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Home / DTC / B1550 — SRS alarm Lamp circuit fail

B1550 — SRS alarm Lamp circuit fail

Detailed page for trouble code B1550.

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Code

B1550

MITSUBISHI B — Body

SRS alarm Lamp circuit fail

Brand: MITSUBISHI
Type: B — Body
Views: UK: 18 EN: 37 RU: 31
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Page language: EN

Causes

  • Faulty instrument cluster lamp or LED element
  • Open or short in the SRS lamp wiring harness or connector
  • Corroded or loose connector at the instrument cluster or SRS control module
  • Blown fuse supplying the cluster/SRS lamp circuit
  • Faulty SRS control module (ECU) output driving the lamp
  • Aftermarket electrical accessories or recent repairs that disturbed wiring

Symptoms

  • SRS warning/airbag lamp stays ON or does not perform normal key‑on self‑check (may remain off or flash)
  • Possible additional SRS related warning lights or stored airbag codes
  • Vehicle may log related communication or circuit DTCs
  • Driver sees SRS lamp behaviour change after wiggle of dash harness

What to check

  • Read and record all stored SRS and related codes with a capable scanner (note freeze frame and code history)
  • Visually inspect instrument cluster area, harness, and connectors for damage, corrosion, or loose pins
  • Check fuse(s) for instrument cluster / SRS lamp circuit
  • Verify lamp behavior on key‑on: lamp should illuminate for self‑check then go out (see signal params)
  • Check for recent repairs or aftermarket installs that could have disturbed wiring (alarms, stereos, battery terminals)

Signal parameters

  • Key ON (engine OFF): SRS lamp should illuminate during self‑test (~3–10 seconds) then go out if system OK
  • Probe lamp feed at socket with ignition ON: feed should be close to battery voltage (~12V); the SRS ECU typically pulls the lamp circuit to ground to illuminate during self‑test
  • Continuity: there should be continuity through the lamp element and harness to the instrument cluster; open circuit indicates broken wiring or failed lamp
  • Incandescent lamp typical DC resistance low (tens of ohms); LED modules have higher impedance—compare with known-good spec or identical unit when possible

Diagnostic algorithm

  1. Safety first: follow manufacturer SRS safety procedure before doing work. Disconnect battery negative and wait the manufacturer‑specified time before probing SRS components.
  2. Scan and document DTCs and clear codes. Reproduce and see if B1550 returns.
  3. Perform a visual inspection of instrument cluster, dash harness, steering column, SRS ECU connector and related grounds for damage, corrosion, or loose pins.
  4. Check related fuses (instrument cluster / SRS) and restore if blown; recheck lamp behavior.
  5. With ignition ON (and SRS safety measures observed), verify SRS lamp self‑check: lamp lights then goes out. If lamp does not light, remove cluster panel to access lamp/socket or LED connector.
  6. Measure voltage at the lamp feed and return/ground while performing key‑on test. Confirm feed voltage (~battery voltage) and that the SRS ECU pulls the circuit to ground to illuminate the lamp. Use a test lamp or scope if available rather than relying only on LED indicators.
  7. Check continuity between instrument cluster lamp connector and SRS ECU connector; check for shorts to chassis ground or battery positive.
  8. Wiggle test wiring with connector plugged in while monitoring the circuit for intermittent faults.
  9. If wiring and connectors OK, swap/bench test or replace the instrument cluster lamp/LED module or instrument cluster per manufacturer guidance.
  10. If cluster replacement does not cure fault, investigate/replace SRS control module or repair harness between SRS ECU and cluster. After repairs, clear codes and perform full SRS system check with scan tool.
  11. Always reassemble and verify the SRS lamp performs normal self‑test and no SRS deployment components were disturbed. Recheck for stored codes and test‑drive as required.

Likely causes

  • Defective instrument cluster lamp/LED or socket
  • Open/poor connection at the instrument cluster connector
  • Wiring short to power or ground in the lamp harness near the dash
  • Corrosion or bent pins at the SRS ECU or cluster connector
  • Less likely: internal SRS ECU driver failure

Fault status

⚠️ Status
SRS warning lamp circuit malfunction detected — lamp may be open, shorted, or driver/connector fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1500 B1551 B1570 B1600 B0101
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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