B0522

Code

Generic B — Body

Passenger Occupant Classification Sensor Circuit Fault

Brand: Generic

Type: B — Body

Views: UK: 5 EN: 9 RU: 7

AI status

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Page language: EN

Causes

Damaged or chafed wiring in the seat/under-seat harness
Loose, corroded or bent connector pins at the sensor or SRS control module
Water/moisture or contamination in the seat cushion or connector
Faulty occupant classification sensor (seat mat, load cell, or capacitance sensor)
Defective occupant classification module or restraint control module software/hardware
Poor ground or intermittent connection

Symptoms

SRS/airbag warning lamp illuminated
Passenger airbag may show as disabled or enabled incorrectly on dash (occupant detection incorrect)
Passenger airbag status indicator unpredictable or does not change with occupant presence
Possible inability to perform occupant classification calibration
No other visible driveability symptoms (fault limited to restraint system)

What to check

Read and record DTCs and freeze frame data with a compatible scan tool
Check for related SRS codes and history (other occupant sensor or module faults)
Visual inspection of passenger seat: connectors, wiring routing, signs of damage, moisture, or foreign objects
Visually inspect and reseat harness connectors under the seat and at the restraint control module
Monitor live data/parameter for the occupant classification sensor with scan tool while sitting in passenger seat and while wigging connectors
Perform a wiggle/see-if-code-changes test on the seat harness to reproduce the fault

Signal parameters

Typical sensor circuits use a reference supply (often 5 V) and a signal return — expect a stable reference voltage at the sensor connector with respect to ground
Signal voltage commonly ranges between ~0–5 V; quiescent/nominal seat values often sit near mid-range and change with occupant weight or presence (exact values vary by manufacturer)
Open circuit may read very high impedance or no signal; short to ground shows near 0 V; short to battery shows near reference or battery voltage
CAN/serial message diagnostics: some systems report occupant classification status over the airbag network — message periodicity typically regular when healthy (consult manufacturer for exact frequency)

Diagnostic algorithm

Safety first: disable SRS power and follow vehicle manufacturer procedures before probing airbag system connectors or removing seat components.
Connect a capable scan tool and record B0522 plus any related codes and freeze frame data.
Inspect the passenger seat area: remove trim to access connectors, look for damaged wiring, water ingress, or foreign objects affecting the seat mat.
Visually inspect and reseat connectors under the seat and at the SRS control module; check for corrosion, bent pins, or pushed-out terminals.
With ignition on (and following safety guidance), backprobe the sensor connector: verify reference voltage, ground, and signal voltage. Compare to expected behavior while an occupant sits on the seat and while removed.
Perform continuity testing between the sensor connector and the restraint control module for signal, supply, and ground circuits; repair any open/short circuits.
If wiring and connectors are good, measure resistance or raw outputs of the occupant sensor elements (per manufacturer values). Replace the seat mat/sensor if values are out of specified range or intermittent.
If sensor and wiring check OK, consider occupant classification module or restraint control module fault — verify software level and perform recommended calibrations or module replacement per factory procedure.
After repairs, clear codes, perform required occupant classification calibration/learning procedure, then verify system returns to normal with no recurrent DTC and correct passenger airbag status.
If fault persists, consult manufacturer technical information for module-specific test procedures and wiring diagrams.

Likely causes

Open circuit or short to ground in the passenger seat sensor harness
Connector corrosion or pin pushed out at the sensor or ECU
Seat cushion mat damage or intrusion by seat heater/seat cover
Intermittent signal due to broken wire under the seat moving with seat travel
Sensor module failure after impact or water exposure

Fault status

⚠️ Status

Passenger Occupant Classification Sensor Circuit Fault — a sensor or circuit related to passenger detection is reporting an invalid or out-of-range signal. This can cause passenger airbag disable/enable errors and will illuminate the airbag warning lamp.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours