I have a '90 LS 400 with 160K miles. Maintain it myself with the help of genuine Lexus repair manuals. I read out the check engine error code and it displays a '25'. The book leads me to a whole lot of possible failing components. Does anyone have a hunch as to what is most likely to cause this problem?

 

Please check post "Trouble code# 25" on the SC400/300 Models forum.
Last time I checked it was on the secound page.
It should give you an idea on what could be causing this code.

Hopefully this will help,

Chris K
95 SC400

 

Follow your manual, there are three posibilities... check with a volt meter on E1, VF2, VF1, and TE1... My main O2 went on mine, $114 each, replaced both, I think left and right are different.

The manual show you how to check the voltage between .45V, so check on that, you will understand more once you check it.

the other problem might be TPS throttle position sensor, or MAF mass air flow, cheapest I know is $633, heard that some one can get it for $400

 

Lean malfunction code caused by a bad Oxygen sensor. Probably one of the main sensors. Get it checked out. Don't try to replace the sensor yourself. Many times they seize in the manifold. If you don't know what your doing, you might ruin the threads and need a new manifold.

Good luck.

 

I forgot, you need to buy a special tool to take the O2 out, it will take some sweat on your part but you can do it if you are careful. need to take some parts of the frame off to get enough room to get to the O2. If you don't have tools and rarely work on your car, then don't do it.

The old O2 sensors already have anti-seize on but it is very hard to take out... save money on my parts. Cost me $245 for the O2 sensors. Dealer will cost me $500 to replace the O2...

 

What happen?
Did you figured out what wrong yet?
Did you replace the O2 sensors yet?

 

The right main oxygen sensor was defective. I replaced both from Irontoad for $103 each and $8 shipping. Easy to do and takes an ordinary combination wrench #22. Problem was easy to troubleshoot, but I first went down wrong path because I didn't have good meter connections on check plug connector. Used anti- seize compound when installing.