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Home / DTC / B1487 — Seatbelt alarm lamp harness open

B1487 — Seatbelt alarm lamp harness open

Detailed page for trouble code B1487.

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Code

B1487

MITSUBISHI B — Body

Seatbelt alarm lamp harness open

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Broken or chafed wiring in the seatbelt warning lamp circuit
  • Disconnected or corroded connector at the instrument cluster or harness splice
  • Faulty instrument cluster indicator lamp (bulb or LED)
  • Blown fuse or poor power supply to the lamp circuit
  • Open or poor ground to the lamp or instrument cluster
  • Faulty body control module / combination meter (less common)

Symptoms

  • Seatbelt warning/alarm lamp does not illuminate with ignition ON or when seatbelt unbuckled
  • Intermittent operation of the seatbelt lamp (works when wires are moved)
  • Related seatbelt reminder chime may not activate or may be inconsistent
  • A stored B1487 DTC in BCM/combination meter memory

What to check

  • Verify the DTC is current (not historic) and note freeze frame/ignition status
  • Visually inspect wiring and connectors for the seatbelt indicator between the instrument cluster and body harness for damage, corrosion, or disconnected plugs
  • Check related fuses and power supply circuits for the instrument cluster
  • Inspect the indicator lamp (bulb or LED) for signs of damage or failure
  • Perform a wiggle test on the harness and connectors while observing lamp behavior
  • Scan for other related DTCs (seatbelt buckle switch, BCM, instrument cluster codes)

Signal parameters

  • Battery voltage at lamp power terminal with ignition ON: approx. 11–14 V (when the lamp is powered)
  • Voltage at lamp connector when lamp is commanded ON: near battery voltage (if lamp is supplied with +12 V) or near 0 V if the module drives ground—consult vehicle wiring diagram
  • Continuity of lamp wiring: low resistance (typically
  • Resistance of a typical incandescent indicator bulb: a few ohms cold; LED evidence: near open if removed — rely on continuity checks
  • Open-circuit condition: infinite resistance or no voltage present at expected terminal

Diagnostic algorithm

  1. Retrieve and record DTC(s) and any freeze frame data. Clear codes and attempt to re-create the fault to confirm persistence.
  2. Visually inspect instrument cluster area, harness routing, and connectors for damage, corrosion, water intrusion, or pinched wires.
  3. Check fuses and power supply to the instrument cluster/BCM. Repair any blown fuses and retest.
  4. With ignition ON, measure voltage at the seatbelt indicator connector at the cluster and at the lamp end of the harness. Compare to battery voltage to detect an open feed.
  5. Check continuity between the instrument cluster connector pin and the indicator lamp connector pin with battery disconnected. An open (OL) indicates a break in the harness—repair wiring or connector.
  6. Inspect and test the indicator lamp itself. Replace the bulb or module if faulty, then verify circuit continuity.
  7. Check ground connection(s) for the cluster and harness. Clean and secure ground points as needed.
  8. If wiring and lamp are good, backprobe the module/combination meter output driver and verify operation while commanding the lamp (or during lamp test mode). If the driver does not respond but wiring is good, consider module fault.
  9. After repairs, clear codes and verify proper lamp operation under the conditions that previously set the code. Road test or cycle ignition to confirm no return of DTC.

Likely causes

  • Connector at instrument cluster or harness splice disconnected or corroded
  • Open wiring between combination meter and seatbelt indicator lamp
  • Failed indicator lamp (bulb/LED) causing open detection
  • Damaged harness from door hinge/floor area where harness flexes

Fault status

⚠️ Status
B1487 - Seatbelt alarm lamp harness open. Open circuit detected in the seatbelt warning lamp wiring between the indicator and control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

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406

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