OK, maybe some of you local guys that know a thing or two about tuning since no one else is responding:

A little background first: I recently changed my clutch, and in the process I had to remove the headers. I replaced the drivers side 02 sensor because a bare wire was showing from rubbing on the frame. The pass. side O2 sensor looked fine and had no issues. I'm also not running cats but still have the rest of the emission hooked up (AIR pump).

So now I'm finished with that and I'm driving the car. I keep setting a P0154 DTC. Besides the check engine light, the fuel mileage is down about 25%. Also, I can hear what sounds like the AIR pump running constantly. The light will come on about 5-10 minutes after I've been driving. If I clear it, it will come back on the next time I drive the car.

I don't know if the AIR pump running constantly is causing the P0154 or if the code is causing the AIR pump to run.

I did some monitoring with HPtuner last night:

So bank 2 02 sensor is pretty much constant at around 450mV, which according to the manual would be a problem..."inactivity" or something to that effect.

However, Bank 1 is cycling between 0 and ~500mV (don't remember for sure...but diffenatly down to 0) Also, the Bank 1 LTFT is maxed out at 25 (If I turn it to closed loop) if I reset the LTFT and turn on closed loop it quickly goes back to 25. It also starts missing and running poorly in closed loop. The bank 1 injectors also begin to increase in duty cycle.

So I'm thinking my gas mileage is down because its not going into closed loop mode and because the computer is adding a bunch of fuel.

I checked the wires connected to the 02 sensors and all looked well.

I was just reading on HPtuner forum about a 02 sensore heater fuse, I haven't gotten a chance to check that, but where is it at? Under the hood?

Anyone got some more ideas or more checks to do?

 

try replacing old sensor if before the swap things were fine. from there Iduno quite the head scratcher. ~Guy

 

Well I think I've found the source of the problem. The new o2 sensor was rubbing on the frame just like the old one (even though it was smaller) and I'm assuming it was grounding out the circuit, causing the o2 fuse to blow.

So I removed the header and I'm working on putting in a new O2 sensor bung. Hope that solves it.

 

sounds like a great place to start anyway. let us know how it works out ~Guy

 

That's what it was. The new o2 sensor wires were grounding themselves out on the frame blowing the fuse.

I got a new bung and welded it in. Now the o2 sensor doesn't hit and its working right. To bad I wasted the $55 on the other one...oh well, lesson learned.