43-1X: Left Side Sensor No Signal

Circuit fault

What 43-1X means

Side impact sensors report to the control module over a wired connection, and the module expects to hear from each one on a schedule. Silence from the first left side sensor produces 43-1X. A missing signal can come from a break in the wiring, a connector that is not making contact, or a sensor with no power, and the module cannot tell those apart from where it sits.

These sensors mount low in the body structure, often at the base of a pillar or inside a door area, where they can feel a side impact immediately. That location puts them near door seals, sill drains, and carpet edges, all of which are places water ends up. A wet connector will interrupt communication long before anything corrodes visibly.

Common causes

• Water at the pillar or sill connector interrupting the sensor circuit
• A connector partly unlatched after door, trim, or seat belt work
• A broken conductor in the floor or pillar harness from crushing or a trim fastener
• A sensor that has lost its power or ground feed at the connector
• Corroded terminals in the sensor connector after a wet carpet went unnoticed

Crash data or hardware fault?

43-1X describes the circuit as it stands right now, which makes it a live fault instead of a deployment record. Restore the connection and the module hears the sensor again on the next key cycle. Crash data is written once when the system fires and cannot be erased by any scan tool, no matter how the wiring reads afterward.

Does our reset clear it?

A reset is not the answer while the sensor is silent, since the module will find the same silence at its next check and store 43-1X again. Repair the wiring or the connection first. Our mail-in module reset addresses a module locked on crash data after a deployment, which is a different fault living in a different part of the module's memory.

Which makes throw it

Honda and Acura both list 43-1X for the first left side impact sensor. The definition and the diagnostic path are the same on either badge.

What to do next

Get to the sensor connector and unplug it, then look for moisture, green terminals, or a latch that never closed. Check for power and ground on the harness side before you condemn the sensor, because a sensor with no supply cannot answer the module. If the feeds are good and the wiring reads clean end to end, the sensor is the part, and we stock genuine OEM Honda and Acura side impact sensors. Related codes: 42-2X, 43-2X, B1B09.