Well I've been getting this combination. I've read so many posts that it's only gotten more confusing. I've only found this combination in one other post but no solution. It would be nice if it was as easy as cleaning the MAF and I'll try that first. But anyone remember if it would still be covered by the dealer under emissions? 2001 RX300 62,000mi first sold Dec 2000. Can anyone point me to the right components? All started with an oil change and new air filter. I’ve checked the small vacuum hose after changing filter. The CEL lights have been reset several times over 3 weeks and come back after a while. Sometimes 10 miles sometimes 250 miles before they reappear.

 

1. Check and replace your Engine Air Filter.
2. Clean/replace your MAF sensor (read other threads on how to do it).
3. Reset codes.

This is strange that you are getting P0174, I thought Toyota was only using P0171. Do you have any pending codes? If you have any for these: P0125, P1130, P1135, P1150 or P1155. You need to check your A/F sensors.

 

Thanks. Those were the only codes that were in the system. I did take the MAF off and cleaned it well this morning. It's a brand new air filter and triple checked to make sure it was in and air box is locked down correctly. I'll test drive later today but some times it takes several days before the cel light comes back on.

 

What is your current MPG?

 

You are right, there is no P0174. Checked my entire manual just to be sure. Incidentally, I got a P0171 on the expressway this morning. Very hot weather, moderate, but moving traffic, and shazzam, CEL. I ended up pulling out my scanner and reseting it right on the highway.

I have come to a theory that some of these P0171 and even A/F sensors (dead or giving strange readings) could be due to them getting old AND the fact there are precats positioned right after. I have been reading on Solaraguy.org intently on this subject and even asked a few members, and they don't get these codes as often. Keep in mind that MOST of the Solaras there are without the precats (non Calif. spec) and I have hunch that the combustion process makes just before the precat and right around there the two A/F sensors are an absolute oven compared to other parts of the exhaust system.

 

Still around 22-23 highway.

If there is not supposed to be a P0174 then I'll take it back to Auto Zone if the CEL comes back on and make them show me when they read it this time.

It did seem to only do it when is very hot outside. 90-100f. at 5000ft and above normal acceleration.

 

I am at 7,000+ feet and the effects of heat can get significantly magnified at altitude. I am sure the design of my intake modification (took more hot engine air in abundance) no doubt had an effect. I changed my intake today (thread upcoming) so we will see if that has an effect in these hot summer months.

 

i gotz a 2002 lexus rx300 diagnostic pdf file thats say P0174 system too lean (bank2)

Areas to check:
-Air Induction System
-Injector blockage
-Mass air flow meter
-Engine coolant temp. sensor
-Fuel pressure
-Gas leakage on exhaust system
-Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
-A/F sensor (bank 1, 2 sensor 1)
-ECM
-PCV piping

 

Wow, my volume 1 1999 manual shows nothing, but as I have found out the later manuals are much better updated.

 

This it looks like I'm on the right track so far. Start with the easy stuff and eliminate those things first. Code hasn't come on again yet after cleaning the MAF but it was cool this morning. I'll try to make it come on with WOT on the way home in the heat. I worry that the O2 sensor got bumped during the oil change.

 

The way I sometimes try to force the P0171 is to hit WOT, above 40 mph then slow down on the brakes about half way, causing a shift in the air coming in. Works better to force this with hotter weather.

 

I think 2001+ have separate lean/rich codes for each bank.

 

Still no codes after 2 days of driving. But it took a week one time for it to come back. I'll give it a tank of gas and if it hasn't come back I'll let everyone know if the MAF cleaning fixed them problem. I may also dump some additive in the gas to help clean the injectors.

 

Well after 2 weeks of driving the CEL codes have NOT returned. Just a dirty MAF and cleaning it solved my problems. guess the combination of dirty air filter and dirty MAF let the computer think everything was just fine. Changing to a new air filter and still dirty MAF the computer thought it was getting too much air and thus a lean condition.