B1650

Symptoms

• Airbag/SRS warning light stays on continuously while driving
• passenger airbag OFF indicator stays on even when a full-sized adult occupies the seat
• passenger airbag is disabled while the code is active.

Probable causes

• 1) Damaged under-seat wiring harness or connectors (most common). 2) Failed seat sensor mat - the pressure-sensitive pad in the passenger seat cushion can be damaged by age
• liquid spills
• or kneeling on the seat. 3) Lost or failed zero-point calibration of the OCS (e.g. after seat removal/reinstallation or battery work). 4) Improperly reinstalled seat
• aftermarket seat covers
• or seat heaters interfering with the weight readings.

Diagnostic steps

1. Read the SRS sub-codes with a bidirectional scanner capable of accessing the airbag module (basic code readers cannot read or clear B1650).
2. Inspect the under-seat wiring harness and yellow SRS connectors of the passenger seat for damage, corrosion, or loose connectors; repair as needed.
3. Check for causes of bad weight readings: aftermarket seat covers, objects wedged in the seat, a seat that was removed and reinstalled incorrectly.
4. If wiring and seat check OK, perform the OCS zero-point calibration with an empty passenger seat: vehicle on a surface inclined less than 1 degree, seat in neutral position (fully rearward, seatback upright, headrest at lowest setting, seat height at lowest if equipped); on Toyota this requires Techstream or an equivalent scan tool (a jumper-wire method via DLC3 terminals Ts and CG is also documented).
5. If calibration fails repeatedly, suspect a failed seat sensor mat or OCS ECU and replace the faulty component, then recalibrate.
6. Clear codes and confirm the airbag light goes out and the passenger airbag indicator behaves correctly with the seat occupied and empty. Do not drive with an active B1650: the passenger airbag is disabled.