B2623

Code

Generic B — Body

Occupant Classification System — Front Passenger Seat Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 10 EN: 19 RU: 8

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Page language: EN

Causes

Disconnected or corroded connector under the front passenger seat
Damaged/frayed wiring harness (open, short to ground, or short to battery)
Faulty occupant classification sensor mat (pressure/weight sensor array)
Faulty Occupant Classification Module (OCM) or SRS control module
Water or debris intrusion into the seat or sensor mat
Aftermarket seat covers, cushions, or repairs that alter sensor function

Symptoms

SRS/airbag warning lamp illuminated
Passenger airbag disable/enable indicator behaves incorrectly or shows 'unknown'
Passenger occupancy or seatbelt reminders incorrect or not present
DTC B2623 stored and may reappear after code clear
Possible inability to complete occupant classification calibration

What to check

Read and record stored DTCs and freeze-frame data with a capable scan tool.
Verify SRS/airbag lamp status and any related DTCs in the SRS module.
Perform a visual inspection of the passenger seat: connectors, wiring, sensor mat area for contamination or damage.
Check for aftermarket seat covers or objects between the occupant and seat that could affect sensors.
Verify power, ground and fuse(s) for the occupant classification/seat system.
Check for communication faults on the vehicle data bus (CAN) to the OCM/SRS module.

Signal parameters

Sensor circuits typically use a low-voltage reference (often 5V) and return a variable signal or resistance that changes with load; some systems use frequency or PWM outputs.
Fault indications include: open circuit (infinite resistance), short to ground (near 0 Ω), short to battery (constant high voltage), or intermittent/noisy signal on the data line.
Module reports on CAN: occupancy status values such as 'No occupant', 'Child', 'Adult', or 'Invalid/Unknown'.
Expected behavior: signal changes smoothly with applied load; sudden drops/spikes or unchanged values indicate wiring/sensor faults.

Diagnostic algorithm

Safety first: follow manufacturer SRS safety procedures before working on the seat or SRS components (disconnect battery and observe required wait times per manufacturer).
Connect a professional scan tool. Confirm B2623 and note any related SRS codes and freeze-frame data. Clear the code and see if it returns immediately or after a test.
Visually inspect the passenger seat area: remove lower trim panels and access connectors under the seat. Look for corrosion, bent pins, disconnected plugs, water, or foreign objects.
With ignition on (and battery safety observed), monitor live data for the occupant classification module while gently moving the seat and harness (wiggle test) to try to reproduce the fault. Watch for signal dropouts or error codes returning.
Verify power and ground at the occupant sensor/module connector(s). Check related fuses and module supply voltages.
Perform continuity/resistance checks on the harness between the seat sensor connectors and the occupant classification module. Look for opens or shorts to ground/battery. Repair any damaged wiring.
If harness and connectors check good, test the sensor mat per manufacturer procedure (resistance/voltage/frequency checks). If the mat is removable, a bench test may be possible following service manual steps.
If a sensor mat or module replacement is required, follow manufacturer instructions for part replacement and required occupant classification calibration/learn procedure after installation.
After repairs and calibrations, clear DTCs, confirm that the code does not return, and verify proper passenger airbag indicator operation and SRS lamp extinguishes. Perform road or static verification as required by manufacturer.

Likely causes

Loose/disconnected connector or pin damage under the seat
Open or intermittent wiring in the seat harness from repeated seat movement
Failed sensor mat (most common with age or water exposure)
Contamination (liquid or foreign objects) inside the seat cushion affecting the mat