00656: Passenger Occupancy Sensor G128

Hardware fault

What 00656 means

The occupancy sensor sits in the passenger seat cushion and tells the controller whether the seat is occupied. That answer decides whether the passenger airbag is armed, so the controller treats a bad reading as a reason to flag the system. When G128 reports a fault or an implausible value, 00656 goes into memory.

These sensors are built as a mat or a pressure element inside the cushion foam, connected by a short harness to the connector under the seat. Everything about that construction is vulnerable to use. Years of people sitting down, cargo dropped on the seat, and child seats cinched down tight all flex the element, and the under-seat connector corrodes like every other one in that area.

Common causes

• A damaged occupancy mat inside the cushion after years of use or heavy loads
• Corrosion in the connector under the passenger seat
• A pinched or stretched sensor harness from seat travel
• Damage from a child seat base tightened hard against the cushion
• Liquid soaked into the cushion reaching the sensor element

Crash data or hardware fault?

00656 is a hardware and signal fault the controller is reading right now, not a stored crash record. Repair or replace the sensor and the fault stops being reported. Crash data is written into the controller at deployment and locked there, and no amount of seat work touches it.

Does our reset clear it?

There is no reset that repairs a mat inside the seat cushion, and the controller reports 00656 again as soon as it reads the sensor. Handle the sensor or the connector first. Our mail-in reset is the right service for a controller locked on stored crash data, which is a different condition altogether.

Which makes throw it

G128 is the occupancy sensor on Audi and on Volkswagen alike. The sensor location and the failure pattern are the same across the two brands.

What to do next

Check the connector under the passenger seat before you open up any upholstery, since corrosion there is easier to find and far cheaper to fix than a cushion mat. Wiggle the harness through the full range of seat travel while watching for the fault to come and go. If the connector is clean and the harness is sound, the sensor element inside the cushion is the part, and it means taking the seat cover off to reach it. Related codes: 00655, 01025, B1342.