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Home / DTC / B1B74 — Side impact sensor(LH) 3

B1B74 — Side impact sensor(LH) 3

Detailed page for trouble code B1B74.

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Code

B1B74

MITSUBISHI B — Body

Side impact sensor(LH) 3

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

Causes

  • Open or short in the side impact sensor (LH) #3 wiring
  • Corroded, bent or disconnected sensor connector
  • Failed side impact sensor (internal fault)
  • Poor or lost ground/ reference voltage to the sensor
  • Faulty airbag (SRS) control module or internal module error
  • Damage to wiring harness from collision or repair work

Symptoms

  • SRS / airbag warning lamp illuminated on instrument cluster
  • Related side airbag(s) may be disabled until the fault is cleared
  • Possible stored freeze-frame data showing event or circuit fault
  • Vehicle may fail SRS diagnostic self-test
  • In rare cases, inconsistent sensor data reported to ECU (diagnostic tool)

What to check

  • Read and record all SRS codes and freeze-frame data with a manufacturer-level scan tool
  • Perform a visual inspection of the LH side impact sensor, connector and surrounding wiring for damage, corrosion or moisture
  • Wiggle-test the harness and connector while watching live data for changes or code set
  • Check fuse(s) related to the airbag/SRS system
  • Verify the sensor is mounted and not physically damaged or loose
  • Compare live sensor signal to expected values using a scan tool (if supported)

Signal parameters

  • Reference supply voltage to sensor: typically ~5 V (check factory spec)
  • Sensor idle/output voltage: often around mid-supply (approx. 2–3 V) at rest (verify with service manual)
  • Expected continuity: low resistance from sensor ground to chassis ground
  • No open circuit between sensor signal pin and ECU signal pin (continuity check)
  • Diagnostic tool may show sensor values or status bits rather than raw voltage on some vehicles

Diagnostic algorithm

  1. Use a diagnostic scanner to read all SRS codes and note related/preceding codes and freeze-frame data.
  2. Visually inspect the LH side impact sensor, mounting, connector and wiring for damage, corrosion, or water ingress. Repair obvious issues.
  3. With ignition ON (or per service manual), backprobe the sensor connector and verify reference voltage, signal voltage at rest, and ground continuity against factory specifications.
  4. Wiggle the harness and connector while monitoring live data or DTCs to detect intermittent faults.
  5. Perform continuity and resistance checks from the sensor connector pins to the airbag ECU connector to confirm no open or high-resistance connections.
  6. If wiring and connectors test good, disconnect the sensor and measure its terminal resistances/voltages per the service manual. Replace the sensor if out of spec or internal fault indicated.
  7. If a new sensor is installed, clear codes with scan tool and run SRS self-test/initialization procedure as required by manufacturer.
  8. If fault persists after replacing sensor and repairing wiring, consider diagnosing the airbag ECU (use specialist tools or consult dealer-level diagnostics).
  9. After repair, verify that the SRS warning lamp goes out and no related codes return; test drive as required and re-scan.

Likely causes

  • Connector at LH side impact sensor is loose, corroded or contaminated
  • Wiring harness chafed or broken between sensor and airbag ECU
  • Sensor electronics failed (common with water ingress or impact)
  • Loss of reference voltage (5V) or ground at the sensor connector
  • Intermittent connection due to pin deformation or poor crimp

Fault status

⚠️ Status
Airbag control unit detected malfunction in left-hand side impact sensor #3 circuit. SRS warning lamp likely illuminated and related side airbag may be disabled until fault is cleared and system verified.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

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406

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