Comprehensive diagnostic guide for OBD-II code B0155 Body category

Important Notes

• B0155 is a body (B) category diagnostic trouble code in the OBD-II system. The exact meaning of B0155 can vary by vehicle make/model and is often defined in manufacturer service information. do not include a manufacturer-specific definition for B0155, so treat this guide as a general, safety-conscious framework for a body-side airbag/seat/occupant-related fault commonly associated with B codes. For the precise factory definition, consult the vehicle's OEM service data and the GitHub definitions mapping for standard OBD-II codes.

• For standard code categorization and mapping references, GitHub definitions provide a general framework that B codes correspond to body electrical systems. Use manufacturer-specific definitions as the ultimate authority.

Symptoms

• MIL/Check Engine-type indicator specifically for the airbag/SRS light (SRS) is on and stored as a B0155.
• SRS warning light remains illuminated after vehicle startup or intermittently flashes.
• Symptoms of an airbag/pretensioner system fault, which may include:
  • Airbag warning light on with related B codes in the SRS subsystem.
  • Occupant classification system (if applicable) or pretensioner circuit fault indicators.
• Potential absence of obvious drivability symptoms; the fault is primarily safety-critical and system protection related.

What B0155 typically relates to (conceptual, per standard code practice)

• B codes generally cover body electrical systems, including airbags, seat belts/pretensioners, occupant sensors, and related wiring.
• The exact fault described by B0155 is manufacturer-specific. Common themes in B0155-like body-airbag/pretensioner faults involve harness/connectors, clock spring integrity, airbag module (SRS control unit) reliability, or seat/occupant sensor circuits.

Diagnostic Approach

• Safety reminder: Airbag and pretensioner systems contain energetic devices. Do not perform invasive testing on undeployed devices. If you must work near airbags, disconnect the vehicle battery, wait the recommended de-energization period (typically 10+ minutes, vehicle-specific) and follow OEM procedures for SRS service. Use proper ESD precautions and consult OEM service information before any repair that touches airbag modules, pretensioners, or the clock spring.
• Tools to have handy: OBD-II scan tool capable of reading SRS/multi-system codes, OEM or high-quality generic SRS diagnostic tool, multimeter, wiring diagrams for steering wheel/seat harnesses, service manuals/TSBs for the vehicle, and a clock spring test kit if available.

Diagnostic steps

1) Confirm and characterize the code

• Read the DTC with an appropriate scan tool and check freeze frame data and any pending codes.
• Note the vehicle speed, ignition state, and other data from freeze frame. Some manufacturers encode fault context (e.g., steering wheel rotation, seat occupancy state) that can guide testing.
• Check for related DTCs in the SRS category (e.g., other B codes, or C codes) that may indicate a broader airbag system fault.

2) Confirm scope and gather context

• Determine whether the fault is intermittent or persistent.
• Identify whether the issue is localized to a specific seat (e.g., driver seat) or a global SRS fault.
• Review vehicle-specific service bulletins or recalls related to airbags, pretensioners, or occupant sensing devices.

3) Visual and mechanical inspection (non-destructive)

• Inspect the steering wheel clock spring area for damage, wear, or excessive movement. A damaged clock spring is a frequent contributor to intermittent or persistent airbag/pretensioner faults.
• Inspect wiring harnesses and connectors in the following areas for damage, corrosion, crushed insulation, or loose connections:
  • Under the driver's seat (seat wiring harness, occupancy sensor connectors if present).
  • Steering wheel and column area (airbag connector, clock spring connectors, hazard/airbag wiring).
  • Anywhere the harness routes through seats or pillars where abrasion could occur.
• Look for signs of previous airbag service, tampering, or after-market modifications that could affect connections.
• Check fuses related to SRS in the fuse box; verify fuse integrity.

4) Electrical checks and continuity testing (where safe and appropriate)

• With the battery and airbag system de-energized per OEM guidelines, inspect harness continuity for the airbag/pretensioner circuits between the airbag module connectors and the steering wheel/seat connectors. Use manufacturers' wiring diagrams to identify the correct circuits (often associated with the airbag/pretensioner lines and clock spring communications).
• Check for proper grounding and absence of open circuits or shorts to ground, battery positive, or other circuits. Look for any signs of short to ground or short to supply in suspected wires.
• If you have access to a vehicle-specific SRS diagnostic tool, perform a module self-check or actuator test as permitted by the tool and OEM guidelines.

5) Focused component checks (manufacturer-specific)

• Clock spring: If the clock spring wiring or internal contacts are suspected, follow OEM procedures to test or substitute with a known-good assembly. A bad clock spring commonly causes SRS intermittent codes.
• Airbag module (SRS control unit): If there are indications of internal fault or intermittent communication issues with the airbag module, verify with OEM diagnostics or replace per OEM guidelines if fault criteria are met.
• Occupant classification/seat sensor (if vehicle uses such a sensor): Check sensor wiring and connections; inspect for seat padding issues, wiring harness damage, or sensor faults as directed by OEM procedures.

6) Clearing codes and validating the repair

• After correcting any wiring, connector, or component issue per OEM guidance, clear the DTCs with the scan tool and run the self-checks or drive the vehicle (as recommended by OEM) to verify the fault does not return.
• Do not rely solely on the absence of a fault code; verify that the SRS light remains off and that there are no new codes appearing during a short road test.
• If the fault persists after the above steps, escalate to OEM service or a qualified airbag technician. Recheck for service bulletins or recalls that may apply to your vehicle.

7) Post-repair checks and safety considerations

• Re-scan for DTCs to confirm no pending or current codes exist.
• Confirm the SRS warning light behavior on startup; the light should illuminate briefly and then go off if the system self-tests correctly.
• Ensure all durably secured harnesses are re-routed and protected against future abrasion.
• Document the repair steps taken, parts replaced, and any test results.

Probable Causes

Note: The following is a best-practice probability framework when diagnosing B0155 in the absence of vehicle-specific NHTSA data . Use OEM service data and charts for exact prioritization.

• Wiring harnesses and connectors in the airbag/pretensioner circuit (including seat, clock spring, and driver seat area): 40-60%
  Why: Common failure path due to flexing, abrasion, corrosion, and previous tampering or service.
• Clock spring failure or intermittent connection in the steering wheel area: 20-30%
  Why: Frequent contributor to airbag/clock-spring related DTCs, especially with steering wheel abuse or seat/column movement.
• Airbag control module (SRS control unit) fault or communication issue: 15-25%
  Why: Module faults do occur, though often after repeated fault cycles or prior repairs.
• Occupant classification/seat sensor or pretensioner circuit issue: 5-15%
  Why: Vehicle-specific configurations may place emphasis on occupant sensing; faults here can trigger B0155-like codes.
• Other intermittent or unknown causes (including recalls or service bulletin-driven conditions): 0-5%
  Why: Less common, but OEM-specific issues or recent recalls can apply.

Documentation and references

• General DTC framework and code categories (OBD-II): Wikipedia - OBD-II: Diagnostic Trouble Codes; OBD-II: Powertrain Codes
  Use for understanding that DTCs are part of the OBD-II diagnostic system and that the body (B) category exists as a code domain.
• Code categorization and standard definitions
  GitHub definitions provide standard code information mappings for OBD-II codes, including B codes. Use these as a baseline for code structure while prioritizing manufacturer-specific definitions.
• Emissions and test considerations (context only)
  While B0155 is not an emissions code, OBD-II diagnostics and the broader diagnostic environment include emissions testing considerations. This context helps frame the importance of a clean SRS diagnostic in regulatory environments.

What you should do next

• If you cannot locate a manufacturer-specific B0155 definition for your exact vehicle, don't assume a non-SRS fault. Start with SRS-focused checks (wiring, clock spring, airbag module, seat sensors) and verify there are no mixed codes from other sub-systems that could confuse interpretation.
• Always cross-check with OEM service information, recall/TSB databases, and any vehicle-specific diagnostic trees. This is critical because the exact fault definition for B0155 is typically manufacturer-specific.
• If any repair involves airbag components or pretensioners, ensure you follow OEM safety procedures and, when in doubt, involve a qualified airbag technician.

In summary

• B0155 is a body-related OBD-II code; the precise meaning is manufacturer-dependent. Use a careful, safety-focused diagnostic approach focused on airbag/pretensioner circuits, clock spring integrity, seat wiring, and the SRS module. Rely on OEM service data for the definitive fault description and repair procedures. offer a general framework for DTC concepts and body-code categorization but do not provide a vehicle-specific B0155 definition.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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