How to access injectors

I have a 2006 Cadillac STS with the 3.6L v6 engine. Originally had P0420 codes which resolved with new O2 sensors and new catalytic converter on passenger side (Bank 1). Then started throwing P2178 codes. Scan showed LTFT at -30 on Bank 1 and just slightly elevated at -7 on Bank 2. Rich condition is probably what caused the Catalytic converter to go bad in the first place.
All new spark plugs and all new fuel injectors. MAF was cleaned and tests good (doubtful that was a problem because high negative is only showing up on one bank). Accessing the COP primary ignition with a scope, but cannot get any kind of decent secondary ignition signal, using Hantek 1008c scope and OTC Tools 3825-56 Universal Scope COP Probe. Intermittent signal did show a problem with cylinder #1 and we fixed the connection. Other primary ignition waveforms were good. I am new to using the scope and still having problems with learning how to capture and save so I cannot post pictures.
The problem is that the intake manifold on this car is so large that it sits on top of the injectors and also sits on top of almost all of the coils. Cannot even change coils or plugs without pulling the intake manifold. Backprobing the coil on plugs can get me the primary ignition waveforms, but I cannot figure out how to backprobe and get a waveform on the injectors. I want to see if the "bump" shows up indicating that each of them is actually opening and closing, since I suspect one of them is not and is causing the rich condition.
I see no way to backprobe the connector at the ECM. Was hoping someone here had an idea of how to do this. The car cannot run without the manifold installed. Do they make a breakout box for the ECM? How else could you test them?
I bought the "ScannerDanner Book" and am frustrated that the first car I tried to use this information on is this difficult to access.

At the passenger front corner of the intake is a bulk connector that goes under the intake. Pretty sure it's called C115 on the OE wiring diagrams. Best place to test your injectors without intake removal, besides the PCM itself. Just like the coil connectors, pull up on the red part to separate it.

If you get a chance, have a look at your upstream A/F sensors and the downstream O2's at idle? That'd be the easiest way to confirm a single bank issue, and allows us to possibly rule out a skewed wideband sensor. While you're there, does the Misfire data show any potential suspects?

And yeah, you'll never have any luck getting a secondary pattern on these. :lol: Far too much shielding at work. Even my Pico TA204 probe won't produce jack or squat.

What I can help you with is saving Hantek screens as the Hantek menu save image file just dosen't work, the software is full of bugs Hantek never seems to fix BUT it isn't a problem here are links to two methods to capture Windows screens.
httpHowtogeek how-to-take-screenshots-in-windows-10

But my method of choice is a shareware program called Greenshot Greenshot home page it will save screen shot images to file or open them in your image editor of choice --- I use the old style MS Paint.

Thank you. I love the screenshot saving to a file. Did not know that was available in Windows 10. That is a super feature. Thanks!

I'll look for that connector tonight. Was looking at schematic and thought injector signal wires ran straight to the ECM, but did not look that close.
I did get some secondary ignition waveforms, but it was real finicky. Had to run the induction probe up and down and all around and if you got it just right, the signal would come through. With everything going to COP you would think there was a better tool out there.
Thanks for the help!

No problem! Let us know what you find with the injectors. I usually only see injectors stick open on the GDI versions and not on the port injected ones, but I see new stuff all the time. :silly: