The B0079 code indicates a body-system level circuit or signal anomaly related to occupant or restraint functions; it does not by itself prove a single failed part. SAE-classified B-codes cover body electronics and can mean different things on different makes and models, so you should treat B0079 as an electrical or network symptom to be verified with measurements. Effective diagnosis relies on confirming power, ground, reference voltages, signal integrity, and data-bus messages before replacing components or modules.
What Does B0079 Mean?
This interpretation follows SAE J2012 formatting: SAE J2012 defines the standardized DTC structure and classification, and the SAE J2012-DA digital annex publishes many standardized DTC descriptions. The B-prefix places this code in the Body system family, indicating a body electrical or signal issue rather than a guaranteed mechanical failure.
The code is shown here without a hyphen suffix (no Failure Type Byte, FTB). An FTB, if present, would be a subtype describing the specific failure mode (for example, a specific open, short, intermittent, or plausibility condition) but the base B0079 remains a body-circuit or signal-level fault. This code is distinct as a circuit/communication anomaly — it flags that a signal or message for an occupant/restraint-related function failed plausibility or integrity checks rather than simply reporting a normal-range measurement.
Quick Reference
- System: Body electrical — occupant/restraint-related signal
- Format: B-code shown without FTB; FTB would refine failure type
- Primary tests: Power, ground, reference, continuity, and network message checks
- Approach: Test-driven — confirm electrical/network health before parts replacement
- Interpretation: Varies by make/model — consult wiring diagrams and module data
Real-World Example / Field Notes
In the shop, B0079 often appears after a collision repair or when a connector has been disturbed. One common pattern is intermittent faults that clear after wiggling a connector; that points to poor pin contact or corrosion rather than an internal module fault. Another common observation is a vehicle that shows the code alongside absent or implausible messages on the vehicle network scan tool — for example, the expected message from a seat-buckle or occupant-sensing circuit is missing or flagged as implausible, suggesting wiring or bus-layer issues.
When you inspect a vehicle that reports B0079, start with connector and harness condition at the likely sensor and at the body control module or restraint control module; look for corrosion, bent pins, moisture, or physical damage. Use a multimeter to verify key reference voltages and grounds at the connector while monitoring the scanned data for presence or plausibility of the related message. If wiring and connectors test good but the message is absent or inconsistent, proceed to network-level checks and consult manufacturer wiring diagrams to determine which module(s) send or receive the related signals.
Symptoms of B0079
- Warning lamp Airbag/occupant-restraint indicator illuminated or flashing on the instrument panel.
- System disable Restraint system may report reduced functionality or a disabled airbags indicator in the driver information display.
- Intermittent fault Fault code stores and clears intermittently after key cycles or driving.
- Diagnostic data Inconsistent or implausible sensor values seen in live data or Mode $06 for occupant/seat sensors.
- Network alerts Related body control module or restraint module reports communication errors or message loss on the vehicle network.
- Plausibility fail Sensor signal not matching expected ranges or seat/occupant status conflicting with other sensors.
Common Causes of B0079
Most Common Causes
- Open, short, or high-resistance wiring in the occupant restraint sensor circuit (commonly associated with seat-occupancy or presence sensors).
- Loose or corroded connector or mating surface at seat module, sensor, or body control module input.
- Intermittent communication or message integrity issues on the body CAN (Controller Area Network) where restraint-related messages are shared.
Less Common Causes
- Aftermarket seats, seat heaters, or wiring modifications causing signal interference or altered sensor loading.
- Moisture intrusion in seat harness or module connector causing intermittent resistance changes.
- Possible internal processing or input-stage issue in a control module, only after power, ground, and wiring test good.
Diagnosis: Step-by-Step Guide
Tools: good scan tool with live data and DTC view, digital multimeter (DMM), oscilloscope (preferred for signal integrity), wiring diagram for the specific vehicle, backprobe pins or breakout connector, jumper/LED test lamp, insulated hand tools, and a basic continuity tester.
- Use the scan tool to read freeze frame and live data. Confirm B0079 is current and record related live values for occupant sensors and module status.
- Check for any stored communication faults or multiple B-codes; note whether the fault appears after key-on or during certain events to narrow timing.
- Visually inspect connectors and harness routes related to occupant/resraint sensors for damage, corrosion, or aftermarket changes. Wiggle harness while watching live data for flicker.
- With key on and system awake, backprobe the sensor signal, reference (if present), power and ground circuits with the DMM. Verify proper supply voltage and a solid ground. Document voltages and compare to expected ranges from the wiring diagram or known-good references.
- Measure continuity between sensor connector and module connector to confirm no opens; check for high resistance that can cause implausible signals.
- Use the oscilloscope to view the sensor waveform (if applicable) to verify signal shape and noise. Look for dropped messages, flatlines, excessive noise, or missing transitions that indicate signal integrity issues.
- If network messages are implicated, monitor CAN traffic with the scan tool or scope to ensure messages from the seat/occupant sensor module are present and correct timing and voltage levels are within spec.
- Repair identified wiring faults (pinned connector, corrosion, chafed wires) and retest. Clear codes and perform a functional test by cycling the key and replicating the original conditions that set the code.
- If all external wiring, power, ground, and signal tests pass but the code persists, perform a swap or bench test of the suspect sensor or seat module where feasible, following manufacturer service limits, before concluding an internal module issue.
- After repair or replacement, confirm with a full scan tool functional test and a road or occupancy simulation to ensure the fault does not return and that plausibility checks are satisfied.
Professional tip: Always base a module replacement decision on measured evidence: verify supply, ground, and signal integrity first. Use an oscilloscope to catch intermittent or noisy sensor signals that a multimeter can miss, and document your measured values before and after repairs to confirm the root cause.
Follow measured electrical findings and plausibility checks before replacing parts. Use continuity, voltage, and resistance tests, plus network message verification, to justify repairs. The guidance below assumes you already performed basic power, ground, and signal integrity checks and found an intermittent or out-of-range occupant presence signal or related body-network message. If multiple tests conflict, prioritize direct electrical measurements and repeatability under known conditions.
Possible Fixes & Repair Costs
Low cost fixes ($25–$75): clean and reseat connectors or repair chaffed wiring after finding intermittent continuity, corroded pins, or voltage drop on wiggle testing. A low-cost fix is justified when continuity is restored and measured signal voltage returns to expected idle/plausibility ranges during repeat tests. Typical cost repairs ($150–$450): replace a seat occupant sensor mat or local sensor assembly when bench resistance or live-signal tests show a persistent out-of-range value and replacement restores proper sensor readings. High cost repairs ($700–$1,500+): module replacement or extensive harness repair when external power, ground, reference, and signal tests all pass but the module records internal input-stage or processing faults. Only consider control module replacement after confirming inputs and network messages are correct and repeatable and after checking manufacturer programming or configuration requirements. Factors affecting cost: labor to access seat modules, diagnostic time for intermittent faults, price of OEM vs aftermarket parts, and whether reassembly requires calibration. Each proposed fix above is tied to a specific failing test or inspection finding to avoid unnecessary parts replacement.
Can I Still Drive With B0079?
You can often drive short distances with a non-critical occupant sensing or body-network signal fault, but check safety systems first. If the fault causes an airbag or restraint warning lamp to illuminate, avoid long or high-speed trips and get the vehicle inspected promptly. If diagnostics show only a connector issue and the system’s plausibility checks pass intermittently, limit driving until the wiring is secured; intermittent faults can change system behavior without warning. Prioritize repairs when safety-related plausibility fails.
What Happens If You Ignore B0079?
Ignoring the code can allow intermittent or progressive failures to continue and may degrade occupant detection, restraint deployment logic, or related body functions depending on the vehicle. Intermittent wiring faults can become permanent, increasing repair complexity and cost later. Prompt testing and repair reduce safety risk and prevent secondary damage from water intrusion or arcing.
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
B0079 indicates a body/occupant presence signal plausibility issue and interpretation varies by make/model; SAE J2012-DA defines the DTC structure but not every manufacturer’s component. Diagnose by measuring power, ground, reference, and signal integrity, plus checking network messages for plausibility. Repair decisions must be test-driven: clean/repair connectors for intermittent continuity, replace sensors when resistance or output is out-of-spec, and consider module replacement only after all external inputs test good. Safety systems require prompt attention.
Vehicles Commonly Affected by B0079
Commonly seen on passenger cars and SUVs from manufacturers such as Toyota, Honda, Ford, and BMW, this code is often reported because many of these vehicles use occupant detection mats or seat-integrated sensors tied into complex body control modules and Controller Area Network (CAN) messaging. Variations in sensor design and network architecture make the code’s component interpretation depend on the specific make, model, and year.
FAQ
Can I clear B0079 and see if it returns?
Yes, you can clear the code with an OBD scanner to test fault recurrence, but clearing does not fix the underlying issue. Use a scan tool to clear the code, then reproduce the conditions that first set the fault while monitoring live data and network messages. If the code returns, capture freeze-frame and live values, and perform the electrical tests (power, ground, reference, signal continuity) before replacing parts. Repeated clear-and-drive without diagnosis risks missing intermittent faults.
Is B0079 likely caused by a bad connector?
It can be. Corroded or loose connectors are a common, testable cause when you find intermittent continuity, voltage drop under load, or improved readings after reseating. Use backprobe voltage checks and wiggle tests while monitoring the signal to confirm. If reseating and cleaning yield stable, in-spec voltages and message plausibility, a connector repair is justified. If faults persist, continue to sensor and module testing.
Can a module fault set B0079?
Yes, but only after you rule out wiring and power/ground/sensor issues. If continuity, reference voltage, and signal integrity tests pass and the network shows correct message timing yet the module still logs implausible occupant data, consider a possible internal processing or input-stage issue. Confirm with repeated, documented measurements and consult manufacturer diagnostics for module-specific tests before replacing any control module.
How long does a proper diagnosis usually take?
Diagnosis time varies with symptom clarity and intermittency; a straightforward connector or sensor replacement can be diagnosed in one hour, while intermittent faults often require several hours. Expect 1–4 hours for most cases: verify power/ground, check continuity and resistance, scope the signal, and monitor network messages. Factor in additional time for bench-testing sensors or seat assemblies when needed to confirm failures.
What tests will a shop perform to confirm the cause?
A shop will perform systematic tests: verify battery voltage and ground integrity, measure reference voltages, check continuity and resistance on the occupant sensor circuit, use an oscilloscope or live-data scanner to view signal behavior under load and wiggle testing, and monitor Controller Area Network (CAN) messages for plausibility. They will only replace sensors or modules after these measurements consistently point to that specific component as the cause.