I have a 99 Accord LX w/ 105k miles. I have done some research on this code but I havent found any real good advice. The CEL code comes up P0171...fuel system too lean-bank 1... The best advice I've found so far is O2 sensor or possibly fuel filter??? My question is what to do first? Is there any way to check the O2 sensor or should it just be replaced? Also, which O2 sensor would need to be replaced? I'm assuming the pre-cat one at the manifold but I don't want to assume. Any advice or similar problem/ fix would be greatly appreciated....Thanks

Bump for some help please...

12. How do I pull my engine codes if I do not have a scanner tool?

Do one of the following:
a. Go to Autozone and have them read your codes (it's free)
or
b. See the instructions below
WARNING!!!: USE AT YOUR OWN RISK AS SHORTING THE WRONG PINS WILL RESULT IN DAMAGED ECU.

a. Find the Data Link Connector (DLC) located under the instrument panel in the driver's side. It is bolted to the kick panel and is gray in color on the 1998 models.
b. Jump terminals 8 and 13 by connecting them with a wire/cable. ...............________
...._____|________|_____
.../|1...2...3...4...5...6...7...8|\
../.|==============...|.\
./..|9.10.11.12.13.14.15.16.|...\
/----------------------------------- \

DATA LINK CONNECTOR (DLC)


c. Turn the ignition key to ON and observe the "CHECK ENGINE" light. It will flash the trouble codes. For example: 2
long flashes, pause and then 3 short flashes = 23 = P0325 = Knock sensor circuit fault (4 cyl only).
One short flash = 1. One long flash = 10. If there is no trouble codes, the light will not flash.


Flashes.....Code(s)............................... ..........Description
1...............P0131,P0132....................... .........Primary heated O2 sensor (http://www.honda-tech.com/zerothread?id=1502084#) circuit low/high voltage
3...............P0107,P0108....................... .........Manifold Absolute Pressure (MAP) sensor circuit low/high voltage
4.............. P0335,P0336.................................Cranks haft position sensor
5.............. P1128,P1129.................................Map sensor circuit low/high voltage
6...............P0117,P0118....................... .........Electronic Coolant Temperature (ECT) sensor circuit low/high input
7...............P0122,P0123,P1121,P1122........... Throttle position sensor (TPS) circuit low/high input
8...............P1359,P1361,P1362................. ....CKP/TDC sensor 1
9...............P1381,P1382....................... .........CYP Sensor
10.............P0112,P0113........................ ........Intake Air Temperature (IAT) sensor circuit low/high input
12.............P1491,P1498........................ ........EGR valve
13.............P1106,P1107,P1108.................. ...Barometric pressure sensor
14.............P0505,P1519........................ .........IAC valve
17.............P0500.............................. ..............VSS fault
20.............P1297,P1298........................ .........Electric Load Detector (ELD)
21.............P1253.............................. ..............VTEC
22.............P1257,P1258,P1259.................. ....VTEC
23.............P0325.............................. ..............Knock sensor
41.............P0135,P1166,P1167.................. ....Primary heated O2 sensor
45.............P0171,P0172........................ .........System adaptive fuel too lean/rich
48.............P1162.............................. ..............Primary heated O2 sensor
58.............P1366,P1367........................ .........TDC sensor 2
61.............P0133,P1149,P1163,64,65............ Primary heated O2 sensor
63.............P0137,38,39........................ ...........Secondary heated O2 sensor
65.............P0141.............................. ...............Secondary heated O2 sensor
67.............P0420.............................. ...............Catalyst system efficiency below threshold
70.............P0715,20,25,30,40,53,58,63......... .Automatic transaxle malfunction
71.............P0300,P0301........................ ..........Random/Cylinder 1 misfire
72.............P0302.............................. ...............Cylinder 2 misfire
73.............P0303.............................. ...............Cylinder 3 misfire
74.............P0304.............................. ...............Cylinder 4 misfire
75.............P0305.............................. ...............Cylinder 5 misfire
76.............P0306.............................. ...............Cylinder 6 misfire
80.............P0401.............................. ...............EGR insufficient flow
86.............P0116.............................. ...............Electronic Coolant Temperature (ECT) sensor range/performance
90.............P1456,P1457........................ ..........EVAP control system leak
91.............P0452,P0453........................ ..........EVAP fuel tank pressure sensor low/high input


The following codes will not flash since they require a code scanner:
P1607-PCM internal circuit failure
P1705,06,38,39,53,68,73,91-Automatic transaxle failure
HOW TO CLEAR TROUBLE CODES (after you fix the problem)
a. Remove ignition key
b. Locate fuse panel on passenger's side
c. Remove fuse no. 13 10 seconds, and then place it back in.



your code is
45.............P0171,P0172........................ .........System adaptive fuel too lean/rich

you should note its to lean

po171 lean
po172 rich

http://www.automotiveforums.com/vbulletin/showthread.php?t=518731

complete list ...kinda what i just posted but more in depth to the obd II system as a whole

I know what the code means...I am asking what should be done to remedy the code...ie...replace O2 sensor or maybe fuel filter...if O2 sensor then which one---pre or post cat?

okay, let's start with some more trouble-shooting.

1. Does the car idle roughly? If so, does it idle roughly all the time, or just when the engine is cold?

2. Did your engine or exhaust get louder...even if only by a bit?

3. Have you done any exhaust work recently?

4. How many miles are on the car?


Basically, the car has too much air in teh air/fuel mixture. There could be a few causes.

Most likely a vacuum leak allowing unmetered air into the intake. Inspect all your vacuum hoses for cracks or coming loose. While idling, you can spray ether (whatever brand sold at autozone) over your vacuum hoses one at a time, if idle changes, you found your leak. Make sure to check the rubber pcv hose (usually elbow shaped) behind the throttle body...it's a common leak because of hte angle.

An exhaust leak maybe the cause inaccurate readings/discrepancies between the 2 o2 sensors. So if your exhaust/engine got louder, I'd start there. Lie ont eh ground and look under the car on a cool morning and see if you can see exhaust coming out from anywhere other than the muffler, if so, get that leak fixed. It may be a crack which can be welded, a worn flex section that can be replaced, or simply a leaking gasket.

It could be your air meter in the MAF. I don't know 99s specifically, but it will be the part between your intake filter, and your throttle body that has wires running to it. Many times this can get dirty if you have an K&N filter and over-oil it. You can take it all apart and used some q-tips sprayed with carb cleaner to clean the gunk buildup off the sensor. Careful! it is very FRAGILE Reassemble it. I will admit, sometimes cleaning these isn't enough. Sometimes they are too far gone or damaged. It happens, if you get to the point where you cannot find any intake or exhaust leaks at all, even including the intake and exhaust manifolds, and cleaning the MAF sensor doesn't do the trick. Try going to a junkyard or www.car-part.com and finding a used MAF to switch in and see if it fixes the problem. It's cheaper than spending $300-$400 for a new one at the dealership.

I wouldn't even bother with the o2 sensors, they would throw other codes if they needed to be replaced.
If somebody at your local autoparts store or dealership says to replace them, don't listen. Same with the fuel filter, I really don't see that being the cause.

Let us know how it goes or if you need further help.

Thanks for the response Igo...In response to your questions...the car doesn't idle roughly at all...there has been nothing done to the exhaust recently...and the car has about 104k miles on it. I will check the exhaust for leaks as well as vacuum leaks. I should also note that the light just went off by itself, so hopefully it was just a fluke or some carbon deposits on the O2. I'm not sure but I will keep an eye on it. Thanks for your response it was much appreciated...