B0071 is a Body-class Diagnostic Trouble Code that signals an abnormal condition in a restraint-related or occupant-detection circuit reported by the vehicle’s body electronics. This code describes a system-level fault type — a circuit, signal, or plausibility condition — and does not by itself identify a single failed part. Interpretation can change by make, model, and year because manufacturers map body functions differently. You should treat B0071 as a pointer to a circuit or signal anomaly that requires electrical and network verification before replacing sensors or modules.
What Does B0071 Mean?
This guide follows SAE J2012 formatting: SAE J2012 defines DTC structure and provides standardized descriptor text, and the SAE J2012-DA digital annex publishes the formal DTC descriptions used by many manufacturers. B0071 is shown here without a hyphen suffix (no Failure Type Byte or FTB). If an FTB were present (for example “-1A”), it would identify a subtype or specific failure-mode variant tied to that base code.
There is no single universal component-level definition for many B-codes, including B0071; interpretation varies by vehicle. What makes B0071 distinct is that it designates a body-system signal or circuit reporting an abnormal condition (electrical fault, implausible signal, or communication/processing anomaly) related to occupant detection or restraint sensing rather than a confirmed hardware break.
Put simply, when you see B0071 it means the vehicle’s body electronics noticed a restraint-related input that doesn’t look right — a value out of range, a missing reference, or a corrupted network message — and flagged it as a safety-related plausibility or circuit fault. Because of that, your diagnostic process should focus on signals, voltage references, grounds, connectors, and network traffic before you assume any single replaceable component is at fault.
Quick Reference
- System: Body-class circuit related to occupant detection or restraint sensing
- Typical symptom: Occupant/airbag warning lamp, seat-belt/airbag behavior anomalies
- Primary approach: Test power, ground, reference, signal integrity, and network messages
- Severity: Safety-related; diagnose promptly before normal operation
- Interpretation varies by make/model — confirm with vehicle-specific tests
- Tools you’ll likely need: scan tool with live data, DMM, wiring diagrams, backprobe pins, and optionally an oscilloscope
Real-World Example / Field Notes
In workshop practice you’ll often see B0071 stored after body modules report an out-of-range or missing signal from a seat occupancy sensor mat or seatbelt latch sensor. On some vehicles the body electronics record this when a seat mat returns an implausible resistance or capacitance reading, or when a module receives a corrupted data packet that fails plausibility checks. These are examples of commonly associated causes, not guaranteed definitions.
For example, a technician might scan a 2015 midsize sedan and find B0071 accompanied by a seat-occupied flag that flickers in the live-data stream when a passenger shifts position. Wiggle-testing the harness under the seat reproduces the flicker and the code returns. In contrast, another case could involve a luxury SUV where B0071 appears without any change in live-data; an extended diagnostic reveals that the airbag control module intermittently loses its reference voltage during cold cranking due to a weak ground strap.
Typical field checks that narrow the fault quickly are simple: scan the network for related live data, record whether the fault is active or historic, and check for additional stored body or airbag domain faults. An active B0071 tied to intermittent symptoms often points to a wiring or connector issue; a persistent, unchanging fault after wiggle-testing may indicate a sensor or mat problem when verified by measurements.
Workshop notes: measure mat circuit resistance or capacitance against known-good readings when available, and watch the sensor waveform with an oscilloscope if the module exposes a pulsed signal. Also confirm vehicle reference voltage and ground stability while cycling the circuit; many false occupant-detection faults trace back to weak grounds or contaminated connectors. Keep a record of values you measure so you can compare before/after repairs and justify parts replacement by evidence rather than guesswork.
Symptoms of B0071
- SRS lamp Illuminated or flashing on the dash indicating a stored restraint system fault.
- Warning memory One or more restraint-related fault codes stored in the diagnostic memory.
- Intermittent Lamp behavior that changes with vehicle vibration, seating position, or connector movement.
- Icon persistence SRS warning stays on after key cycles and does not clear with normal driving.
- Service messages In some vehicles, a supplemental message (e.g., “Service Airbag”) appears in the cluster.
- Plausibility Related systems (seatbelt pretensioner, occupancy detection) show inconsistent behavior or incorrect seat-occupied status.
- Secondary symptoms you may notice: seatbelt reminder chimes when seat is unoccupied, or passenger airbag status shows “off” when occupied.
Common Causes of B0071
Most Common Causes
- Loose, corroded, or pushed-back connector at a restraint harness commonly associated with seat or airbag module circuits.
- Broken or high-resistance wiring in the occupant restraint harness due to seat movement or prior repairs.
- Poor or missing power or ground supply to restraint sensors or pretensioner circuits.
- Intermittent contact in multi-pin connectors that affects the restraint circuit signal integrity.
- Aftermarket seat heaters, audio equipment, or seat swaps that disturb the original harness routing and stress wires under the seat.
Less Common Causes
- Faulty seat-occupancy sensor module or mat sensor (one possible cause depending on vehicle).
- Control module input-stage issue after all external power, ground, and wiring tests pass.
- CAN (Controller Area Network) message timeout or corruption affecting restraint status reporting.
- Water intrusion or prior collision damage causing hidden wiring faults.
- Battery disconnects and partial resets that leave modules in an undefined state; some vehicles need a prescribed reinitialization or calibration after power loss.
Diagnosis: Step-by-Step Guide
Tools: diagnostic scan tool with live data and DTC capability, digital multimeter, oscilloscope (optional), wiring diagrams/service manual, backprobe pins, small inspection mirror, contact cleaner, and a wiggle test tool or insulated probe. Use Safety gloves and disconnect battery per vehicle procedures before connector repairs.
- Record the freeze frame and stored fault description with your scan tool and note whether the code is permanent or pending. Save screenshots or export logs if your tool allows it; this helps later verification.
- Visually inspect seat rails, connectors under the seat, and airbag module connectors for corrosion, bent pins, or disconnected plugs. Pay attention to hidden short runs where the harness rubs against metal or plastic and to clips that may have been removed during seat service.
- With ignition on, verify battery voltage at the restraint system power feed and check a known good ground for low resistance (<0.5 Ω) to chassis. Many manufacturers expect a stable 12 V reference within a narrow tolerance; large drops under load are a red flag.
- Backprobe the module or sensor signal and reference pins while watching live data; look for expected voltages or switching behavior per vehicle data. If the seat-occupied flag toggles while you wiggle the harness, you’ve identified an intermittent wiring problem.
- Perform a continuity and resistance check of suspect harness sections (seat harness to module); check for high resistance or intermittent opens using a wiggle test while monitoring continuity. Be mindful of airbag squib circuits — follow manufacturer safety protocols and never apply more than recommended test voltages to pyrotechnic devices.
- If available, use an oscilloscope to confirm signal integrity (clean square/analog waveform) and to catch intermittent noise or dropouts not visible with a DMM. Oscilloscope traces often reveal noise injected by a bad ground or a partially shorted conductor that a meter will miss.
- Inspect and clean connector terminals with contact cleaner, reseat firmly, then clear the code and re-test for reappearance under normal and wiggled conditions. Use dielectric grease on pin terminals where recommended to prevent future corrosion.
- If wiring, connectors, power, and ground test good, compare module inputs and outputs to manufacturer reference; if divergent, consider a possible internal processing or input-stage issue after verification. Document all measurements to support requesting a module bench test or replacement authorization if needed.
- Use stored data (Mode 06/monitoring) where available to check sensor channel plausibility and resistance ranges against spec values. Mode 06 can help you find out-of-range ADC counts or rapidly fluctuating channels that correlate to B0071.
- After repairs, perform a full system scan, reinitialize any required calibrations per manufacturer procedures, and confirm the SRS lamp stays off across several ignition cycles. Some vehicles require a specific “seat calibration” or occupant sensor learn procedure to be run with a dealer or manufacturer-level tool.
Professional tip: Always confirm external wiring, power, and ground before replacing a module. Use a controlled wiggle test and repeat DTC clearing to reproduce intermittent faults—most B0071 cases are fixed by repairing a poor connector or harness chafe rather than swapping modules.
Possible Fixes & Repair Costs
Low costs typically cover simple repairs backed by clear test results: cleaning a corroded connector, reseating a harness, or repairing a broken terminal when continuity and voltage checks show an open or intermittent connection. Typical repairs include replacing a damaged wiring section, replacing a seat occupant sensor or squib connector after bench or oscilloscope verification of bad signal integrity, and calibrating sensors when plausibility tests fail. High-cost scenarios involve module replacement or dealer-level calibration, but only after power, ground, input signals, and bus communication have been proven good with a multimeter and scope.
Cost is influenced by parts, labor time, diagnostic effort, and whether dealer-level programming is required. Labor rates vary widely; a simple connector clean could be a 30–60 minute job while a module replacement and relearn can take several hours and require dealer tooling.
- Low: $50–$250 — justified by failed continuity, visible corrosion, or a contaminated connector fixed on-bench. This typically includes basic labor and small parts like terminals or clips.
- Typical: $250–$900 — justified by a verified sensor or harness replacement after an oscilloscope shows poor waveform or Mode 06 shows out-of-range values. This covers replacement occupant mats, seat harness assemblies, or single-sensor modules with moderate labor.
- High: $900–$2,500+ — justified when replacement of an airbag control module or dealer programming is required after all external inputs test good and communication checks pass. OEM modules, reprogramming fees, and multiple calibrations push costs toward the high end.
Examples: If you replace a seat occupancy mat, parts alone can range from $150–$600 depending on seat complexity and whether the mat includes heating elements. An airbag control module can cost $500–$1,800 as a part, and dealer programming can add $150–$500 to total cost. If a harness runs through the seat and requires removal and reassembly, expect at least 1–3 hours of labor in most shops.
Can I Still Drive With B0071?
You can often drive short distances with this code present, but it depends on what the code represents on your vehicle. Because B0071 is related to the occupant restraint/airbag circuit, safety systems such as Supplemental Restraint System (SRS) may be limited or disabled. Drive only if necessary and carefully; avoid long trips. Confirm system readiness with a scan tool and perform basic power, ground, and communication checks before relying on the vehicle in everyday driving.
If your vehicle shows a persistent SRS light, you should treat it as an unsafe condition. Some cars will disable passenger airbags when occupancy detection malfunctions, which could be hazardous in a crash if a passenger is present. If you must drive, keep speeds moderate and avoid risky situations until the fault is resolved.
What Happens If You Ignore B0071?
Ignoring B0071 can leave the airbag or occupant-sensing systems degraded or disabled, increasing risk during a crash and possibly preventing proper deployment. It may also prevent the vehicle from passing inspection in regions that check SRS readiness. Intermittent wiring faults can worsen over time and lead to higher repair costs.
In addition, unresolved electrical faults can lead to cascading issues: a shorted harness can eventually trip other modules, and water intrusion at a seat connector can corrode pins and spread to neighboring circuits. From both a safety and cost perspective, delaying diagnosis invites risk and potentially larger repair bills later.
Related Codes
- B0019 – Occupant Restraint Airbag Circuit Fault
- B0018 – Body Circuit Fault — Restraint Sensor Signal
- B0017 – Body Circuit Signal Integrity Fault
- B0016 – Occupant Sensing Circuit Fault (SRS)
- B0014 – Occupant Restraint Circuit Fault
- B0011 – Occupant Restraint Circuit Fault
- B0009 – Restraint System Circuit Fault
- B0008 – Supplemental Restraint System Circuit High
- B0007 – Supplemental Restraint System Circuit Fault
- B0006 – Restraint Deployment Commanded Too Long
Key Takeaways
- System-level code: B0071 indicates an occupant restraint or airbag circuit fault; interpretation varies by make/model.
- Test first: Use continuity, voltage, and waveform tests before replacing parts.
- Module caution: Suspect internal module issues only after all external wiring, power, ground, and signal tests pass.
- Safety impact: The fault can affect airbag deployment or occupant classification—address promptly.
- Documentation: Record your measurements and test results to ensure correct parts are replaced and to support warranty claims.
Vehicles Commonly Affected by B0071
B0071 is frequently reported on vehicles from manufacturers with advanced occupant classification or multiple-seat sensors, commonly seen on some Toyota, Ford, and General Motors vehicles. These platforms often use seat-occupancy sensors, multiple squibs, and complex body network integration, increasing the number of circuits and connectors where corrosion, harness damage, or sensor plausibility issues can show up as this B-code. Interpretation still varies by make, model, and year.
Because vehicle designs evolve, later-model cars with heated seats, powered seats, and integrated sensors increase the chances of wiring chafe or connector wear. If you own a vehicle with seat removal history (upholstery work, aftermarket installs, collision repairs), tell the technician — prior seat service is a common root cause.
FAQ
Can I clear B0071 with a code reader and drive normally?
Clearing the code will turn off the warning temporarily but does not fix the underlying electrical problem. If the fault is intermittent, the code may return. You should perform basic checks: verify battery voltage, test power and ground at the restraint module, and check continuity of related harnesses. Only after tests confirm valid signals and no intermittent opens should you consider the issue resolved for safe driving.
Can a bad connector cause B0071 without a failed sensor?
Yes. Corroded or loose connectors can cause high resistance, intermittent contact, or signal dropouts that trigger B0071. A multimeter continuity test or wiggle test while monitoring live data or diagnostic frames will show if the connector is the problem. If the connector or terminal repairs restore normal voltage and signal integrity, replacing the sensor is not necessary.
Is module replacement usually required for this code?
Module replacement is not usually the first step. Only consider possible internal processing or input-stage issues after thorough external testing—power, ground, reference voltages, CAN/bus communication, and input signal integrity all test good with a scope and scan tool. If those tests pass and the fault persists, module replacement or dealer-level repair may be justified.
What diagnostic tests should a shop perform first?
A shop should begin with a full read of fault data and freeze frame, check battery and charging voltages, verify power and ground at the restraint module, and perform continuity checks on relevant harnesses. Next use an oscilloscope or scope-enabled scan tool to confirm sensor waveforms and plausibility. Repair decisions must be based on failed tests, not part replacement guesses.
How long will a proper repair take and what affects time?
Simple connector repairs or harness splices can take under an hour. Sensor replacement and calibration may take 1–3 hours. Module diagnostics, bench testing, and dealer programming increase time significantly. Diagnostic time is driven by accessibility, how intermittent the fault is, and whether in-vehicle or bench testing is required to reproduce the issue and confirm a successful repair.
Factors that add time: removing seats to access connectors, waiting for dealer diagnostics or replacement parts, and performing required learn procedures. If the fault is intermittent, expect diagnostic time to increase because you need to reproduce the failure under test conditions.