B2584

Code

Other B — Body

Child Seat Detection Circuit Open

Brand: Other

Type: B — Body

Views: UK: 25 EN: 30 RU: 24

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or disconnected wiring/harness under passenger seat
Damaged or broken connector terminals at seat or Occupant Classification ECU (OCU)
Failed or damaged seat occupancy/child seat sensor mat/module
Corrosion, water ingress or physical damage to sensor or connectors
Blown related fuse or loss of power/ground to sensor circuit
Faulty Occupant Classification ECU or wiring short upstream of ECU

Symptoms

Passenger airbag light or SRS warning lamp illuminated
Passenger airbag disabled message or indicator
Occupant classification/airbag warning on scan tool and DTC stored
Passenger seat may not detect occupant or child seat correctly
Possible intermittent SRS or seatbelt warning depending on wiring condition

What to check

Read and record freeze frame and all stored SRS/occupant classification codes with a capable scan tool
Visual inspection of passenger seat (around seams), underside of seat and floor: look for water, corrosion, damaged wiring and loose connectors
Confirm presence of relevant fuses and inspect for blown fuses
Backprobe/pin-probe sensor connector with ignition ON and check for reference/power and ground signals at the connector
Measure continuity between the sensor mat connector and the Occupant Classification ECU harness connector
Wiggle harness and connectors while monitoring live data or resistance to try to reproduce fault

Signal parameters

Circuit behavior: open circuit = very high resistance/infinite; expected closed circuit = measurable continuity between mat and ECU
Supply/reference: sensor circuits typically have switched power (12V or ignition) and a low-voltage reference (often 5V) — verify presence of both with key ON
Sensor output: occupant detection modules often send a variable voltage or data to the OCU; an open will show no/erratic voltage or out-of-range values
CAN or data bus: occupant classification status may be transmitted over CAN — check for valid messages on bus if system uses networked modules
Typical fault detection: ECU detects resistance or voltage outside expected range and sets DTC B2584

Diagnostic algorithm

Use an OBD-II/SRS-capable scanner to read codes and live data; note symptom status and any related codes.
Visually inspect passenger seat upholstery, seams and underside; look for foreign objects, water or visible damage to the sensor mat.
With battery connected and ignition ON (follow manufacturer safety for SRS circuits), locate the seat occupancy/child sensor connector under the seat and inspect for corrosion, bent pins or loose terminals.
Check fuses and ground points related to the occupant classification system.
Backprobe the sensor connector: verify reference voltage/power and ground are present. If power/ground missing, trace to fuse/relay/ground.
Measure continuity/resistance between sensor mat connector and the Occupant Classification ECU connector. An open (~infinite resistance) indicates harness/mat break. If continuity OK, check resistance value compared to manufacturer spec (if available).
Wiggle test harness and connectors while observing live data for intermittent opens.
If a suspect section of wiring is found, repair or splice per manufacturer procedure and re-test. If wiring appears OK, bench-test or replace the sensor mat/module.
If wiring and mat test good, suspect Occupant Classification ECU — verify CAN/data and replace ECU only after confirming upstream circuit integrity.
After repairs, clear codes and perform occupant detection/airbag system self-test; verify code does not return and system functions normally.

Likely causes

Disconnected or damaged connector under the passenger seat (most common)
Broken sensor mat or wiring harness (pinched/cut wiring)
Water intrusion or corrosion on mat or connector
Faulty seat occupant classification module/ECU
Blown fuse or poor ground

Fault status

⚠️ Status

Child seat detection circuit open — occupant detection sensor circuit shows an open condition. May disable passenger airbag or set occupant classification fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours