B1187

Code

Generic B — Body

Passenger Seat Occupant Detection Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 19 EN: 28 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or disconnected wiring harness under passenger seat
Corroded or loose connector at the sensor or SDM/airbag module
Faulty occupant detection sensor pad or seat module
Water/moisture intrusion into sensor, connector, or seat
Poor ground or power supply to the sensor circuit
Faulty Supplemental Restraints Module (SDM) or Body Control Module (if applicable)

Symptoms

Passenger airbag ON/OFF indicator behaves incorrectly or is illuminated
Passenger airbag disabled message displayed or airbag status lamp illuminated
Airbag readiness light or fault indicator on dash
Passenger seat belt/airbag warnings may behave unexpectedly
Possible inability to enable passenger airbag even with occupant present

What to check

Use a scan tool to read B1187 plus any related fault codes and freeze-frame data
Visually inspect passenger seat area: connectors under seat, harness routing, signs of chafing, corrosion, or water damage
Check for aftermarket seat covers or cushions and remove to retest
Verify connector engagement and inspect pin condition at sensor and SDM/BCM
Check for Technical Service Bulletins or recalls related to occupant detection
Confirm whether the airbag/passenger status indicator matches actual occupancy

Signal parameters

Reference supply present at sensor connector (typically a low-voltage reference; many systems use ~5V reference)
Signal voltage or data changes when occupant seats vs. seat empty (sensor output should vary with load)
Open-circuit (infinite resistance) or short to ground/power at sensor leads indicates wiring fault
Low resistance continuity expected between sensor ground and chassis ground
Diagnostic data (via scan tool) may show seat occupancy state, sensor resistance, or internal sensor fault flags

Diagnostic algorithm

Connect a capable scan tool, read and record B1187 and any additional DTCs and freeze-frame data; clear codes and attempt to reproduce.
Visually inspect the passenger seat, seat track area, and underside for damaged wiring, disconnected or corroded connectors, signs of moisture, or aftermarket seat covers. Repair obvious damage.
With battery safe and vehicle off, disconnect battery if required by manufacturer safety procedures before working near airbag connectors. Follow all SRS safety precautions.
Access the occupant detection sensor connector under the seat. Check pin condition and connector retention. Reconnect and ensure secure seating; wiggle harness while monitoring codes or live data.
Backprobe or use the scan tool to monitor sensor reference and signal lines (per manufacturer procedure). Verify reference voltage present and that signal changes with a known weight (use recommended test weight or a human subject per safety guidelines).
Measure resistance/continuity of sensor circuit and ground. An open, short to power, or short to ground indicates wiring or sensor failure. Repair wiring or replace connector as needed.
If wiring and connectors are good but the sensor does not respond correctly, replace the occupant detection sensor/seat module following manufacturer service instructions.
After repair or replacement, perform any required sensor recalibration or SDM/seat module relearn procedure using the scan tool. Clear codes and retest with occupants to confirm correct behavior.
If fault persists after sensor and wiring replacement and correct calibration, consider SDM or BCM fault—verify CAN/comms and consult manufacturer service documentation before replacing modules.

Likely causes

Connector or wiring chafed or pinched under seat from seat movement
Corrosion or bent pins at the seat harness connector
Physical damage to the sensor pad (seat cushion) from wear or liquid spill
Loose or missing ground at seat frame
Interference from aftermarket seat cover blocking sensor readings

Fault status

⚠️ Status

Passenger seat occupant detection sensor circuit malfunction. May disable or incorrectly enable the passenger airbag; inspect seat sensor, wiring, connectors, and perform required calibrations.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours