Lean Code

[jabo731]

It all started abut 2 months ago, chec engine light came on and the wrench said I had a lean code. We cleaned the throttle body, change the fuel filter and replace the pcv valve. 3 week later it came on again. I didn't bother going back to the Dealer because the service manager is a dick.(he doesn't like my car because its not stock). Took it to a friend of mine whos a wrench, he tighten the PHP intake spacer and reset the code. 3 days ago check engine light on again says Lean on BANK 2. I don't know if it always said bank 2 because the wrenches never said. Today I made a point to read it myself. So what could it be Lean Bank2 and how can I correct it.....

[merc]

Basically this means that an oxygen sensor in bank 2 detected a lean condition, too much oxygen in the exhaust.

Check for a dirty fuel filter and proper fuel pressure.
A stuck or leaking EGR Valve
What type of aftermarket goodies do you have ?

[jabo731]

Kooks full system minus the cats(02 eliminators) flowmaster 40s Megs 4". I have an intake spacer but my motor is stock.

[merc]

Kooks full system minus the cats(02 eliminators) flowmaster 40s Megs 4". I have an intake spacer but my motor is stock.

How long have you had the kooks system. I am thinking it may be the EGR. Oh, how many mile are on your car currently ?

[DEFYANT]

Could the O2 sensor be wrong? Try swapping with the one on the other side and see.

[jabo731]

I've had my Kooks for about 35,000 miles. My car has 40,000 on it now. Charlie I don't think I have o2 sensor because of the eliminator plugs correct?

[DEFYANT]

I've had my Kooks for about 35,000 miles. My car has 40,000 on it now. Charlie I don't think I have o2 sensor because of the eliminator plugs correct?

D'uh!

That would make sense!

It must be reading something to trip the code though.

[Breadfan]

I don't think you removed the O2 sensors, you still use them, you just probably have MIL eliminators on them to keep the check engine light from being on using an off-road xpipe.

The mil eliminators are wired in after the O2 sensor: http://www.mileliminators.com/

[jabo731]

Breadfan thank for that info. I was under the impression that the O2s were removed. So this means that I can have a bad O2 sensor.

[greggash]

I had the same type of problem;

I ended up replacing the O2 sensor on the drivers side.

But you are correct to look for a vaccuum leak at the intake, even at the exhaust flange.

You have 4 o'2 sensors, the rear two are off or have MIL eliminators.

You'll find it

[jabo731]

How can I test the O2 sensors or rather how can I tell if one is bad? How much do they cost? would it just be easier to replace both?

[JMan]

Greggash is correct, you have four and if two are turned off, it's the rear (after catalyst) that are turned off. Your "wrench" needs to check for pending codes to see if the other bank is askew as well. It may have not quite set the code yet. Those codes (P0171 lean limit reached bank1 and P0174 lean limit reached bank2) are generated when the Long Term fuel trim has gone as far as adding 20% to the fuel mix for over twenty seconds. This is indicative of a lean condition (obviously).

If both banks are adding fuel like crazy, the problem is centralized like a central vacuum leak, poorly sealing EGR valve or faulty sensor. In this case the MAF sensor is most suspect especially if you have an oiled air filter. It would typically show up as a very low BARO (barometric pressure) reading. At sea level the BARO should read 159hz +/-3hz. Once again, that's at sea level! I have no clue what it is in the highlands (Dumb cracker-boy alert!). Over oiling will foul (soil) an MAF every time.

If it is just one bank, you may have a vacuum leak specific to one side or an exhaust leak which is drawing oxygen rich air into the the pipes ahead of the oxygen sensor. You could also have a faulty oxygen sensor. That would be easy for the tech to see by comparing it to the other side!

Most importantly, the conditions when your check-engine light comes on are the ones you need to recreate when checking (testing) the system. In other words, if the light came on during a steady drive @ 55mph, then that's the speed and load in which it needs to be checked. Testing at idle won't necessarily show anything!

Best luck,

J

Dude, Brooklyn is the same elevation as where I'm at! 159hz +/- 3hz on the scan tool!

[thePunisher]

a leaking egr will not cause a lean condition....the egr recirculates spent gasses...of which there is very little oxygen......not enough to cause a lean condition...

the downstream 02 sensors will also not cause this. they are simply catalyst monitors and do not affect a/f in any way. they simply tell the pcm if the cats are doing their job.

if youre getting bank 1 and 2 lean codes id go to the maf sensor. see if the tech can give you a baro reading using a scan tool. iot should read in the mid 150s hz depending how close you are to sea level. a bad maf will give you a lean condition. also check for air leaks aft the maf in the intake tube.

[thePunisher]

sorry i did not read the post about the baro above...sorry for the double info

[superford3]

first thing is first what are your fuel trim readings on the scanner and second look at what the oxygen sensors are doing,start there and answer back

[John F. Russo]

I had a persistent periodic lean code. Eventually it was found to be a valve problem with cylinder #8.

It was confirmed when they checked the compression and found it to be about 20% too low.

[Paul T. Casey]

If you're running a K&N or other "oiled" type of air filter, could be as simple as buying a can of MAF cleaner (NAPA). I get one from time to time, cleaning seems to do the trick.