the switch is pretty cheap if you are not good with carefull about 16 bucks give or take. but if you have a diagram follow the path from the ignition start wire to the starter it is not a direct wire from end to end. but should give you a path to follow to see at what point your voltage drop is happening.

 

i had to lookup what U codes were as I have only ever seen P codes before. I have a cheapo $20 scanner that shows p codes and limited live data but I'm guessing it doesn't show P codes? Do you have to have a more advanced/expensive scanner to see U codes?

And our Hummer has a permanent CEL (or SES) light from the previous owner removing cats. So I wouldn't "see" the SES light for it. But I think the voltage is staying at 10v - 10.5 volts.....which might be just BARELY high enough to not trigger those things, but still cause intermittent starting.

I was waiting for a response earlier today and was just looking for anything I could find. I cleaned the 2 grounds that ground in the driver side front tow hook area but that didn't fix it. Watched a few troubleshooting videos and one showed how it could be ignition switch and another that it's common for mice to chew wires under fuse box. I wasn't sure how to remove/access ignition so I started taking fuse box out. I found some chewed up wires under there but didn't have a small enough socket (think 6mm) to get the last part out to get to them. Will get socket set in morning, try to repair, and report back. I'm truly praying this is the gremlin I been searching for.

 

I found some chewed wires under the fuse box but couldn't get to them yet to access and repair. Will get needed tools /wire tomorrow, repair and report back. If doesn't fix it, will do as you said. I don't know where to get diagrams from.....just Google it?

 

What about this test, it will take the trucks wiring out of the equation and tell you if mechanically things are working. Get some quality jumper cables and a known good battery or your other vehicle. Hook up one end of the cables to the spare battery, Negative to the starter motor body on your truck, positive to the battery cable lug on the solenoid, then got a wire and go from the spare battery positive to the S terminal on the solenoid, then it should spin the engine over each time you attach the hot wire to the S terminal. That should be a quick and easy test to see if the starter spins the motor.

 

Repaired the chewed wires under fuse box but that made no improvement in the starting issue. Had a feeling it wouldn't fix it purely because the wires weren't completely broken and none were in contact with anything (another bare wire or metal). So I figured they weren't actually shorting. My only hope was one of them being responsible for the slightly low voltage on the purple wire going to "s stud". (Which is only around 10.5 volts instead of 12)

 

what year is your truck, I don't remember seeing it listed?

U codes on a GM vehicle are usually loss of communications between the modules, this will happen when the voltage drops to low when cranking along with other causes
U codes are very common and usually will be shown on the low end code readers
Neal

 

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it's a 2003 H2. I just checked codes this morning and it still only shows the p0452 (I think it is) for EVAP system. I haven't ever seen a U code on this or any vehicle, but the PCM or one of the modules being bad is one of my worst fears I hope Is not the issue.

I plan to do the tests checking starter operation and flywheel through the plastic cover that fits around the starter tomorrow. (Sorry for being so retarded that I said it would take removing starter to do that test in previous message). I think the day in and day out worrying about fixing this truck is getting to me lol

I also plan to tackle the ignition switch tomorrow.

Is there any test I can do to confirm or eliminate the neutral safety switch?


Thanks so much as always Neal!

 

The neutral safety switch has to work if the small purple gets voltage but you can stick the truck in D or R and then try and start it to validate it defeats the starter.

Neal

 

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Ok, I tried to start it in other gears. In neutral it still makes the same 1 click at starter. In reverse or drive, it does not make the 1 click, showing that is functioning properly but I was actually more concerned about a pinched wire or something at the neutral safety switch causing the low voltage on the purple solenoid wire. (Same for ignition switch)

To recap after fulling charging the battery, it reads 14.3 Volts on my multimeter. In reality, it's 12.6 volts....my battery charger confirms it at exactly 12.6 volts when fully charged. (So that is 1.7 volts off)

To further confirm I tested voltage with truck running, it reads 16.6 volts while running, when in reality it's 14.4 volts. (That's 2.2 volts higher than actual). Reading were back to back. So that tells me the higher the voltage, the more it's "off" on the multimeter.

All this to say the voltage at purple wire, while trying to start, but it doesn't start.......is 12.1 volts. That reading has to be right around 1.5 to 1.7 volts off. So in reality I'm getting right at 10.5 volts on the purple wire............to me, this should be addressed first.......right?
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​​​​​​I still plan to do the visual inspection through the starter dust cover this afternoon, and possibly switch the ignition switch out just to see if it happens to be the issue. (Picked one up yesterday when picking up wifey from work for $25)

 

10 volts at the purple wire is low but not as critical as 10 volts at the main cable.
10 volts and below on either can and will cause starting issues, I agree with Bronxtech that over time the ignition switch contacts will get corroded and start dropping voltage.
Replacing the switch is not a bad idea but I prefer to test for low voltage closer to the switch as the neutral safety switch or the starter relay can also be the cause of low voltage at the starter on the purple wire.

You can take a jumper wire and jump from the large main cable to the purple wire which should supply full battery voltage to the starter solenoid. this how the remote starter button some use to troubleshoot works. You can buy them at the local parts houses usually. Its like having an ignition switch without the other safety switches inline.

Neal