GMC Suburban P0174, P0154, p0151, p1153

First off thanks to whomever answers this and tries to help out.

1997 GMC Suburban 5.7L Unleaded Engine; R Vin. 213K miles (I drive 40K miles a year on this vehicle)

The work that has been done related to the problem (some of it before the problem surfaced):
Intake Manifold Gasket, 60K miles ago
Two new Cats, direct bolt on, 5K miles ago
All new vacuum hoses, including PCV valve, hose, elbow, and gromit.
Tune up with AC Delco Plugs, Rotor, Cap. Magnecor wires.
Fuel Filter Replaced at regular intervals.
Fuel Pump replaced 30K miles ago.
Mass Airflow Meter 3K miles ago.

The history:
One year ago I got a MIL checked the code it was po154 I figured the the O2 sensor was bad replaced it. It appeared that the problem was solved.

Four weeks later the MIL came on again, same code. Replaced sensor (figuring I did not tighten the first sensor on to the right spec), problem solved for 10 months.

Get same code (or p0151, p1153 all O2 sensor codes) again this time with a p0174. I replace the O2 sensor and all codes clear. Since this time I have replaced the O2 ever three to four weeks. Normally the O2 sensor code appears before the p0174, the last two bad O2 sensors this has not been the case the p0174 appears and then the O2 sensor code.

I did a dummy check to see if the Intake manifold gasket was leaking by plugging the openings the valve cover for the breather hose and the pcv hose and checking for vacuum on the dipstick tube, I felt none.

The exhaust stinks while driving in the car a running around town or on the highway. And Autozone and Kragen are beginning to wise to my constant replacement of their O2 sensors under warranty. The car will be going to a shop I am just trying to delay going and to see if I am missing anything.

Check for vacuum leak(s) at the intake gaskets on Bank 2.

Check EGR.

Check wiring and connections for proper voltage(s) and grounds from the pre-cat O2 Sensor on Bank 2 to the PCM.

Are you using quality parts?

Sounds like a wiring/circuit problem along with the lean condition.

Good luck and keep us posted.

How would you recommend checking for the intake gasket leak on bank two other than what I have done? Spray with starter spray?

I will check for a wiring problem and the EGR in the next few days. Any recommendations on checking the voltages and grounds between the PCM and O2 sensor? I do not think I have all of the specs for this in my Chiltons.

All parts have been dealer other than the O2 (Bosch OEM wiring) and the spark plug wires (Magnecor)

Thanks for the reply.

Joel

It sometimes is more obvious with a scanner and watch the fuel trims, it may be leaking enough cold to change the fuel trims but not affect the idle speed in the traditional way that vaccum leak testing would!