i am getting an error code # P0171 on my es300 any suggestion what this is

P0171 = System Too Lean (Fuel Trim)

any suggestions on what i should do to fix it

lexus300aa, you are double posting you quesitons and that is going to get confusing for everyone.

Here is the my responce to this question from the other thread.

P0171 is System too lean, (Fuel Trim) bank 1.

Here are your trouble areas:
-Air Intake hose, loose or cracked
-Fuel line pressure
-Injector blockage
-Open or short Air/Fuel sensor circuit
-Intake air flow meter
-EFI engine coolant temperature sensor
-Gas (exhaust gas not fuel) leakage on exhaust system
-PCV hose connection

hope this helps.

steviej

Stevej----How or where do you find all the things that could be wrong per each code?

example is code p0171 and you listed some areas to look at....

my 2002 ES is about to come out of the 4ys/50k mile warranty.
I indulged in the 2 volume set Lexus shop manual.

The suspect areas are what are listed for each code. Year doesn't matter on most of the codes because the codes are for the 1MZ-FE.

steviej

I was getting a P0171 system too lean and a P0401 EGR insufficient flow error. This was driving me nuts because it was causing my car to shake while stopped and at times it even stalled on me. I checked all the vacuum hoses for leaks and changed the EGR vacuum modulator like is recommended on this site but still nothing. I was finally taking out the MAF sensor to clean it out and found the problem. It wasn't the MAF sensor but the air intake hose. It had a crack on it and when I took out the MAF sensor out it cracked all the way through. I replaced the air intake hose and my car is running like new and I'm not getting anymore check engine lights.

EGR

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor. Clean the MAF Sensor with the correct spray solvent. Click CODE PO171

I had the same problem with my 2000 Lexus ES300: check engine light + trac off light. The ODBII read read P0171. I failed inspection and the repair shop changed the front two O2 sensors for $500 and still the lights came back on. They managed to clear the codes and drive it for a couple of hours and passed inspection finally, reluctantly. Still they wanted to change the rear O2 sensor and maybe the two catalytic converters. I was having none of that. Anyway, immediately, the engine and trac lights returned! That was last year and I've been driving with the lights the whole time.

This year, with the inspection upon me, i got help from a friend who trolled the Lexus owner blogs and found some tips. Instead of changing the rear O2 sensor as the repair shop had suggected, we decided to take apart the air filter and inspect the mass air sensor. Behold! there was lint collected on the two wires and the tear drop thingamajig (not sure what it is). We cleaned them with a couple of swabs (at a cost of $0.05) and put the air filter assembly back and cleared the codes... it's been 3 weeks and the check engine and trac lights have not returned...