B2345: Seat Switch Reference Voltage Negative Common Open Circuit

B2345 is set by the body control module (BCM) when it detects an open circuit in the negative common reference line for the seat position switch assembly. The seat switch bank -- which controls fore-aft, height, tilt, and lumbar adjustments depending on vehicle spec -- shares a common reference voltage and a common ground return. If that ground return circuit is broken, the BCM can't read any switch input and disables all seat motor functions. The powered seat will not respond to any adjustment until the circuit is restored.

The most common physical cause is a broken wire in the seat harness. Seat harnesses are subjected to constant flexing as the seat moves forward, back, and up, and as occupants get in and out. Over time, the wires inside the insulation can fatigue and fracture internally while the outer sheath remains intact, making the fault invisible to a visual inspection. Corroded or contaminated connectors underneath the seat are the second most common cause -- the under-seat area is exposed to spilled drinks, mud, and floor cleaning, and moisture in the connector block will corrode the ground pin over time.

To diagnose, move the seat to its full forward or back position to relieve any tension on the harness, then probe the negative common circuit at the seat connector and at the BCM. Continuity between those points with the circuit unpowered will confirm the fault location. Harness repairs in this area are typically straightforward once the break is located -- the harness length allows enough slack to cut, splice, and re-insulate without replacing the entire loom.