B2-1X: Rear Safing Sensor No Signal

Circuit fault

What B2-1X means

A safing sensor confirms that a real impact is happening before the module commits to a deployment. Honda places this one under the rear seat cushion, wired back to the SRS unit. When its reports stop arriving, the unit has lost half of the agreement it requires and records B2-1X.

The location explains most of the failures. Rear seat cushions come out for fuel pump access, child seat anchor work, and cleaning, and the sensor connector underneath is easy to leave unplugged. Rear floors also collect water from door seals and trunk leaks, which corrodes the connector sitting right there.

Common causes

• Rear safing sensor connector left unplugged after rear seat cushion removal
• Corroded connector pins from water sitting in the rear floor pan
• Harness pinched or crushed when the seat cushion was reinstalled
• A failed safing sensor that no longer sends a signal
• Loose sensor mounting bolts leaving the sensor not solidly attached to the body

Crash data or hardware fault?

Count B2-1X as a live input fault, checked by the module every time the system powers up and stored only while the signal is missing. Crash data is the permanent record a module writes after a deployment, and a scan tool cannot erase that. Restoring the sensor signal takes care of B2-1X by itself.

Does our reset clear it?

Do not order a reset expecting it to fix a missing safing sensor signal. Our service restores modules that are locked on crash data after a deployment, which is a completely different problem. Reconnect or replace the sensor first. If the car deployed and the module is also holding that event in memory, mail it to us when the repairs are done.

Which makes throw it

Honda is the make that reports B2-1X. It is one of the letter-prefixed Honda codes, and the second pair narrows the exact condition the unit found on the rear safing sensor circuit.

What to do next

Lift the rear seat cushion and check whether the sensor is plugged in and bolted down, because a cushion that went back in over a loose connector is the usual history behind this code. Look for water staining in the floor pan at the same time. If the connection is clean and tight, the safing sensor itself is next, and we stock genuine OEM Honda SRS sensors. Related codes: B1057, EX-11, 31-3X.