GX Transmission Issue

Hey, I'm having a weird issue with my 2004 Lexus GX, gasoline engine. It's got about 124k km on it. The transmission is acting up – shifting feels all wrong, the trans indicator light is on, and sometimes it just doesn't shift properly, like it's stuck in emergency mode. I was reading undervoltage can cause this? Anyone seen this before?

4 comment(s)

Dude, I had something similar happen on my GX. Implausible shifting behavior. Check your battery and alternator first. Low voltage can mess with the electronic controls in the transmission. Have you scanned it for codes? What codes are popping up?

Yeah, I scanned it. It threw a code related to the transmission fluid pressure, but the fluid level seems okay. You mentioned low voltage... did that actually fix it for you? And how did you diagnose it?

It did. The tranny was basically in limp mode. I checked the battery voltage and it was low when the engine was running, so replaced the alternator. That fixed the voltage issue. I still recommend going to a workshop to get it checked.

Thanks for the tip! Turns out it WAS voltage-related. I took it to a workshop, they checked the wiring and found a bad ground. Cleaned it up and everything's back to normal now. Cost me 240€, but way better than a new transmission. Appreciate the help!

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