bachlauter

Hi there..
My MIL came on--Check engine and trac off. I had the code read and got po171.(bank 1 sensor 1 fuel trim lean) By the way I have a 1999 es300 with 110,000 miles. I first changed the air filter and tried some fuel injector cleaner. I replaced bank 1 sensor 1 oxygen sensor, the hard to reach one near the firewall. I also replaced the MAF. All of this time, I was having no real symptoms that were affecting drivability, I just simply wanted those dash lights to go away! Well, all of a sudden I am having very strange running problems. Occasionally, and NOT related to cold start, the car will not shift out of 3rd gear. When I try to drive 70 mph, the car just winds out to 4000 rpms and makes me very nervous. Interestingly enough, today for example, I start out driving thru town and the car runs great, as I leave town, the car shifts normally, normal rpms and when I get out on the freeway, perfect. However, when I take the exit and come to a stop and then pull out again, onto a 70mph road, the car will not shift past 3rd gear. The car is clearly fully warmed up.
I can't figure out how this diagnostic code would have anything to do with the transmission.
Also, as I have replaced the previously mentioned parts, I have disconnected the battery to remove codes and MIL, but the MIL always comes back on.
What to do next? The shifting problem is weird, but is definitely an intermittened problem. If I have the option at high speeds and can pull over and turn the car off, it has (so far) always shifted normally again once I restart and drive again.
Any thoughts would be appreciated!
~Christy

exxonham

Not sure about the Transmissin issue, actually have no idea, but ive had that code few times in my 99 but if you do a little search many and many of ppl have had that same prob, with many different results but isent the bank 1 sensor 1 the o2 sensor the one you see right when you open the hoodright off the intake?

Acording to repair guide- Sensor 1 refers to the sensor closer to the engine body.

Sensor 2 refers to the sensor farther away from the engine body.

so try that and if you replaced MAF Air filter than try testing the sensors before you change them.

And this copy paste from Lexus Repair guide might help little

DTC No. DTC Detecting Condition Trouble Area
P0171
When the air fuel ratio feedback is stable after engine warming
up, the fuel trim is considerably in error on the RICH side
(2 trip detection logic)

Air intake (hose loose)

Fuel line pressure

Injector blockage

Heated oxygen sensor (bank 1, 2 sensor 1) malfunction

Mass air flow meter

Engine coolant temp. sensor
This is all it can be and as far as trans issue Hell if I know my 99 es trans does its own thing sometimes like all my interior and outside light flicker every few days signiling prob alternator going bad but the trans jumps little ONLY when the lights flicker, just totally beats me but car is still fine but hope this helps

bachlauter

Thanks for the reply..
Ok..I went ahead a replaced the Oxygen sensor near the radiator side of the engine. Unfortunately, it didn't fix the problem, as the Mil came back on.
So...the strange thing about the transmission problem is that it enters a fail-safe mode. BUT if I stop and turn off the engine and restart, then it will operate normally. I'm interested in the engine coolant temp. sensor. Could you tell me more about that? My dash gauge reads normally. I read somewhere that a stuck thermostat could cause such a problem, but my heater blows hot.
Doesn't it make sense that the engine is telling the transmission the wrond thing, and the transmission won't advance past 3rd gear? I don't think I have a fuel problem, as the car doesn't sputter and gets plenty of fuel. In face, it idles nice and low and smooth. The thing thats got my puzzles is how po171 and the transmission are related.
Could it an ignition switch problem? Could driving it so long with this fuel trim lean condition have dupmped so much fuel into the engine by overcompensating that now I have gummed up spark plugs?
My atf is full and clean btw.
~Christy

PFB

The transmission has its own separate temperature sensor.

bachlauter

Ok dumb question, but does the transmission have it's own diagnostic plug for a obd tool?

Coulter

I think the smartest thing would be to pay a dealer or reputable shop to do a diagnostic scan to pinpoint the problem. I've also been guilty of "shotgunning" parts at a problem, but it can get expensive in a hurry.

You've spent about $500 in parts so far (if you're using OEM parts) and it still hasn't resolved the issue. A dealer has expensive diagnostic scan tools that go far beyond just a simple OBD code. A $100 diagnosis would save you a lot of money and headaches, you can then do the work yourself.

Also might want to check your fuel filter and see when the last time it was replaced, it could be insufficient fuel pressure, and that is a part that needs to be replaced anyway is it's been neglected.

bachlauter

Update...
I finally ordered a obd tool. I was going on what auto zone was telling me and the when I stopped by after that new O2 sensor was put on, they claimed to have loaned out the tool. Whatever.
Anywho...with my new tool, I got one trouble code...p0330 which makes total sense because of the whole fail safe nightmare! The other code, p0171 didn't show up, so maybe that O2 sensor cured that problem!
So now I' looking at a short in knock sensor 2 circuit, replacing knock sensor 2 or the ECM.
What's up with the ECM?
~Christy