Lexus IS passenger seat failure

Greetings. I had a similar situation with my Lexus IS. The symptoms strongly indicate a battery issue. A discharged or defective battery can cause electrical gremlins, including problems with the electric seats. The seat motors need sufficient voltage; if the battery can't provide it, the seat will fail and an error code may be stored. Have you load tested your battery recently?

Thanks! I haven't load tested the battery, but the car starts fine and I haven't seen other electrical issues. Could a slightly weak battery really cause just the passenger seat to fail? Seems odd that the driver's seat is working perfectly. Any tests I could do myself?

While the vehicle may start without issue, the voltage drop during operation of high-current devices can be significant even with a slightly weak battery. Given that the diagnostic system has already registered an error, it would be most prudent to consult a qualified automotive electrical technician to perform comprehensive diagnostics. It is possible the problem stems from the seat wiring, the motor, or indeed a weak battery. However, professional diagnosis will be more economical in the long run, rather than replacing parts speculatively.

Thanks for the detailed advice. I took it to a workshop, and you were spot on – it was indeed the battery! Apparently, it was causing a voltage drop specifically affecting the passenger seat circuit. New battery fitted and all working perfectly now. Total cost was 290€. Cheers!