92 Ls400 Check Engine Code 12

[hoffmanjp]

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

[92Lex]

If it was a speed sensor the D4 should flash...Im leaning more towards the CMP, maybe your timing belt slipped a tooth. Check your timing.

[smithm92]

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.

[99lsguy]

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

Agreed....

check your oil cap too. If it has a milky film under the cap, then the head gasket is failing.

[hoffmanjp]

Yep, It's the timing belt. Took off the covers and it's shedded. Also this is where the burnt smell came from. FYI Got 137K out of the belt.

Looks like a weekend job.