p0171 tried everything!! ????

[tommy77]

I have a 1998 camry le 4cyl. p0171 code show up. It's a california emi. car, and I think i tried everything. check the front a/f sensor,in spec. Checked the MAP, in spec. Check fuel pressure, in spec. Inspected all hoses for cracks, there is none. Please anyone!!! any ideas would be appreciated!!

[joede]

obstruction in the injector? Heated oxy sensor malfunction? ECT sensor malfunction?

[tommy77]

I will try that to test that ECT sensor next, didn't know that it would throw that code. THANKS

[fenixus]

tommy77, any chances you ran out of fuel recently ? they could have triggered the code (System too lean), if so just disconnect battery for 1 minute (or remove 15A EFI fuse instead) to reset the ECU.

more on P0171/P0172 here:
http://www.camrystuff.com/manuals/Gen4/Diagnostics.pdf
page 84.

Possible trouble areas:
-Gas leakage on exhaust system
-Air intake (hose loose)
-Fuel line pressure
-Injector blockage
-Heated oxygen sensor (bank 1 sensor 1)
-Manifold absolute pressure sensor
-Engine coolant temp. sensor

You may have leaks on the intake vacuum or one of vacuum hoses around engine (EGR system) is leaking vacuum.
Does the engine run rough at idle ? your fuel injectors might be clogged/dirty, so ECU is administering much more fuel to keep system running closest to ideal theoretical value. when have you replaced the fuel filter last time ? have you tried adding Chevron Techron to tank ?

have you checked your flex pipe for cracks ? that would be an exhaust leak tricking your rear o2 sensor to report false values to the ECU.

you may need some obd2 scanning tool which will show you fuel trims at different conditions. also such tools could tell you under what conditions the code was triggered (reading the Freeze Frame).
it would also tell you what other (also pending) codes you may have. or you would be able to watch o2 sensors voltage outputs and seeing much more live data from ECU.

[fenixus]

another possibility is that your EGR valve cannot fully close and stays a tad open at idle (while it should be closed). so you may need to unbolt it (easier to do together with bottom exhaust pipe). it can be caused when the valve inside is dirty with lots of carbon deposits.

clean it with sea foam. check the DIY in FAQ section.

if you decide to unbolt the bottom exhaust pipe I have to warn you, those 10mm bolts are VERY poor, i broke one of them and failed in removal of leftovers. long story short, no one and nothing could remove the broken piece and valve got destroyed in process, had to order new one ($130 OEM new from online dealer).