B12C7

Code

Generic B — Body

Driver Seat Occupant Detection Sensor Circuit Fault

Brand: Generic

Type: B — Body

Views: UK: 5 EN: 9 RU: 5

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or disconnected sensor harness or connector
Corroded or contaminated connector pins
Failed occupant detection sensor (pad/mat) or internal element
Short to battery or ground in the sensor wiring
Faulty occupant classification module / SRS control module
Water intrusion or contamination in the seat cushion area

Symptoms

SRS/airbag warning lamp illuminated
Passenger/driver airbag enable status incorrect (airbag disabled when occupied or vice versa)
Seatbelt/occupant detection warnings or chime
Unable to pass vehicle inspection due to airbag fault
Intermittent faults that change with occupant weight or seat movement

What to check

Read and record freeze frame and stored SRS/occupant codes with a capable scan tool
Inspect seat cushion and underside for water, debris, or damage
Visually inspect seat wiring harness, connectors, and routing to body harness for pin damage, corrosion, or chafing
Check for recent seat/safety system repairs or aftermarket components
Perform wiggle test of harness and connectors while monitoring live data or DTC status
Compare live sensor data (occupancy/weight signal) from scan tool to expected behavior

Signal parameters

Typical system reference: 5 V reference supply to sensor; signal varies proportionally with occupancy (0–5 V range depending on design)
Open-circuit: signal may read near 0 V or OL/infinite resistance
Short-to-ground: ~0 V on signal line
Short-to-battery/over-voltage: signal >4.5 V or equal to vehicle battery voltage if protection absent
Sensor pad resistance varies by design (hundreds to several kilo-ohms). Compare to manufacturer known-good values

Diagnostic algorithm

Follow SRS safety procedures (battery disconnect and specified wait time) before disconnecting connectors or performing repairs
Use a scan tool to read DTC B12C7 and any related SRS/occupant codes. Record live data and freeze frame.
Visually inspect the driver seat cushion, underside, harness routing, and connectors for damage, contamination or water ingress.
With ignition ON (and following safety procedures), monitor the occupant sensor signal with a scan tool or multimeter: check reference voltage (5 V), ground continuity, and sensor signal voltage while seat is empty and with known weight placed on seat. Look for open/short indications or out-of-range values.
Perform a wiggle test of the seat harness and connectors while observing live data or DTC set/cleared behavior to find intermittent faults.
If wiring suspected, disconnect the sensor connector and check continuity and resistance between sensor connector and SRS/occupant module connector pins. Repair broken/chafed wiring, pins or connectors as needed.
If wiring and connectors are good, bench-test or replace the occupant detection sensor/pad per manufacturer procedure. Reassemble and reconnect.
If sensor and wiring tests pass but the fault remains, test/replace the occupant classification module/SRS control module following manufacturer diagnostic flow; module replacement often requires programming and SRS reset.
After repairs, clear codes and perform rechecks and a functional occupancy/airbag enablement test per manufacturer instructions.

Likely causes

Broken or pinched wire in seat-to-body harness (most common)
Corroded/loose connector at the sensor or at the SRS/occupant module
Failed passenger/driver seat sensor pad due to wear or moisture
Poor repair/installation after seat removal or airbag work

Fault status

⚠️ Status

B12C7 - Driver Seat Occupant Detection Sensor Circuit Fault: Indicates open, short, or out-of-range signal from the driver seat occupancy sensor to the occupant classification/SRS module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours