2003 H2 with 83k miles
The other day I drove my H2 to work and put about 100 miles on it before I got there, no issues. When i went to leave work I want to say I immediately noticed it seemed weaker on crank, shortly after the Check engine light came on and it was struggling and even died at a stop sign. Decided to chance it on the interstate and made it 45 miles home but while on the interstate it still felt off under acceleration and the tach was basically bouncing off 0 unless i was accelerating but the rest of the gauges seemed fine. Check engine light reported MAF sensor, checked it cleared the codes and thought it might have been the intake tubing because after i reconnected it truck began running normally again. Since then Ive taken it on a few shorter drives and runs perfectly.
Yesterday I moved the truck into my yard and left it overnight, today its back to running poorly again, weak, gas almost sounds like you are flooding it and the check engine light started blinking but didnt set off the light. Kind of at a loss of where to begin or check first.

Few other issues
Air suspension relay randomly clicks near the compressor but only when a door is open, when it shouldnt even be operating. It sounds like it shorted and also doesnt always do it.
Keyfob unlock, cant unlock the truck consistently , sometimes it works on first press other times it takes 20 or so presses before it unlocks, lock always works , multiple fobs do same thing and replaced the passenger window switches/ keyless module but still same issue.

I was leaning towards BCM until the recent dying issues, now im not to sure but wouldnt be surprised if they are all related. Truck is a AL/GA truck so its surprisingly clean underneath and no real rust plus ive check alot of the grounds but none of them looked remotely bad. Also both times is when it sat for awhile not connected to a battery maintainer but didnt act like the battery was weak.

thanks in advance for any advice

 

Since disturbing the air intake tube fixed it for a while, I would double check that. If that's the original mass air flow sensor, I'd probably just go ahead and replace it.

One of the first things I look for on an H2 with random electrical issues besides the grounds.... Pop the door sill plate off on the driver side. Just price straight up on it and it will snap out. See if it's an inch deep in water, which will mean part of your harnesses submerged. That's actually pretty common from a leak at the front driver side marker light, or water leaking around the little bolt under the lens that holds the rack down to the body.

On the grounds, they may look good.... But you really have to remove them, clean the ring terminals and the mating surface down to bare metal and reattach. Pay special attention to the one on the driver side of the engine block just above the oil pan lip. As well as the one from the back of the cylinder head on the driver side up to the firewall, and the one at the very front of the driver side frame rail, accessed through the opening by the tow hook. I think those are three of the most crucial ground points. The ground point behind the driver side rear tire is crucial for your fuel pump as well as a few other items. If you discover water under that sill plate, pull the piece of plastic that surrounds your parking brake straight back and it will unsnap and reveal another ground..... If any water intrusion, that one tends to become an issue. The other ones under the vehicle attached to the bracket for the body mounts tend to be problematic as they're exposed to the elements and are definitely worth cleaning. I save the ones at the base of the b pillar on the interior for last, simply because they take longer to get to and I've never found one yet that was corroded. If you're positive and negative cables are still the original, they definitely need replacing by now.

 

And by the way, the blinking check engine light usually indicates a misfire. As mentioned above, I would ensure everything is grounded well and no leaks in the intake. New mass air flow sensor. If you replace the intake manifold gasket, might as well do a new GM or ACDelco oil pressure sensor while you have it off. Running it too long misfiring will kill your catalytic converters....

 

The tach issue is a symptom generating from either the crank or cam sensor, the ECM gets the tach signal from one of them and displays that reading on the instrument panel.
A bad reading from either of those sensors will cause the conditions your truck is having (flashing engine light and running bad)
I would start with the connectors on both sensors, pull and clean the metal contacts then check and see if the tach works correctly and the truck runs as it should.

Neal

 

Well it looks like I have a list to go thru and check, thanks. FWIW i went outside after the post and everything was running normally again. Only thing I did was let it sit on a charger and time. The battery did nearly die before the running issues began and it ran down rather quickly when I was running a scanner on it but running voltage is good. I do not think I have any water/leaks but will double check. Whatever it is is defiantly intermittent.

Ill give it a go and report back tonight , thanks all

 

Definitely get that battery load tested before proceeding. A bad battery triggers all sorts of bad things.

 

Yeah Like wiping out your $2000.00 NAV Radio if the guy changing the Battery F's up. Ask Me how I know? ​​​​​​​

 

Your 2003 still has a replaceable fuel filter, I would add an AC Delco or Wix fuel filter to the above list.

 

a 2003 also has an external pressure regulator on the drivers side of the intake plenum that has vaccume hoses.

 

That's right, and it's a fun one to change. Right in front of the fuel tank, you can get one hand over the front of the cross member and try to disconnect the quick connect fitting. If I remember right, I was able to squeeze my left hand between the tank, and crossmember from behind to hold the filter itself. Then about a cup of fuel comes down on you :-) Mine look like the original, or at least 15 years old, which is probably a why it put up such a good fight.
So, it should go without saying, but..... You don't want to be smoking when this happens.

If you're quick connect fitting cracks, most auto parts stores have the fitting as well as the plastic tubing in stock. Pretty easy to work with when the stuff is new.