Tmarks91

Ive had a few different check engine lights for the past 3-4 months, p0154, p1174, and p2a03.. Does anyone have any reccomendations on what to do about these? I have PCD's and a Jpipe for my mod's im pretty sure these are related to the problem but i am not 100%. Also my gas hasnt been holding up quite as well

Opel

P0154 is the heater system malfunction on the LAF sensor..that's the front top sensor on your cat.
Have you tried resetting? Sometimes, a simple reset takes care of a CEL code caused by a temporary electrical glitch/fluctuation.

The other way is, replacing the front LAF sensor with the rear sensor, and see if you get a different code (for the rear). If that's the case, you know the sensor is bad.

The other 2 codes I'm sure are associated with this code. Obviously the LAF sensor isn't working correctly, which then screws up the AFR, causing an imbalance, and also an out of range reading by the O2 sensor after the cat (lower sensor)

Tmarks91

Gotcha, and no have not reset my car yet...Btw my gas mileage has just been hoooorrible, do any of these problems have to do with burning more gas? Do you think any of these codes r severe problems?

nfnsquared

All of those codes point to a bad A/F sensor, or a bad connection at the sensor or the ECM/PCM.

Since the sensor was touched (I assume) to install the PCDs, check the connections at the sensor. They could be loose or the sensor could have been damaged.

And yes, a faulty A/F sensor or bad connection to the sensor could affect gas mileage.