Lexus RC Poor Starting

I'm having a real head-scratcher with my 2018 Lexus RC, gasoline engine. I've got about 225433 km on the clock, and lately, it's been starting poorly. I scanned it, and it's showing "Terminal 30 continuous plus interrupted." I'm guessing this refers to constant power, right? I checked the battery voltage, and it seems okay at rest, but during cranking, it dips pretty low. Could a heavily discharged or defective battery cause this? I've also been reading about potential issues with the circuit breaker, ignition switch, and fuse box. Is there anything else I should check before tearing into it? Could a short circuit somewhere be draining the battery even when the car is off? I'm not sure where to even start looking for a voltage drop!

4 comment(s)

Hey there! I had a similar issue with my older BMW 3 series a while back. It was driving me nuts! Same symptoms – slow starts and a similar error code relating to the constant power supply. Did you check for parasitic draw? Meaning, is something pulling power from the battery even when the car is off and everything is supposedly shut down? In my case, it ended up being a faulty module that wasn't fully powering down. That constant drain eventually killed the battery. Have you tried disconnecting the battery overnight to see if it holds its charge? That could help rule out a bad battery.

Thanks for the quick reply! A parasitic draw... that's a good point! I hadn't really considered a module not shutting down properly. How did you pinpoint the faulty module in your BMW? Did you just start pulling fuses one by one to see when the draw stopped? And if the battery holds charge overnight when disconnected, that pretty much confirms the battery is okay, right? I'm just trying to get a better handle on the troubleshooting process before I start randomly replacing parts.

Yep, exactly! Fuses are your friend here. That's precisely how I found my culprit. I used a multimeter to measure the current draw at the battery while pulling fuses one at a time. When I pulled the fuse for the faulty module, the draw dropped significantly. And yes, if the battery holds its charge when disconnected overnight, it's a strong indicator that the battery itself is fine and that something is draining it when connected. Honestly, given that it's a Lexus and you're not super familiar with electrical gremlins, might be worth getting it checked out at a reputable shop. Electrical problems can be a real pain to diagnose without the right tools and experience.

So, it turns out it was indeed a bad battery, even though it seemed okay at rest. Took it to my local garage, they confirmed the battery was heavily discharged and defective. They replaced it, and the starting issue is gone! Total cost was 290€ I really appreciate the help!

Join the discussion now: