05 H2. Truck sat for 7 years. We just pulled the body off, blasted and painted the frame, and put everything back together. Runs, but missing on 4 of the 8 cylinders. Each cylinder has spark. Tested for voltage at a few of the injector plugs, only gets 6v. If I grab ground from the chassis, it gets full 12v. Truck has other weird electrical issues, mainly gauges and HVAC. Has code U1301 among others. I think its a ground somewhere. Possibly ECM. Where exactly does the ECM get its ground, and what pin on the ECM can I check for ground? Where do the injectors get their ground from, ECM?

Thanks!

 

So I figured out that pins 0 and 40 are PCM ground, and I do have ground there on the connector.

I pulled a PCM out of an 03 Avalanche and installed it. Re-learned the passkey. Fuel pump wont kick on, but I was able to spray starting fluid and it seem to have ran like it should. I think the issue is the PCM, so I ordered a refurb from ebay.

 

Have an 05 too.

Yours must have had quite a lot of work, never seen a chassis before.

Does ECM mean PCM?

Code U1301 relates to the Class2 Serial Data, many modules connected to this bus, so the weird issues could be a missing ground on one of the modules (PCM?)

The PCM doesn't have a pin 0 (I don't think), could it be Pin 1? PCM-Pin1 is ground connections and also Pins 24, Pin 27, Pin 40, Pin 64, Pin 67

From the diagram, the injectors have one pin "HOT" all the time via the two fuses INJ1, INJ2 (both 15A) If one of these is gone you'd loose a set of 4
FUSE INJ1 = Injectors 7, 5, 3, 1
" INJ2 = " 8, 6, 4, 2 Plus Circuits 26 + 27 (?,?)

The Fuel Pump Relay is controlled by PCM-Pin9 and HOT via Fuse PCMB (20A) Under The Hood

Please keep us posted... good luck!

 

Yes, PCM/ECM same thing. We did do a lot of work. Sand blasted and painted the frame. Replaced brake lines and hoses, fuel lines, fuel pump, body mounts, exhaust manifolds, among other things.

I did mean pin 1 and 40. Those are PCM ground, which is where the injectors get their ground. Random cylinders arent working, not a whole set. Engine ran like it should when we swapped the PCM. So I'm pretty confident the PCM is bad.

Also, it sat for 7 years, and unknowingly had a leak on the top drivers side cab marker light, and I think it leaked onto the BCM, causing some interior electronic issues. Any tips on removal?

 

 

Just saw your pics, very impressive

The BCM is tricky as I understand, best not to go there unless you need to. However, I did find this link to a post on this forum which might help.

Any particular electronic issues?

I take it code U1301 has gone away?

Note all pins 1,24,27,40,64,67 must connect to ground, according to the diagram. I sorted out these references from the manual, look at P5 in the attached PDF

You must now know plenty about Hummer H2's