[Steve Cole]

The saga continues: So I cleared the codes two days ago and went for a drive. My check engine light came back on very quickly and I assumed it was the same codes but no, instead of the O2 sensors I now have PO171 and PO174 (fuel trim system lean bank 1 and bank 2).

Possible causes:

HO2S element is contaminated, deteriorated, or has failed.
Vacuum hose is disconnected, broken, leaking, or loose.
One or more injectors restricted or pressure regulator has failed.
Low fuel pressure (fuel filter clogged, pressure regulator failure)
Fuel control sensor is out of calibration (ECT, IAT, or MAF)
Air leaks in intake manifold, exhaust pipes, or exhaust manifold.

I am certain the my O2 sensor faults are probably coming back the next time I drive it so I suspect these new fault codes are somehow related.

Let me address some of the possible causes-

O2 sensors were originally brand new AC Delco units but I recently replaced with the two that came off the donor truck (for troubleshooting)
Vacuum hoses all look good. The vacuum hose that connects to the brake booster was a little loose though so I tightened yesterday.
I had my injectors cleaned and flow checked not too long ago
Fuel filter and pressure regulator are new (less than 100 miles on everything)
Fuel control sensor out of calibration- Could be, I don’t know
Air leak in intake/exhaust manifolds or exhaust pipes- I checked the intake and exhaust manifolds yesterday, all is torqued. I checked the exhaust pipes from the headers to half way back yesterday. So far, the clamps are tight and welds complete. Will do the back half today.

All these faults have to be related somehow; I am looking for suggestions to troubleshoot this.

Anyone??