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Not totally up to par on Hummers but given today's environment of development in electronics, ECM's, BCM's, PCM's, modules and such, I would suggest a dialog with a Hummer mechanic or at least a GM mechanic at your local GMC dealership. Sometimes they, or that of the service manager, haven't a problem with people asking such questions. Other than that, if Hummers hold true to older GMC models, most of the exterior lighting is pumped through the mutifuntion turn signal switch.
Disconnect the battery post connectors and use a pick and needle-nose pliers. If the fuse holder is melted, I'd recommend cutting out the melted fuse holder and installing a new one of properly gauge rated fuse capacity.
Another possibility is that you could have what's called a loose baffle inside the fuel tank which is supposed to be ridgedly mounted inside the tank but has become loose and moving around which could block the flow of fuel entering the tank. Also take a look and see if there's a rubber hose which connects the fuel fill to the tank and see if it has become collapsed. I've see this in other vehicles where the purge/vent solenoids (associated with the canister) failed causing this problem.
5.7L. engine...anything involving the ignition system, spark plugs, spark plug wires, etc. is best to leave to a professional. It gets pretty involved and use of specialized tools are required.
You would need one heck of a better description than this including mileage and how is the performance of the vehicle. Better to let a professional make this diagnosis, in front of the car.
My guess, the reason you replaced the pump is due to pump whine. If you are satisfied that you purged the system entirely of air after you replaced the pump, and believe me there is a procedure, and you checked with Ford parts department to see if there wasn't a change in the power steering hose design, my suggestion would be for you to replace the steering gear assembly at this point. Air is entering causing cavitation which causes the pump to whine.
It could also be a clogged or damaged catalytic converter. Suggest attempting to rev motor with transmission in neutral and engine at running temp. and see if there's a lack of higher RPM. If so, I would suggest attempting using a rubber mallet and rap the converter to see if there's any noise of loose pieces rattling inside, clogging the escape of exhaust gasses out the tail pipe. Check engine light on?
#1 heated Oxygen sensor is located on the exhaust manifold just before the flange to exhaust pipe inside the engine compartment. Look at the exhaust manifold nearest the firewall (dash). You'll see what appears to be a spark plug like devise that's screwed into the manifold near the flange that attaches to the exhaust pipe. It has an insulated electrical wire extending from its top.
they also had a problem with the fuel float making contact with a rubber pick-up hose associated with the fuel pump module, not allowing full swing of the float. Worth looking into...
Is it common for the rear brake pads to wear out after only 23.5k miles? No warning of impending damage to rotor via scrapper tabs...none notice on pads. Comparative front to rear pad surfaces, I still have approx. 80% lining left on fronts. Also noted significant pad size difference with the rears being much smaller pads. Possible design flaw given this vehicle is rear wheel drive with traction control? Or possible problem with electronic parking brake allowing rear brakes to drag. Anyone with input on this matter?