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Home / DTC / B1B72 — Side impact sensor(LH)

B1B72 — Side impact sensor(LH)

Detailed page for trouble code B1B72.

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Code

B1B72

MITSUBISHI B — Body

Side impact sensor(LH)

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

Causes

  • Open or short in LH side impact sensor wiring harness
  • Corroded/loose connector at the LH side impact sensor
  • Internal failure of the LH side impact sensor
  • Water ingress or physical damage to the sensor or connector
  • Poor ground or battery supply to the SRS system
  • SRS (airbag) ECU fault or connector problem

Symptoms

  • SRS / airbag warning lamp illuminated on instrument cluster
  • Possible disabling of related side airbag(s) or seatbelt pretensioners
  • DTC B1B72 stored in SRS ECU; possible additional SRS codes
  • Vehicle safety system may report reduced protection (store/recorded in SRS)

What to check

  • Read SRS module code(s) and freeze-frame data with a factory-level scan tool that supports Mitsubishi airbag system
  • Check for other SRS or crash history codes (post-deployment lockouts)
  • Visual inspection of LH side impact sensor, mounting, wiring and connector for damage or corrosion
  • Check battery voltage and main SRS power/ground circuits before testing sensors
  • Back-probe connector to measure reference power, ground and sensor output (observe safety precautions)
  • Compare LH sensor readings to right-hand (RH) sensor values if available

Signal parameters

  • Reference/supply voltage: typically 5 V (verify with factory data) with ignition ON
  • Quiescent sensor output: often ~2.5 V (midpoint) — should be stable with no impact
  • Signal behavior: voltage should vary only on sharp acceleration/deceleration; not erratic
  • Expected continuity: low ohms between sensor ground and chassis ground; no short to battery
  • Connector pin resistance: near 0–1 ohm for power/ground circuits (wiring dependent)
  • CAN/LIN data: if sensor communicates digitally, expect valid messages to SRS ECU (use scan tool)

Diagnostic algorithm

  1. Safety first: Disable SRS power per manufacturer procedure (disconnect negative battery terminal and wait specified time) before disconnecting/handling connectors or removing the sensor.
  2. Use a factory-capable scan tool to confirm B1B72, read freeze frame and any related codes. Note conditions when fault occurred.
  3. Perform a thorough visual inspection of the LH side impact sensor, its bracket, connector and wiring for physical damage, corrosion or water intrusion.
  4. With ignition ON and using appropriate safety procedures, back-probe the sensor connector: verify reference voltage (5 V) and ground presence at the connector and measure the sensor signal voltage at rest (expected ~mid-rail ~2.5 V). Record values.
  5. Wiggle test wiring while watching live data/signals for intermittent changes. If signal collapses or DTC returns, suspect wiring/connector.
  6. Check continuity between the sensor connector and the SRS ECU connector for power, signal and ground pins (with battery disconnected). Repair any opens/shorts.
  7. If wiring and connectors check OK but signal is out of expected range or no output, replace the LH side impact sensor and retest.
  8. After any repair, clear codes with the scan tool, perform system checks and re-check for reappearance of the DTC. If codes persist, inspect/replace SRS ECU only after confirming all sensor circuits are good and following manufacturer procedures.
  9. If the vehicle shows crash history or deployment, suspect locked/disabled SRS components — follow manufacturer procedures for module replacement and system reset.

Likely causes

  • Broken/shorted signal wire between LH sensor and SRS ECU
  • Bent or corroded pins in sensor connector
  • Sensor internal electronics failed (no/erratic output voltage)
  • Connector contamination (moisture, rust) causing intermittent connection
  • SRS ECU not receiving/recognizing sensor signal due to ECU fault

Fault status

⚠️ Status
Side impact sensor (LH) circuit fault — open/short or out-of-range signal detected by SRS ECU.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1B71 B1B73 B1B70 B1B74
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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