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92 Ls400 Check Engine Code 12


hoffmanjp

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Hello,

I've got a trusty old 92 LS400 that has the miseries lately. Two days ago, I was driving it and noticed steam (smoke?) coming from under the hood about 1 mile from home. My wife asked what that nasty smell was. (It smelled like burning plastic or electrical smoke). I pulled over and opened the hood. There was still a bad smell and what appeared to be steam coming from the resevoir tank. I let it sit for 10 minutes, then drove it back home. I noted the temp gauge was normal at that time.

The next day I went out to try and find the problem and noticed the 2 cooling fans did not go on when the A/C was on. I got out the Lexus Manual and started troubleshooting that. I inspected the cooling fan relays and found then to look ok. Being an electronics tech in a previous life, I noted no burnt smells or components. I then disconnected the radiator temperature switch and the electric fans came on. Hmm.. Plugged it back in. I left the air off and added some coolant and noted the temperature in the normal range. I then took the car for a short spin and noted the temp running a bit warm. About a 1/4 mile from my house, the car just died. The engine turns over easily, but never starts or even tries to start. I pushed it back and let it sit overnight. This morning I read the manual and started troubleshooting the Check Engine lights. Got a Code 12. The manual says Cam position or Engine Speed sensors or ECU.

Are these symptoms just coincidence? Anyone have any ideas on where to start on this one? I still can't find the source of that burning smell.

Thanks in advance.

John Hoffman

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I would follow the lead of the underhood "steam" and presume that what you have is a coolant system leak. If enough coolant was lost perhaps this affected the water pump or sensors feeding the ECU. I would disconnect the battery in order to reset the ECU and then check for reported diagnostic codes.

If you have white smoke coming from the exhaust, you may have a coolant leaking through the head gasket.

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