Comprehensive diagnostic guide for OBD-II code B0112

Notes

• B codes are the "Body" group of OBD-II trouble codes. The exact description of any B-code (including B0112) is vehicle-specific and defined in the OEM or service documentation. In other words, the general category is body-related, but the precise fault description for B0112 varies by make/model and may map to different body subsystems (e.g., interior electrical, door switches, seating sensors, lighting circuits, etc.). This aligns with the OBD-II framework where codes are organized into P (Powertrain), B (Body), C (Chassis), and U (Network) categories.
  • Source context: OBD-II DTC categorization and the existence of P, B, C, U codes are described in the OBD-II discussions. These sources confirm that DTCs are system-divided, with B codes covering body-related issues.

What you should know before you start

• The exact B0112 description will come from your specific vehicle's service information. The generic approach below focuses on how to diagnose and resolve body-related DTCs when B0112 appears.
• If the fault involves safety-critical systems (e.g., airbag/SRS circuits) or major vehicle control modules, follow the manufacturer's safety procedures and disconnect/lockout procedures per the service manual.

Symptoms

• Intermittent or persistent interior electrical issues: interior lighting flicker or not functioning, courtesy lights behaving oddly, or failure of a body-related switch/module to respond.
• Door/lock signaling anomalies: door ajar indicators misbehaving, power door lock/unlock intermittently failing, or incorrect status shown in the instrument cluster.
• Seat, occupancy, or console functions: seat track/occupancy sensor reports or related controls not operating as expected.
• HVAC or interior environment controls with abnormal feedback (in some vehicles, body codes relate to sensors/switches feeding the climate/comfort modules).

Because B0112 is vehicle-specific, confirm the exact fault description in the OEM service information or a trusted code database for the vehicle you're diagnosing.

Diagnostic Approach

1) Verify and document

• Retrieval: Confirm B0112 is current (not just a prior/previous code) and note any freeze-frame data, pending codes, and all codes shown with the scan tool.
• Context: Record when the fault occurs (vehicle speed, ignition state, door status, temperature, and whether it's intermittent or continuous). This helps correlate with the body system likely involved.

2) Review system scope and map the circuit

• Identify the body subsystem likely implicated by the OEM description for B0112 (e.g., lighting circuit, door switch circuit, seating sensor circuit, interior electronics). If the OEM provides a circuit diagram or a wiring harness map for the affected area, pull that up for inspection.
• Check for any related DTCs (in particular other B-codes or U/C codes) that can point to a common junction point or shared harness.

3) Visual and mechanical inspection

• Inspect the affected area(s) for obvious issues: damaged wiring, pin/socket corrosion, chafed insulation, moisture intrusion, loose grounds, or loose connectors.
• Check ground paths and battery negative connections that serve body modules; a poor ground can produce multiple spurious body codes.
• If a switch or sensor is involved in the suspected circuit, inspect its mounting, mechanical operation, and safety interlocks.

4) Electrical tests (fault finding on the circuit)

• Power and ground verification: With the ignition on as appropriate, verify that the expected voltage exists at the relevant pins of the affected module or connector. Confirm solid ground presence.
• Continuity and resistance testing: Check for open circuits, high resistance, or short to power/ground along the harness between the module and the switch/sensor.
• Connector integrity: Check for bent pins, misalignment, corrosion, or foreign material in the connector, and reseat with proper locking engagement.
• Component testing: If the fault is traced to a specific switch, sensor, or actuator, test the component per the service information (e.g., switch continuity, sensor resistance range, actuator function) and compare to OEM spec.

5) Module and software considerations

• If wiring and connectors check out, consider a possible fault within the body control module (BCM) or the related body subsystem module. This may require module reprogramming, software updates, or module replacement per OEM service procedures.
• Some B-codes can be related to sequential reads, sensor data, or fault memory within the BCM; clearing codes and then rechecking after a test cycle helps differentiate a stuck code from a true fault.

6) Functional verification

• After you address the suspected fault (repair wiring, replace a switch, reseat connectors, or update software), clear the DTCs and perform a controlled test to reproduce the condition.
• Road testing and scenario testing (e.g., door operation, interior lighting triggers, seating adjustments) will help verify that the fault is resolved and does not reoccur.
• Re-scan after a test drive to ensure the code does not return.

7) Safety considerations

• If the suspected fault involves SRS/airbag components or any safety-critical body system, follow OEM procedures precisely. Do not disturb airbag-related wiring or connectors without proper safety precautions. If necessary, disconnect the battery and wait the recommended time before servicing SRS-related circuits according to the service manual.

Probable Causes

• Wiring harness damage or poor/loose connectors in the affected body circuit: ~40%
  • Most body codes arise from harness wear, chafing, water intrusion, or corrosion at connectors.
• Faulty body module or related control unit (e.g., BCM, seat module, door module) or software issue: ~25%
  • A failing or improperly programmed module can generate B-codes when it misreads inputs or cannot communicate across the body network.
• Grounding or poor electrical ground path on the affected circuit: ~15%
  • Inconsistent grounds commonly produce intermittent DTCs and symptom clusters across body circuits.
• Short to power or short to ground within the circuit: ~10%
  • A pin-to-pin short or a short via a faulty switch can trigger or reproduce a B-code.
• Intermittent sensor/actuator fault within the circuit (stuck readings, intermittent operation): ~10%
  • Intermittent operation of a switch or sensor is a frequent source of sporadic B-codes.

Notes on probabilities

• These percentages are qualitative estimates intended to help prioritize diagnostic steps when OEM specifics are unavailable.

• If OEM data or GitHub standard code definitions indicate a particular sub-system for B0112 in your vehicle (e.g., door switch circuit fault, occupant sensor circuit fault, interior lighting circuit fault), prioritize that area first in your diagnostic flow.

What to document and record

• All test results (voltage readings, resistance measurements, pin conditions, connector cleanliness, ground integrity).

• The exact OEM description of B0112 for the vehicle (the generic "body" category is insufficient for repairs).

• Any software/firmware version numbers for related body modules.

• All repairs performed and post-repair test results, including re-scan results.

• General practice references on standard code definitions and field diagnostics are commonly found in GitHub repositories and official service information, which technicians use to map B0112 to vehicle-specific descriptions and test procedures.

Tips for next steps

• Obtain the OEM service information for the specific make/model/year to retrieve the exact B0112 description and the recommended test procedures.
• If you encounter intermittent symptoms, reproduce them in a controlled test to confirm intermittent connectivity or a failing module.
• When in doubt, isolate the affected circuit area (e.g., disconnect the suspected switch or module) to determine if the fault follows the circuit or remains with the device, which helps distinguish harness/connector problems from module faults.
• If the fault involves safety-critical systems (SRS, airbags, or occupant sensing) or if you're uncertain about the risk, escalate to the OEM diagnostic procedures and safety-first guidelines.

In summary

• B0112 is a Body-category OBD-II code; the exact fault description is vehicle-specific and must be taken from OEM/service documentation or a reliable code database.
• The diagnostic approach focuses on mapping the circuit, verifying power/ground, inspecting harnesses/connectors, testing components, and validating with a controlled test drive.
• Probable causes typically center on wiring/connectors, the body module, grounding, shorts, or intermittent sensor/actuator faults, with the precise likelihoods varying by vehicle.
• Safety is paramount when working on body and especially SRS-related circuits; follow OEM safety procedures and service manuals.

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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