B1807 – Passenger squib circuit short to ground (Toyota)

Toyota-specific code — factory diagnostic data

B1807 means the airbag system has detected a fault that can disable the front passenger airbag. In real use, you will see the SRS airbag warning light, and the system may not protect a passenger as designed. This is a Toyota manufacturer-specific code, so Toyota’s definition controls the diagnosis on a C-HR. According to Toyota factory diagnostic data, B1807 indicates a “Passenger squib circuit short to ground.” That wording points to the airbag inflator firing circuit for the passenger side. Treat this as safety-critical and follow Toyota SRS depowering steps before touching related wiring.

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B1807 Quick Answer

B1807 on Toyota vehicles means the SRS airbag module sees the passenger squib (inflator) circuit pulled to ground. The most common root cause is a wiring or connector fault, not the airbag module.

What Does B1807 Mean?

Official definition: “Passenger squib circuit short to ground.” The SRS airbag module has detected a ground short in the circuit used to deploy the front passenger airbag inflator. In practice, the module turns on the SRS warning light and may disable that deployment output to prevent an unintended event.

What the module checks and why it matters: The SRS airbag module monitors the squib circuit for electrical integrity. It looks for an abnormal low-resistance path to chassis ground on the driver stage and harness path to the passenger inflator. A short-to-ground finding does not prove the inflator failed. It tells you the module measured a circuit condition outside its expected window. That distinction matters because correct diagnosis focuses on connector condition, harness routing, and approved SRS test methods before any part replacement.

Theory of Operation

Under normal operation, Toyota’s SRS airbag module continuously monitors each deployment loop. The “squib” refers to the igniter inside the inflator. The module uses internal diagnostics to verify the circuit remains intact and isolated from ground. It also uses dedicated shorting bars in SRS connectors to reduce accidental deployment risk when disconnected.

B1807 sets when the module detects the passenger squib circuit has an unintended path to ground. Damaged insulation, pinched wiring, moisture in a connector, or a mis-seated connector can create that path. A shorted driver stage inside the module can also pull the circuit low, but you only consider that after you verify the harness and components with Toyota-approved procedures.

Symptoms

You will usually notice an SRS warning first, then confirm the code with a scan tool that can access Toyota SRS data.

• SRS light illuminated and stays on after key-on
• Passenger airbag may disable or report a fault status in scan data
• Message “Check SRS/Airbag” on the cluster (varies by Toyota platform)
• Stored DTC B1807 present in the SRS airbag module memory
• Intermittent warning that changes with seat movement or harness movement
• Freeze frame or snapshot data showing the fault occurred during vibration or a recent interior repair
• Code reset fails or the code returns immediately after a proper clear with an SRS-capable scan tool

Common Causes

• Harness chafe to body ground: The passenger squib wires can rub through insulation and touch metal, creating a hard short to ground that the SRS airbag module flags.
• Connector damage at the passenger airbag circuit: Bent terminals, broken locks, or cracked housings can let a terminal contact the shell or ground path and pull the circuit low.
• Corrosion or moisture intrusion in SRS connectors: Water tracks and corrosion products can bridge terminals to ground and mimic a direct short.
• Incorrect probing or test equipment use: Standard test leads, back-probing, or powered test lights can deform terminals or introduce a ground path on a sensitive squib circuit.
• Previous interior or dash work disturbed the SRS harness: Aftermarket accessories or dash removal can pinch the harness and short the squib circuit to a bracket or reinforcement.
• Shorted component in the passenger airbag module circuit: A fault inside the passenger airbag (squib) assembly or an intermediate connection can present as low resistance to ground, depending on Toyota platform design.
• Improper connector engagement: A partially seated connector can misalign terminals and create an unintended contact to ground inside the connector body.
• SRS airbag module internal driver fault: An internal low-side driver or sensing circuit fault can report a short-to-ground condition, but you must prove wiring integrity first.

Diagnosis Steps

You need a scan tool with full Toyota SRS access, plus OEM-approved SRS depowering procedures. Use a quality DMM with a low-amp capability only where Toyota allows it, and use approved breakout leads or adapters. Do not probe squib connectors with standard meter tips. Have wiring diagrams and connector views for the Toyota C-HR platform you service.

1. Confirm the DTC and capture evidence: Perform a full SRS scan and record B1807 as pending, stored, or history. Save freeze frame data if available. For this circuit DTC, focus on battery voltage, ignition state, and any companion SRS codes that point to the same branch.
2. Depower the SRS and do a targeted visual inspection first: Follow Toyota’s SRS disable procedure before touching any SRS connectors. Inspect the passenger squib circuit routing, looking for pinched loom, rubbed-through tape, or contact with sharp brackets. Pay attention to areas disturbed during glovebox, radio, or dash work on the C-HR.
3. Check fuses and power distribution before any ECU measurements: Verify SRS-related fuses and any IG/BATT feeds that support the SRS airbag module. Use a loaded test method. A fuse can look good and fail under load.
4. Verify SRS airbag module power and ground with voltage-drop testing: Keep the system in a safe state per Toyota procedures. With the circuit operating as allowed, voltage-drop test the module grounds under load. Target less than 0.1 V drop. Confirm the module feeds do not sag under load, because a poor ground can distort circuit monitoring.
5. Inspect connector condition and terminal fit: With SRS depowered, inspect the relevant connectors along the passenger squib circuit path. Look for pushed-out terminals, spread pins, damaged CPA locks, or signs of moisture. Do not use aggressive picks. Confirm each terminal has proper retention and alignment.
6. Check for a short-to-ground in the harness using an OEM-approved method: Keep the airbag circuit isolated per Toyota instructions. Using approved breakout adapters, test the passenger squib circuit conductors for continuity to chassis ground. A true short-to-ground typically shows near-zero resistance and stays steady when you flex the harness.
7. Use a wiggle test to catch an intermittent short: Flex the harness at common pinch points and connector backshells while monitoring the short-to-ground indication. Pair this with a scan tool “snapshot” if the tool supports it. Freeze frame shows when the DTC set, while a snapshot captures the moment an intermittent short returns during your manipulation.
8. Isolate the fault by splitting the circuit at intermediate connectors: If the circuit tests shorted, disconnect intermediate junctions one at a time per wiring diagrams. Re-test each section for short-to-ground. This step locates whether the short sits in the body harness, the dash harness, or closer to the passenger airbag assembly.
9. Confirm the passenger airbag (squib) side versus wiring side: If Toyota service information allows substitution with an approved SRS load tool, use it exactly as specified to determine whether the module sees a normal load. Never use resistors or homemade loads. If the short disappears with the squib disconnected, the fault lies downstream. If it remains, the wiring or module driver circuit remains suspect.
10. Re-check for related DTCs and logic conflicts: A short-to-ground code can appear with other squib or pretensioner codes when a shared harness branch gets damaged. Resolve power/ground and harness faults first. Then re-scan to confirm only B1807 remains, if it returns at all.
11. Confirm the repair correctly: Reassemble connectors with correct seating and locks. Restore the SRS system per Toyota procedures. Clear codes with the proper scan tool, then perform a key cycle and re-scan. A hard short monitored continuously will usually reset quickly at key-on if you missed the root cause.

Professional tip: Treat B1807 as a “suspected trouble area,” not a confirmed failed airbag. Prove the short with isolation tests before any parts decision. Most wasted spending comes from replacing the passenger airbag module when the harness insulation rubbed through on a bracket near the dash beam.

Possible Fixes

• Repair harness insulation and reroute the loom: Fix the verified chafe point, restore shielding, and secure the harness away from brackets that caused the short.
• Clean, dry, and restore connector integrity: Address verified moisture intrusion, corrosion, or terminal damage, then confirm proper pin fit and lock engagement.
• Replace damaged terminals or connector housings: Install the correct Toyota repair terminals and seals when terminal-to-shell contact or poor retention caused the short.
• Correct pinched harness from prior repairs: Remove improper fasteners, clips, or accessory wiring that compressed the SRS loom into ground contact.
• Replace the passenger airbag (squib) assembly only after isolation proves it: If the short exists only on the component side and testing supports it, replace the verified faulty unit and re-check for returning codes.
• Replace the SRS airbag module only after all circuit checks pass: Consider module replacement only when power, grounds, wiring, and connector integrity test good, yet the module still reports a short-to-ground.

Can I Still Drive With B1807?

You can usually drive a Toyota C-HR with B1807, but you must treat the SRS system as compromised. The SRS airbag module sets this code when it sees a passenger squib circuit short to ground. That fault can disable the passenger airbag, affect other SRS functions, or turn the entire system off as a safety response. Driving does not typically harm the engine or transmission. The risk sits in crash protection. Do not probe SRS connectors or wiring at home. Follow Toyota depowering procedures before any inspection. Use an SRS-capable scan tool to confirm the fault type and current status before planning repairs.

How Serious Is This Code?

This code is serious because it involves a squib circuit, which directly relates to airbag deployment control. When B1807 is present, the Toyota SRS airbag system may not deploy the passenger airbag correctly in a crash. In some cases, the SRS module may disable one or more deployment stages to prevent an unintended event. You might still have normal drivability, so it can feel like an inconvenience. It is not. Treat it as a safety-critical condition. Diagnosis requires OEM-approved SRS test methods, correct depowering steps, and technician training. Avoid DIY repair attempts and avoid using generic electrical test leads on squib circuits.

Common Misdiagnoses

Technicians often replace the passenger airbag or spiral cable without proving the short to ground first. Another common mistake involves checking the circuit with a test light or standard ohmmeter through the squib path. That approach violates Toyota SRS handling rules and can damage terminals. Some shops also chase low battery voltage or unrelated body codes and miss the real issue. B1807 points to a suspected trouble area, not a failed part. Prevent wasted spending by verifying the short occurs in the harness, connector, or component side using OEM-approved adapters, and by confirming the code returns as “current” after proper SRS depowering and reconnection.

Most Likely Fix

The most frequently confirmed repair direction for B1807 on Toyota platforms is correcting a short-to-ground in the passenger squib wiring or connectors, often near a disturbed connector or harness routing point. A second common direction involves terminal damage or moisture intrusion at an SRS connector that bridges the circuit to ground. Do not assume the passenger airbag module itself failed. Prove the short with Toyota-approved procedures, then repair wiring integrity and terminal tension, and finally clear and recheck with a full-function SRS scan tool to confirm the code stays out.

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 9, 2026

Definition source: Toyota factory description · Autel MaxiSys Ultra & EV. Diagnostic guidance is based on factory-defined fault logic for this code.