SJC...Had you typed the code in correctly back when...I'd have found it on my search.

P0171 Lean Bank 1 aka front sensor is telling the PCM to adjust the fuel ratio outside of it'* "normal" range.

Pull your negative cable off the battery and look under black boot...any corrosion?

So far..I have done
Cleaned battery cable at both ends....and I mean..dremel tool wire brush..then contact cleaner clean.
Also cleaned the ground on the back of the engine next to the oil pressure sensor.
Pulled the wiring conduit off and ensured a good connection at S110 (that'* a splice 4 inches away from the alternator)
Replaced loud fuel pump, strainer and filter
Swapped injectors out with a perfect flow matched set
Swapped Maf
Checked IAC
Checked TPS
Replace vacuum hoses...every single one
Pulled regulator and checked it.
Sprayed engine looking for vacuum leaks
Cleaned bottom of ICM/mounting plate
Cleaned every single ground, body and engine within the engine bay.

All of this started right after I changed the battery and noticed some corrosion on my negative battery cable. My new cable is on order from GMPD and I can't wait for it to arrive...Then I will put it on..clear the code..and watch it come right back on. Pound my fists a little and look for something else.

In other words..yeah..I'm working on this issue for you.

I have had the codes pulled several times, the last time before I changed the o2 sensor it did have codes for low voltage and high voltage to the sensor aswell as the lean bank 1.I'll get it scanned on my way home this eve. The only other code that it ever gave me was for taking too long to warm up it hasn't been back since I changed the stat(195* for now).

Boost: I thank you for working so hard on my issue and sorry for having bad short term mem.

Lash the title will be different in just a second. and nope nobody with a pressure tester.(how much just may buy one?)

Thanks so much I REALLY appreciate it.

Ok just got it scanned a little bit ago,only code was p0171 lean on bank1.
One thing i've been wondering is could this be a contact issue at the sensor bung?I have been thinking about possibly borrowing a tap from work and chasing the threads just to ensure good contact. I havent because if I screw up I dont want to have to drop the down pipe to weld in a new bung. just a thought.

Welcome back to the lean bank club brother

Don't chase the threads. Sensor is probably grounded via wire as well as through the bung.

Look at the battery cable..any corrosion? Also climb under and remove the ground to block on the front of the engine (if that'* where 00+ still is) clean it up..reinstall. If it'* the same as 92-99 it'll be a 13mm bolt on the front of the block behind the AC compressor.

To give you a little more background on our favorite code.
To set the SES light, the lean bank issue must exist two consecutive run cycles. To automatically turn the light off..there must be 3 consecutive run cycles w/o the issue.

Do the easy free cleaning stuff. Don't bother going after Splice 110...it'* very doubtful that it is the problem.

I was thinking more about this and was curious if when they fixed My LIM gaskets if it would be possible they didn't get a good enough seal on the SC gasket. I'm assuming there would be no way to check this other than removing the SC and changing the gasket and the o-rings. also when I was looking around the mani they used glue on the gasket is this a common practice. I am under the impession that on most gaskets you dont use glue.

probably shooting blanks in the dark but this did all start after an LIM repair

thanks again

It is common to use some RTV or other sealant at the corners where the gaskets meet. Take a look in some of the threads that have pictures of the assembly and you'll see that.

Being that we have basically the identical issue and engines. I doubt it. I swapped my gaskets myself and had too much time w/o the code. Have you looked at the battery cables for corrosion under the rubber booties?

RTV used on corners of gaskets
First under rubber

Then over as well

Last picture before LIM is put in place

Thanks but I know quite well about the rtv glue on the corner of the gasket / valley. I should have clarrified better, they glued the gasket between the SC and the manifold. They spilled a little glue on the outside of the manifold below the SC. It looked clear but is now turning brown from the heat.

I checked the battery well what I found was a clean terminal and the battery appears to be new( going to have it tested soon). (remember my battery is under my back seat)The thing that has me woried is the vent hose from the pos sie of battery had obvious signs of corrosion inside and a small crack in the bottom. when I moved the battery I found traces of a previous battery with a corosion problem.

gotta run late for work

Battery acid is bad...I'd clean it up as well as possible.

Ok.. you said the connection was good, do your little boots at the ends of the cables come off? That'* where I found corrosion...under the boot.

How about checking the connection to the engine block, with your cable traveling that distance..there'* possibilities. I wouldn't condem or rule anything out at this point.

You could clean the grounds again, check splice 110 in the engine harness and double check the O2 sensor connection again.

Having the FSM and reading up on this code a lot, I've found this...it'* the great unknown code. They say to check pcm connections, all grounds, other sensors, the O2... darn near everything. Which then narrows the problem down to anything. My light went off again this morning. it'* becoming more intermittant and flakey as the weather warms up.

My only hopes are that another code sets and it'* the root behind P0171.

Check the power lead connections to the under seat fuse block, and under the hood. I recall someone posting that they had problems with one of those being loose. However, I don't recall which one, nor what the symptoms were. (Old-timer'* disease).