I was getting poor mileage the last couple of tanks of gas and the check engine light came on. I took it in for service and was told that the engine is running rich due to a malfunction with the onboard computer. Lexus has no fix for this and doesn't expect to have one until April at the earliest. I got about 17 mpg on my last two tanks vs. 22 - 24 normally (not much highway driving for me). So it looks like I'm stuck with a 20%+ decline in mileage for the next 3+ months. Has anybody else seen this problem?

 

I haven't hear of this problem before, so they (dealership) won't replace your computer?? April is a long way's off.

 

Maybe he's saying the new ECU wont be in until April?

 

Actually, they already replaced the computer - just two months ago. They also had to replace two oxygen sensors at that time. April IS a long time to wait, so I've been in touch with Lexus Customer Service for restitution.

 

Usually if this would be a wide spread issue related to ECU module across all GS300 models, they would issue TSB (technical service bulletin publicly available to everybody). Maybe it is an isolated issue with your car and they are just waiting for a module from Japan?

 

Nope...same issue here - they claim it was already a TSB that has additional issues in the ECU program that go beyond the TSB indicated oxygen sensor type replacment... now it's a fuel mixture sensor or something like that, but that didn't resolve it for me as I didn't need the TSB - new sensor already installed. I just need to wait.

Lee

 

Eh. I get 16-18mpg ALL the time. No flooring it at all. I've driven at least 1k miles on teh car now with about 6-7 gas fills. Best one I got was 21mpg. Worst was 16.1. Average is about 17.5 mpg.

 

It is a issue for all GS and some IS owners. Check out the IS forums and you will see it happens to them also a lot. If you open up your oil cap just smell it you will notice it smells like gas. Also look at your exhust pipes you will see that they are black. This is all because they all run rich. Now the reason why it only happens to a few owners is because if you drive the car more then 10 miles a day the gas in the oil is mostly burned off and the problem doesn't happen. However if you only drive the car a little bit and not often more and more gas build up in the oil and there is no way for it to burn off causing the 0'2 sensor to go off and check engine light. There have been a lot of TSB's on this but they haven't come out with a fix yet. It was the way the enigne was designed they never thought owners would drive short distances.

 

really? so since I drive about 5miles one way everyday, my gas runs richer than it should? If this is the case for mine (my exhaust tip is black, but so is my other cars I had) and the check engine light does go on, is this covered under warrenty?

 

Purebliss - I presume you're being funny... right?

All - My AWD GS350 is averaging 16-17mpg in city driving of about 12-20 miles per day. My car has 4,000 miles on it and I was planning on having the dealership look into this when I took it in for the first free 5,000 mile oil change. I'll check it tonight for the warning signs mentioned previously.

Thanks

 

Nope thats what I was told and they worried because the new LS is using bascially the same design it it.

 

MCin STL - What dealership did you take your car to and are you driving a RWD or AWD? My gas mileage is similar to yours and I've got the 07 AWD. One last question, when its cold (say below 20F) is your engine idle running high (+8000 RPMs) longer (a good 5-10 minutes after the engine temp guage says that the engine has warmed up) than you'd expect?

Thanks

 

if you drive a short distance like, 10 times in a row, it will throw the code. mix in some longer drives at least once a week and the problem should go away.

 

does this apply to all lexus vehicles or only the gs?

 

i personally know of only one case involving one of my customers that owns a gs, no other cases thus far