Câblage endommagé sous les sièges avant

The looms running beneath a vehicle's front seats, and one of the most consistently abused wiring locations in any car.

Three things concentrate there and no other part of the interior gets all three. The harness flexes every time the seat slides fore and aft — thousands of cycles, in a bundle that was routed for a fixed position and then asked to move. It sits at floor level, where feet, luggage, dropped objects, grit and spilt drinks arrive, under a carpet that hides all of it. And its connectors are unplugged constantly for unrelated work — carpet, floorpan repair, trim, sound systems, retrofits — because a seat is the thing that has to come out to reach the floor.

What runs through it raises the stakes above comfort. Seat adjustment and memory, yes — but also seat heating, occupant classification for airbag deployment, seatbelt buckle switches and side airbag circuits. So damage here can produce an airbag warning light rather than merely a seat that will not move, and that changes how urgent it is.

The characteristic fault is intermittent before it is permanent, because a partly broken conductor or a corroded pin makes and unmakes contact as the seat moves — which is also the free diagnostic: a fault that changes as the seat is slided forwards and back is this.

Refitting is where much of the damage is done. A loom pinched under a seat rail as the bolts are tightened, or a connector left unmated in a space nobody can see, is an ordinary outcome of a job that had nothing to do with the seat. A code appearing after any interior work is that until shown otherwise.