B1B88: Seat Weight Sensor 1, Low

Circuit fault

What B1B88 means

Sensor 1 handles the right rear mounting point, the outboard corner behind the seat cushion. The occupant classification module supplies that circuit and measures the signal coming back, expecting it to stay inside a fixed electrical range regardless of whether anyone is sitting there. B1B88 is stored when the value drops under that range.

Weight sensing is what tells the system whether the passenger airbag should arm for an adult, hold back for a child seat, or stay off for an empty seat. One corner reading low removes the module's ability to make that call, so it flags the fault and turns on the airbag warning lamp.

Common causes

• A right rear sensor connector loosened or corroded under the seat
• Harness damage from items stored under the seat rubbing against the wiring
• A failed sensor that no longer produces a usable output
• Improper reinstallation after seat work, leaving the sensor loaded or bound
• A short to ground somewhere in the sensor input circuit

Crash data or hardware fault?

Circuit codes report what the module measures at this moment, so B1B88 tracks the actual signal on the sensor line. Crash data is a permanent record of a deployment that already occurred, written once into module memory and immune to scan tool clearing. The two are handled in completely different ways.

Does our reset clear it?

A reset does not correct a low reading at the right rear sensor. The module will measure that input again within seconds of the next startup and store B1B88 once more. Repair the circuit first, then run the occupant classification calibration. The mail-in reset we offer is aimed at modules holding crash data or a stored internal fault.

Which makes throw it

B1B88 comes up on Chrysler vehicles in our lookup, on the four corner passenger seat weight sensing system.

What to do next

Clear out whatever is stored under the passenger seat and inspect the harness at the right rear mount, because crushed wiring there is a frequent cause. Check the connector pins for corrosion, then test the sensor and the wire back to the module separately. After the repair, complete the calibration procedure so the system starts classifying the seat correctly again. Related codes: B1B83, B1BA6, B1B55.