Code
B1516
ALFA ROMEO
B — Body
Driver seat occupied switch circuit open
Views:
UK: 18
EN: 24
RU: 29
AI status
Completed
Completed
100%
Causes
- Open or broken wiring in the occupant detection/switch circuit
- Corroded, loose or contaminated connector at the seat switch or module
- Failed/defective seat occupied (occupant detection) switch or sensor assembly
- Faulty body control module, SRS/airbag module or poor ground at module
- Water/moisture or intrusion in seat harness, connector or switch
Symptoms
- Occupant detection indicator may show no occupant or incorrect occupant status
- SRS/airbag warning lamp or diagnostic light illuminated
- Seatbelt warning or chime may behave incorrectly for driver seat
- Possible disablement or changed deployment logic for passenger/driver restraints
- Stored B1516 code in SRS/BCM memory
What to check
- Retrieve full DTC list and freeze frame data with a capable diagnostic scanner (SRS/BCM)
- Visually inspect seat area, connector(s) under the seat and harness for damage, corrosion or moisture
- Check for aftermarket seat heaters, alarms or wiring that may have been spliced into the harness
- Backprobe the seat occupied switch connector with key ON and compare to expected signal/reference/ground
- Perform continuity check between switch connector and module connector with seat in multiple positions
- Wiggle test wiring and connector while monitoring live data or continuity to try to reproduce the fault
Signal parameters
- Exact voltages/resistances are manufacturer-specific — consult the Alfa Romeo repair manual.
- Typical behavior: closed switch/occupied condition often shows a low resistance to ground or a low voltage on the signal circuit; open circuit/empty condition often shows very high resistance (OL) or signal pulled to supply (reference) voltage via pull-up.
- Expected resistance: closed ≈ near 0–50 ohms across switch contacts (if mechanical), open ≈ OL/infinite. (Verify with service data.)
- Expected signal voltage with key ON: many systems use a 5 V or 12 V reference; open-circuit may read reference voltage, closed may read near 0–1 V. Confirm exact values in vehicle documentation.
Diagnostic algorithm
- Read and record all SRS/BCM codes and freeze frame using a diagnostic scanner; note related codes.
- Visually inspect connectors and harness under the driver seat for damage, contamination, or foreign objects. Repair any visible damage.
- Follow manufacturer SRS safety procedures before doing hands-on work (disable battery/power and wait required time per service manual).
- Backprobe the seat occupied switch connector with key ON (and SRS enabled as required by procedure) and measure signal voltage and reference/ground per service data. Compare to expected values.
- If open circuit suspected, perform continuity test between switch connector and control module connector pins. Move seat through full travel while monitoring continuity.
- If wiring is intact, disconnect the switch and measure switch resistance across its terminals with seat occupied/unoccupied. Replace switch if it does not change as specified.
- If wiring or connector is faulty, repair wiring or replace connector pins as needed, then re-test.
- After repairs, clear codes and perform an SRS system scan and live-data verification. Confirm code does not return and that occupant detection behaves correctly.
- If codes persist after wiring and switch checks, consider module diagnostics/replacement per manufacturer procedure and consult technical service bulletins.
Likely causes
- Damaged seat harness from seat adjustment mechanism
- Connector pins pushed out or bent at the seat module or under-seat harness
- Seat switch internal failure from wear or contamination
- Chafed wiring that opens when seat is adjusted
- Corrosion from spilled liquids in seat area
Fault status
Status
Driver seat occupied switch circuit open — open circuit detected in the driver seat occupant detection/switch wiring or switch. Inspect connectors, wiring and switch.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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