Late last week I started getting the P0174 (System too lean bank 2)code pop up on the DIC and the car seems to go into "limp mode". If I clear the code it will run ok, but not great and then as soon as the light comes on it will start running pig rich.

After some research I found this issue is commonly from an air leak after the MAF or an Exhaust leak before the 1st set of O2's. The air coupler was pretty mangled and there were some spots that could have been leaking around the bottom of the rim. I'm pretty sure that I was able to stuff it back on the throttle body so it won't leak (I ordered a new one just to be safe). I also replaced the fuel filter because it probably needed to be done anyway. I also cleaned the MAF sensor while I hade the intake apart.

The previous owner installed a catch can so I believe that replaces the PCV valve . . . someone please correct me if I'm wrong.

My main concern is that I am only getting P0174, not P0171 (system too lean bank 1) for the other side. If I had some sort of leak wouldn't it show lean on both sides. From what I've read on here it's probably not the O2 sensor itself as those codes usually look like "O2 sensor malfunction/low voltage/high voltage ect". Does anyone have any other things that I could check into. I really do not want to take the shotgun approach ($$$$) and replace everything from the O2 sensors to the fuel injectors.

Thanks in advance

 

ttt

 

Is the air intake OEM or aftermarket?

Ranger

 

It's a vararam intake that was installed a few years ago.

 

Many aftermarket cold-air intakes create turbulence around the MAF sensor that has the effect of falsely provoking the setting of P0171 and/or P0174. That usually occurs as slight throttle-openings such as off-throttle down a hill approaching a stoplight. It does not occur under wide-open throttle where it would be of concern.

I learned this driving 01 and 02 Z06s with a sometimes mounted CAI. I'd get intermittent P0171 or P0174, rarely both. and always under mild city driving, never during the 500 passes the cars had at the drag strip. Neither car ever had an engine issue and the 02 is still trouble-free with its third owner probably still setting an intermittent false code when the CAI is mounted.

But as an owner, I'd do the following:

(1) check and retighten all clamps on the air intake. Ensure no air leak.
(2) If the CEL recurs, pull the codes and write down the flags. Ensure none are C (means current). If it is alway flagged with an H (means history), then it really reflects a transitory condition that I wouldn't sweat.

Ranger

 

Thanks Ranger!

On the way home tonight I also got the P0155 code. I am going to instal the new Air Coupler and new Vararam filter while checking all the clamps and hoses and hope that it will take care of it. Thanks again.

 

OK. So I replaced the air coupler (Had a small tear at the throttle body end) and that got rid of the P0174 code.

Now I am getting the P0155 code (02 Sensor Heater Circuit Malfunction Bank 2 Sensor 1). I also occasionally show a P0154 (P0154 02 Sensor Circuit No Activity Detected Bank 2 Sensor 1).

Normally I would say that I am in need of a new Passenger Side front O2 sensor, but I can't help but wonder if this has something to do with the lean issues I was having earlier. Any advise before I drop $70 on a new O2 sensor?

BTW, this car has longtubes that were installed years ago. The vararam intake has a slight leak where the bridge connects (A new one will be here Thursday). All this has been going on with the same tank of gas, which also has Fuel Injector Cleaner in it.

 

^^^ I would suggest
(1) installing the new air bridge
(2) then, rechecking tightness of all the air path connections
(3) clearing the codes
(4) put 50 miles on the car, during which you check for codes periodically.

After doing that, you should learn whether or not the 02 sensor codes are transitory.

Ranger