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Home / DTC / B1407 — FR impact sensor low voltage

B1407 — FR impact sensor low voltage

Detailed page for trouble code B1407.

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B1407

MITSUBISHI B — Body

FR impact sensor low voltage

Brand: MITSUBISHI
Type: B — Body
AI status
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Page language: EN

Causes

  • Damaged or corroded FR impact sensor connector or terminals
  • Broken, shorted or pinched wiring between FR sensor and airbag control module
  • Open or low reference supply (fuse, wiring, or ECU power output) to the sensor
  • Failed/shorted FR impact sensor (internal electronics)
  • Poor ground at sensor or control module
  • Intermittent fault from water ingress or physical damage after a collision

Symptoms

  • SRS / airbag warning lamp illuminated on instrument cluster
  • Diagnostic trouble code B1407 stored in SRS module
  • Possible related SRS faults or other sensor codes present
  • In rare cases, diagnostic self-test may show intermittent related faults

What to check

  • Read and record SRS codes and freeze frame data with a capable scan tool
  • Visual inspection of FR impact sensor, connector, and harness for damage, corrosion, or water ingress
  • Check vehicle service history for recent collisions or repairs in the FR area
  • Inspect SRS-related fuses and battery voltage at the time of test
  • With ignition ON (and safety precautions), measure reference supply voltage at the sensor connector
  • Verify good ground continuity between sensor ground terminal and chassis/ECU ground

Signal parameters

  • Reference supply: typically a regulated sensor supply (commonly ~5 V) — confirm exact value in factory manual
  • Sensor output/signal: should be within manufacturer-specified range at rest (consult service data); a very low signal (< expected range) indicates low-voltage condition
  • Ground: low resistance/continuity to chassis ground or ECU ground terminal
  • Connector condition: no bent/missing pins and secure locking mechanism (visual and continuity check)
  • Note: always confirm exact numeric values and pin assignments from the Mitsubishi service manual for the specific model/year.

Diagnostic algorithm

  1. Safety first: Disable the vehicle battery and follow manufacturer SRS safety procedures before disconnecting or handling airbag components.
  2. Connect an OEM-capable SRS scan tool. Read and record B1407 and any other SRS codes; clear codes and see if B1407 returns.
  3. Perform a visual inspection of the FR impact sensor, mounting, connector and harness for damage, corrosion, water, or impact signs.
  4. With ignition ON (battery connected) and following safe practices, backprobe the sensor connector and measure: reference supply voltage, signal voltage, and ground continuity. Compare to factory specs. If reference supply is absent/low, trace back to fuse/ECU power.
  5. Check continuity and resistance of wiring between the sensor and SRS control module; look for shorts to ground or B+ and open circuits.
  6. Wiggle test: wiggle harness and connectors while monitoring live data/voltages to find intermittent connections.
  7. Repair any damaged wiring or connector defects (clean, repair, replace connector or harness section). Use correct crimps and insulation methods.
  8. If wiring and connectors are good and supplies are within spec but the sensor shows low output or fails self-test, replace the FR impact sensor with a correct OEM part.
  9. After repairs, reconnect battery, clear SRS codes with the scan tool, perform required SRS system initialization or diagnostics per factory procedure, and verify the SRS lamp is extinguished and no B1407 returns.
  10. If fault persists after sensor replacement and wiring verification, consider inspection or replacement of the airbag control module by a qualified technician.
  11. Always follow manufacturer procedures for handling, disposing, and replacing airbag components.

Likely causes

  • Corroded/pushed-back connector at the FR impact sensor
  • Wiring chafed and shorted to chassis ground or to battery positive near sensor harness routing
  • Failed impact sensor following minor impact or exposure to moisture
  • Blown or loose SRS-related fuse or poor ECU power connection
  • Intermittent connector contact due to bent pins

Fault status

⚠️ Status
FR impact sensor circuit — low voltage detected. SRS/airbag warning light on. Check sensor supply, wiring, connector and sensor. Follow SRS safety procedures before repair.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1400 B1401 B1402 B1403 B1408 B1409
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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