires SRS depowering and approved test adapters before any hands-on circuit work.

Symptoms

These are the most common signs technicians and owners see with B1981 on a Lexus ES.

• Warning light SRS/airbag warning light on, and possibly a pedestrian-protection or PCS message depending on platform
• Stored DTC B1981 present as current or history in the related control unit memory
• System disabled Pop-up hood system shows disabled or “check system” status in the vehicle information display on some configurations
• No deployment readiness Controller reports a faulted right squib circuit, so it will not arm that output
• Intermittent behavior Warning appears after bumps, hood service, or temperature swings when a connector sits on the edge of contact
• Scan data clues Related data may show “open” or “NG” for the right squib circuit check (wording varies by Lexus scan software)
• Other related codes Additional pedestrian protection or SRS circuit codes may appear if the harness damage affects multiple paths

Common Causes

• Disconnected squib connector at the right pop-up hood actuator: A partially latched SRS connector opens the circuit and the module detects no continuity through the squib.
• Terminal spread or poor pin fit in an SRS connector: Low contact force creates an open under vibration even when the connector looks seated.
• Harness damage in the front-end/hood hinge area: Repeated flexing, prior collision repair, or pinch points break the conductor inside the insulation.
• Corrosion or liquid intrusion at an in-line connector: Oxidation increases resistance until the circuit goes open to the module’s monitoring current.
• Aftermarket repairs or splices in the SRS-related harness: Improper crimping or solder wicking can crack the conductor and create an intermittent open.
• Right pop-up hood squib/actuator internal open: The initiator element or internal connection can open, so the module cannot “see” the expected load.
• Connector CPA/lock missing or not engaged: Without the secondary lock, the terminals can back out and open the circuit during normal driving.
• Incorrect parts or connector mismatch after body work: A wrong actuator or sub-harness can prevent full terminal engagement and leave the circuit open.

Diagnosis Steps

Use a scan tool with full Lexus SRS access and a wiring diagram for the pop-up hood (active hood) system. You also need a DVOM for power and ground voltage-drop tests, plus OEM-approved SRS test adapters or a breakout method specified by Lexus. Do not back-probe or ohm-check squib circuits with standard leads. Depower the SRS system using Lexus procedures before touching any SRS connector.

1. Confirm DTC B1981 with a capable scan tool and record all SRS codes. Save freeze frame data. Focus on battery voltage, ignition state, vehicle speed, and any related active hood or front impact sensor DTCs. Freeze frame shows conditions when the fault set. A scan-tool snapshot helps catch an intermittent open during a wiggle test. Do not clear codes as a diagnostic step.
2. Perform a quick visual inspection of the right pop-up hood squib circuit path before meter work. Look for recent front-end repairs, hood hinge harness routing issues, missing connector locks, and damaged loom near the latch support and radiator support. Verify the right actuator connector sits fully seated and locked. Stop and depower the SRS system before you disconnect anything.
3. Check fuses and power distribution that feed the SRS/airbag system and any active hood control circuitry used on the Lexus ES platform. Use the wiring diagram to identify the exact fuse locations for this vehicle. Test fuses with a load, not only a visual check. A fuse can crack and pass a continuity test but fail under load.
4. Verify module power and ground integrity under load. Keep the circuit operating when possible and run voltage-drop tests. Measure battery positive to the module power feed, then module ground to battery negative. Accept less than 0.1 V drop on grounds with the circuit active. A weak ground can mimic an open-load fault by collapsing monitoring current.
5. Depower the SRS system using OEM steps and the required wait time before disconnecting SRS connectors. Confirm the system remains depowered. Follow Lexus handling rules for SRS connectors, CPA locks, and shorting bars. Never use a test light on SRS circuits. Do not probe squib terminals with standard meter tips.
6. Inspect the right pop-up hood squib connector and terminals closely. Check for pushed-out pins, terminal spread, corrosion, or signs of prior probing. Verify the secondary lock engages and the connector body has no cracks. Compare pin fit to the opposite side only if the vehicle uses a matching design. Do not swap components to “see if the code moves.”
7. Inspect the harness from the right actuator back toward the SRS-related control unit junctions. Focus on pinch points, sharp brackets, and areas disturbed by collision repair. Gently tug-test the harness near strain reliefs. If you find damaged wiring, open the loom and inspect individual conductors. Repair using OEM-approved methods for SRS-related wiring.
8. Perform OEM-approved circuit integrity checks without directly measuring squib resistance using generic methods. Use Lexus-approved breakout adapters and follow service information for “open circuit” verification. Test the continuity of each wire segment end-to-end with the squib disconnected, if the procedure allows. Also check for short to ground and short to power on each circuit leg. An open on either leg can set B1981.
9. If the wiring passes, verify the actuator/squib side using the Lexus test procedure for the pop-up hood squib. Many Lexus systems require a dedicated SRS check tool or specified resistor substitute at the harness side. Only use the value and method listed by Lexus. This step helps separate a harness open from an internal open in the right actuator/squib assembly.
10. Reassemble connectors with CPAs fully locked and restore SRS power per Lexus procedure. Run a self-check and rescan for codes. If B1981 returns immediately at key-on, treat it as a hard fault and recheck connector seating and circuit integrity at the last disturbed point. If it does not return, perform a controlled road test and use a scan-tool snapshot while gently stressing the harness routing areas.
11. Confirm the repair with a final scan and verify no related SRS/active hood codes remain. Document the fix and the exact root cause. Make sure the harness routing matches OEM clips and strain reliefs. A correct routing prevents the same open from returning after a few hood cycles.

Professional tip: Many “circuit open” SRS faults on Lexus active hood systems trace back to connector lock issues after body work. Treat every orange or SRS-identified connector as a precision connection. If you do not use the OEM-approved adapters and depowering steps, you can create a new fault or trigger deployment risk. Verify power and ground voltage drops first, then chase the open with the proper test method.

Possible Fixes

• Reseat and lock the right pop-up hood squib connector: Fully engage the connector and secondary lock, then verify the code does not reset.
• Repair harness damage in the right active hood actuator circuit: Restore conductor integrity and routing using Lexus-approved SRS wiring practices.
• Clean and correct terminal fit issues: Address corrosion, pin tension, or pushed-out terminals, then confirm stable contact under vibration.
• Replace the right pop-up hood actuator/squib only after circuit verification: Replace the unit if OEM testing proves an internal open and the harness tests good.
• Correct prior repair workmanship: Remove improper splices or wrong connectors and return the circuit to OEM configuration.

Can I Still Drive With B1981?

You can usually drive the Lexus ES with B1981 present, but you should treat it as a safety-critical fault. This code points to an open circuit in the right pop up hood squib. That squib forms part of the pedestrian protection system, and it shares diagnostics and safety rules with the SRS network on many Lexus platforms. Driving does not typically change engine performance, but it can leave the pop-up hood function unavailable in a collision event. Do not attempt DIY probing or connector checks around squib circuits. Depower the SRS using OEM procedures before any inspection, and use an SRS-capable scan tool for diagnosis and verification.

How Serious Is This Code?

B1981 is serious because it involves a squib circuit and “circuit open” equals lost control of a pyrotechnic load. In day-to-day use, the vehicle may feel normal. The issue often looks like an inconvenience because it mainly triggers warning indicators and stored faults. In an impact, however, the system may not deploy the pop-up hood on the right side. Treat the overall SRS system as potentially compromised until you confirm the root cause. Proper diagnosis requires SRS-certified equipment, OEM-approved test methods, and technician training. Do not substitute test lights, back-probing, or resistance checks with standard leads on squib wiring.

Common Misdiagnoses

Technicians often replace the right squib or hood actuator assembly first because the DTC “names” the component. That skips the actual failure mode, which is an open in the circuit. Another common error involves checking resistance directly across squib circuits with a standard meter. That can trigger damage or create unsafe conditions. Shops also misread intermittent opens caused by connector seating, water intrusion, or harness strain near the hood hinges. Avoid wasted spending by verifying the circuit path end-to-end with OEM procedures, using the correct simulator tools or approved measurement points, and confirming the module sees a stable circuit state.

Most Likely Fix

The most frequent confirmed repair direction involves correcting an open circuit in the right pop up hood squib wiring path, not replacing control modules. Focus first on connector engagement, terminal fit, and harness damage in the front-end/hood routing where movement and moisture stress the loom. If the wiring and connectors test good using OEM-approved methods, then suspect a failed right squib/actuator assembly or an internal open in the component. After repairs, run a full SRS scan and confirm the code stays cleared during the conditions Lexus uses to re-check that circuit. Those enable conditions vary by platform.

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