camry p0171 with freeze frame data

This forum has been extremely helpful for DIYers like me. Thanks everyone.

This is probably a difficult one. I got the error code P0171 on my 2000 Camry, 4 cylinder. It translates into system too lean. I have not found any obvious vacuum leak. The freeze frame data reads:

DTCFRZF P0171
FUEL SYS1 CL
FUEL SYS2 N/A?
LOAD_PCT (%) 42.0
ETC (%) 169
SHRTFT1(%) 10.2
LONGFT1(%) 33.6
MAP (kPa) 12.1
RPM (min) 715
VSS(Km/h) 0
IAT(%) 54


I have erased the code a few times but it came back in a week or a day. When the code is there, I experience hesitation while waiting at traffic stops. This car was having rough idle at cold start but runs fine after warming up.

What could be the problem? This car does not have a MAF sensor, it has a MAP sensor.

Thanks very much for any advice.

1. Clean your injectors.
2. Check your fuel pressure at the fuel rail.
3. Check your Inlet air temperature sensor and engine coolant temperature sensor.
4. Could be your oxygen (A/F Ratio) sensor, bank 1 sensor 1 (on exhaust manifold, in front of cat converter).

http://www.automotiveforums.com/vbulletin/showthread.php?t=732698

Follow the troubleshooting procedure for this DTC in the FSM.

How shall I clean the injectors? Do I need to take it off the car and is it difficult to take off? Or can I just go to Jiffylube and let them do it?
Thanks.

Just put a can of Techron or similar solvent into a half tank of gas and drive it. If some of them were totally blocked, you would have to do something more radical, but since they work at least part of the time, you should be able to clean them easily (that is if they need cleaning). It's sort of a shot in the dark, but it's a cheap shot...

Wait until you use up all the gas before you make a judgement on the effectiveness.

Thank you very much, Brian. I just poured a can of Techron into the gass tank. Still don't know the result but will let you know. People from another forum suggested the MAP sensor reading is off, so I have bought the vacuum pump and will test the MAP sensor soon. The ECT (coolant temperature) and IAT sensor are easy to test, so I will test them too. I am also going to test the fuel pressure and replace the fuel filter if problems persist. With these diagnoisis planned, it sounds stupid to replace the AF sensor blindly, but unfortunately I have ordered it from Ebay. I will update what I found. Thanks a lot.

I have tried Techron but the code still came back. There is a second code P1130 which I may have missed earlier. I have tested the MAP sensor , the ECT sensor, the IAT sensor, they all read good. The OEM air fuel ratio sensor went bad about 3 years ago and I replaced it with a NAPA part. It might have failed. I ordered an OEM part and will see if it solves the problem. Thanks.

Check the fuel pressure

Fuel filter replacement and fuel pressure are in the plan if the new af sensor does not cure it. Thanks.

I replaced the AF sensor. It has been several days and the code hasn't come back. The car is very smooth now, even the rough idle at cold start disappeared. I think the problem is fixed. Thanks everyone.

I replaced the AF sensor. It has been several days and the code hasn't come back. The car is very smooth now, even the rough idle at cold start disappeared. I think the problem is fixed. Thanks everyone.

I hope you are right but your symptoms certainly did not indicate a faulty A/F sensor.

P0171 is a very inexact code for troubleshooting purposes - at least in a Toyota. This code gave me some trouble a few years ago and I ended up bringing it to the attention of a shop foreman at my local Toyota dealership. My discussion basically represents the feedback I received from him.

Yes, Brian, and you pointed to the right direction. Thanks.

So three things have been done besides all the tests:

replaced air filter,
used two bottles of Techron,
replaced AF sensor.