Contour Enthusiasts Group Archives Forums General Troubleshooting BANK 2 LEAN

i have a code P0174 (means bank 2 lean). my question is (by the way i have a 99 SVT) bank 2 is the down stream? or is there a O2 on each manifold? i ordered a mil eliminator because i thought bank 2 would be the down stream which wouldnt matter performance wise. but is that right? i figured why spend $ on an O2 when i can basically mimick it w/o performance loss. the only engine mods to the car is resonator delete, and fabbed K+N intake. it shouldnt be lean right? any help would be great. PS put a Fidanza flywheel in the other day and the car only went .04 tenths faster in the 1/4, and picked up no mph. what up? weather was about the same as was car temp. and 60ft.

so i guess what im asking is how many o2 sensors does a 99 svt have and where are they located. also which one is bank 2?

WHOA!!!!
Did you just suggest that he install mil eliminators on an upstream location?

original post, remember this: a "lean" code could mean just that.. you really could be lean.

Leaking exhaust manifolds at or near the sensors, leaking gaskets, etc..


Ray

Ok, so how do I check which o2 is bad? The upstream or the downstream. I guess I could just install the mil on the downstream and see if the light comes back on. Also when I reset the computer it takes about 80 miles or so before the light will come back on.??????

Let's start over on the explanation of your oxygen sensors.

You have four sensors. Only two of them are used for determining fuel mixture. Those would be the upstream sensors. The downstream sensors are used to determing the health of the cats.

Bank two happens to be the front bank, the bank closest to the radiator.

So you are looking for the first oxygen sensor on the front bank. It would be just in front of the cat that is built into the exhaust manifold.

MIL eliminators are only used on the downstream sensors. The downstream sensors are mounted just behind the cats in the exhaust manifold. On our cars, the downstream sensors do not monitor the main cat which is a little further back after the two pipes join into one.

MIL eliminators are needed if the cats in the exhaust manifold are disabled (gutted) or removed (headers installed instead the the stock manifolds).

The upstream sensors give an instant voltage signal to the computor telling how rich or lean the system is. The sensor generates voltage in the absense of oxygen. The range is .1 volts (lean) to .9 volts (rich). The voltage is constantly switching throughout the range because the exhaust pulse contains different mixtures depending on the part of the combustion cycle the cylinder is in.

The downstream sensor with a healthy cat will move much more slowly since the cat evens out the mixture (or buffers the mixture). If the downstream sensor switches at about the same rate as the upstream sensor, the computor knows that the cat is not healthy (or missing). The portion of the computer that checks the downstream sensor reading (cat monitor) does not run all the time. It only checks the cats after certain driving conditions have been met.

With all of that said, most important of all, is that an oxygen sensor code may not mean that the oxygen sensor is bad (in fact, most of the time oxygen sensor codes are from something other than bad oxygen sensors). The codes are not the final answer, they are only the gateway for testing and indicate the general area that needs to be tested. You may have a vacuum leak or dirty injectors for example.

Thanks Big Jim I can tell your edumicated. Since the light comes on after about 80 miles or so after reseting does that mean ?? what? The car is running lean once in a while? I pulled the plugs and they look great. Maybe Ill have my injectors cleaned, and change the fuel filter.
ps- "leaners meaner"

The 80 mile reset time is simply because your car only runs the cat monitor (in Jim's description) once a certain set of driving conditions are met; above 65mph for more than 10 minutes, with the AC off, for example. (that is NOT the routine, but I was just giving examples)

It just takes YOU about 80 miles before you do whatever it needs to trigger the cat monitor.


Ray

The cat monitor has nothing to do with code P0174.

It sounds like you need to read the oxygen sensor in real time with a scanner during a road test.

Ok im not to hip on OBDII. When I hooked up the scanner I saw the O2 voltage jumping around on all O2s. So by doing a road test would anything change from sitting in the parking lot reving it(steadily)? Also just to try and rule out a bad sensor- if the O2 were bad the light would come on right away, yes? Since it takes awhile to come back on after reset this means the car is actually running lean? PO174 code= which O2- upstream? yes? Thanks for all of your input so far guys.