NX seat heater failure

I recall facing a comparable problem with the seat heating system in my previous 2014 Volvo V60. The symptoms you describe, specifically the lack of heat and the presence of an error code, strongly suggest a failure within the heating element itself or potentially a related thermal sensor. Did the error code provide any further detail? For example, relating to resistance or open circuit.

The error code, unfortunately, isn't very specific; it simply indicates a general malfunction within the seat heating circuit. I haven't measured the resistance of the heating mat yet, but that's my next step. In your case with the Volvo, was the error code equally vague, and how did you ultimately diagnose the problem?

Indeed, my Volvo's diagnostic code was rather uninformative, similar to your Lexus. After some investigation and consulting with a technician, the consensus was a faulty heating element within the seat. Considering your Lexus' age and mileage (165213 km), a heating mat failure is plausible. I would advise consulting a qualified workshop, since accessing the element means disassembling the seat.

I suspected that a workshop visit would be necessary. I've taken it to a trusted mechanic, and as suspected, the heating mat was indeed defective. Repair cost 390€.