Comprehensive diagnostic guide for OBD-II code B0142

Important Notes

• OBD-II trouble codes are organized into categories: P (Powertrain), B (Body), C (Chassis), and U (Network). This general structure is described in the OBD-II overview.
• The same Wikipedia OBD-II documents note that there are Powertrain Codes (P) as a major category, with other categories (including B) covering different vehicle subsystems. This helps frame how B-codes relate to body/electrical systems rather than powertrain.
• The exact OEM-specific meaning of a given B-code (like B0142) is not provided in the general articles you supplied. For OEM/repair-database definitions, you should consult the vehicle's service information or a dedicated code database. The general approach below follows the diagnostic framework described in these sources and is augmented with ASE-field-diagnostic best practices.

What This Code Means

• B codes are "Body" electrical/operative codes. The B0142 designation indicates a body-domain issue, but the precise OEM-defined fault description for B0142 is not included . Therefore, treat B0142 as a body-related DTC and verify its OEM definition for the exact circuit/component involved (e.g., door switches, lighting circuits, BCM inputs/outputs, etc.). Use OEM service information or a vehicle-specific database to pin down the exact fault target.
• Use the general B-code diagnostic framework below and then confirm the exact meaning via OEM documentation or a current repair database.

Symptom sources (typical for body codes)
Because the exact B0142 symptom description is not , consider common body-code symptoms that may accompany B-series codes:

• Interior/exterior lighting issues (flickering, lights not turning on/off as expected)
• Door/hood/trunk operation irregularities (locks, latch signals, door ajar warnings)
• Mirror controls or other body actuators not responding
• Central locking/unlock problems
• Any instrument cluster or BCM-related warning indicators

Diagnostic roadmap (step by step)

1) Confirm the fault and gather data

• Use a scan tool to confirm B0142 is currently stored (not just history). Note any Freeze Frame data, readiness monitors, and any related codes (P, C, U codes in proximity).
• Record vehicle make/model/year and any OEM/repair database code description for B0142 to map the precise circuit.

2) Verify normal/typical behavior and symptom correlation

• Cross-check the user-reported symptoms against body-system behavior that B-series codes commonly affect (doors, locks, lighting, mirrors, BCM inputs/outputs).
• If multiple body subsystems are involved, expect possible BCM or grounding issues, or harness/connectors affected by movement or moisture.

3) Visual and access inspection

• Inspect all relevant body circuits that commonly fall under B-codes in the given vehicle (doors, lighting, locks, mirrors, BCM connectors). Look for:
  • Damaged or corroded connectors, loose grounds, or signs of water ingress
  • Damaged wiring harnesses (pinches, chafing, exposed conductors)
  • Burn marks, melted insulation, or signs of short exposure
• Confirm that all related fuses are intact and that power feeds to the Body Control Module (BCM) and related circuits are present.

4) Electrical checks (base vehicle wiring and power)

• Check the BCM ground connections and any major body chassis grounds. A poor ground can create intermittent or permanent B-code faults.
• Verify supply voltages to relevant circuits (e.g., power to door lock relays, lighting circuits, or door ajar switch circuits) and test for voltage drop where appropriate.
• Use a wiring diagram to identify the exact circuits involved with B0142 in your vehicle (consult OEM service information).

5) Circuit-specific checks (targeted testing)

• If the OEM description suggests a door or switch circuit, test the input and output signals:
  • Door switches (open/close, latch input to BCM)
  • Lock actuators or window/mirror actuators if implicated
  • Lighting control circuits (interior/exterior lights) and their switches
• Check for proper signal integrity:
  • Continuity and resistance checks on suspected lines with the system powered as appropriate
  • Inspection of grounds on signal lines (checking for unintended ground paths)
• Check for BCM communications faults:
  • Ensure BCM is awake and able to communicate on the vehicle's data bus (CAN or other networks) if the OEM indicates a networked body issue
  • Look for conflicting signals or multiple modules reporting issues

6) Functional/system tests

• If possible, perform actuator tests via the scan tool (e.g., actuate door locks, mirror motors, lighting circuits) to observe responses and confirm if the issue follows a particular component or is interdependent.
• Test for intermittent behavior by cycling ignition and using the affected systems under various conditions (temperature, humidity) to reproduce or rule out intermittent faults.

7) Cross-check with other codes and symptoms

• Review any related codes in other categories (P, C, U) that might indicate a broader control/module or network problem that could manifest as a B0142 fault.
• If only B0142 appears, the fault is likely localized to a specific body circuit or the local BCM input/output.

8) Probable causes

Note: The exact cause of B0142 is OEM-specific; the following are generalized body-code failure patterns with probabilities (not ). If you have NHTSA complaints data for your vehicle's year/model, use those for probabilistic weighting; otherwise use field experience as a guide.

Common Causes

• Wiring harness and connectors (damage, corrosion, moisture, chafing, poor crimps): 40-55%
  • Why: Body circuits are exposed to door jamb flexing, moisture, and frequent movement; connectors can loosen or corrode over time.
• Faulty body switch/sensor (door ajar switch, door latch sensor, interior lighting switch, mirror control switch): 20-30%
  • Why: These components wear out or fail to provide clean signals to the BCM.
• Body Control Module (BCM) fault or miscommunication with other modules: 10-20%
  • Why: BCM failures or software glitches can produce a generic or misrouted B-code.
• Ground or power supply issues (bad ground strap, chassis ground, fuse/link faults): 5-15%
  • Why: Inconsistent ground can create spurious signals on body circuits.
• Intermittent/unknown or miscellaneous faults (shorts, opens, or uncharacterized faults): 0-5%
  • Why: Some faults manifest intermittently and are difficult to categorize without OEM data.

Note on the numbers: These percentages are provided to give a practical diagnostic emphasis based on general field experience for body-dominated codes. They are not sourced from NHTSA data . When possible, use NHTSA complaint data for vehicle-specific weighting; if not available, rely on ASE experience and the OEM's wiring diagrams to guide fault isolation.

Repair and Verification

• If a specific component is implicated by OEM documentation (e.g., a door ajar switch or a particular BCM input):
  • Replace or repair the faulty switch/sensor or the affected actuator as indicated.
  • Re-seat and clean connectors; replace damaged connectors or pigtails; ensure locking tabs and seals are intact.
  • Repair or replace corroded wiring harness sections; use proper automotive-grade splices if needed.
• If BCM or network-related fault is suspected:
  • Inspect CAN/vehicle network connections and power to the BCM; reset/reinitialize modules if OEM procedure allows.
  • Update or reflash BCM software if applicable per OEM guidelines after confirming with the software version.
• If wiring/grounding is suspected:
  • Re-secure or replace ground straps; clean corrosion from ground points and ensure proper torque on fasteners.
  • Trace the circuit to locate shorts or opens and repair accordingly.
• After any repair:
  • Clear the DTC memory, perform a vehicle-specific drive cycle, and re-scan to confirm the code does not return.
  • Verify the repaired function through a representative test (e.g., door operation, lighting, mirror control) and note any abnormal behavior for functional testing.
• If B0142 remains or recurs despite repairs:
  • Revisit OEM service information for the exact definition of B0142 and targeted troubleshooting steps.
  • Consider a BCM replacement only after ruling out harness, connection, and sensor faults, and after OEM-recommended diagnostic steps are exhausted.

Safety Considerations

• Always follow automotive safety practices. Disconnect the battery if you will be disturbing airbag-related circuits or if you work on high-energy body circuits near safety devices.
• Use insulated tools and avoid creating shorts during testing of wiring harnesses and connectors.
• When dealing with door/latch and locking mechanisms, ensure the vehicle is secure and cannot unexpectedly move or close on personnel.

Documentation and references

• General OBD-II framework and DTC structure:

  • Wikipedia: OBD-II → Diagnostic Trouble Codes (describes DTC categorization and the role of codes such as P, B, C, U)
  • Wikipedia: OBD-II → Powertrain Codes (context for powertrain (P) versus other categories; helps frame where B codes fit in the overall system)

• Additional guidance and conventions:

  • Standard code naming conventions and body codes note that B codes refer to body electrical systems. For precise B0142 OEM meaning, consult the vehicle's service information.

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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