SOLVED! Electrical Gremlins

mateo

Member
Hi All, since I bought my 02 a year and half ago I have been battling with this electrical gremlin. It only rares its head from time to time so its been very hard to track down. I have gone through all the points I can think of going over all the manuals from Mooseman and still cant fig it out. Now I am sitting $3k into this problem with no AC due to it and its 109 out. I am hoping someone else has had these same issues and can help. Again its hit n miss when they come up but here are the issues...Driving the other night I turned on the brights and the engine stalled at 50 mph then I turn off brights and the engine runs fine. Same night I tried it again at full stop and it killed the engine. My left turn signal on the dash will glow dim solid on when I am having these issues and blink fast when left turn activated. Right turn is fine. Coming off a stop the engine will act like no throttle for about 1 to 2 seconds then pick up and run. Cruise works sometimes and sometimes not. Now my ac goes out and I put a new comp in it. That one was bad from the store so I take it to a shop to have it fixed. They tell me Im only getting 2.1v to the comp. I check things over and reseat the ground wires on the block and under hood. Replace fuse just to be safe and boom...14vdc. Take it in and they install new ac parts and good to go. 10 min of cold air then the comp clutch starts smoking. I take it back and they tell me there is a constant 5vdc to the clutch and again now my blinker is doing its thing. I have checked both fuse boxes and everything is fine. Checked the 27 point splice pack under dash along with every other ground that has SEEMED relevant to the issues with no luck. At this point I am thinking the B pillar grounds? Bad BCM or just replace the entire back seat box? New ECU? I dont know what else to do and I NEED this one to drive. Im driving a rental right now and cant afford any more out of pocket. Any advice would be much appreciated!
 

TollKeeper

Well-Known Member
This is a long shot, and just a suggestion. But usually with voltage drops I am looking for green crusties. And you having it across the board, in a lot of varying locations, there are 2 things I would start with. One is simple and free (assuming nothing needs repaired), and the other one does cost.

Remove the upper cover, and middle, of the fuse panel. This means unbolting those 4 brass looking bolts that are in the fuse panel. These will push out the bulkheads on the back, and allow for the middle fuse panel to be removed. Once the middle box is out, you are just doing a complete visual inspection of all the terminals, wire to terminal ends that you can see, and the back of the middle fuse block. Looking for green crusties (corrosion). Based on where you live, I doubt you will have any, but it may be worth a look since you dont know the entire history of the truck.

The other thing would cost, and thats a replacement of the ignition switch, if you already havent replaced it. Its fairly simple, and a fairly common problem for GM for all of the 2k vehicles.

Another thing to try would be to swap the AC Compressor Relay with an identical one from another location in your fuse panel. If may have a build up of carbon causing a voltage drop.

Lastly, are you running any LED lights?
 
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mateo

Member
Actually you may be onto something there. I was already thinking "I wonder if theres a short in one of my fuse blocks". No LED's. Im still a little baffled at why there are 2 fuse blocks (under hood and under back seat) on these but the one under the back seat seems to give a lot of headaches. I havent replaced the ignition in fact I didnt even take that into account but that is one part that ties it all together too. I have swapped the blinker brain box thing under the dash (cant remember what its called off hand) already as well as all the relays in the entire vehicle. I'll go check those out and see if theres any corrosion on the boards and see what all replacing the ignition entails. Thank you!
 

budwich

Well-Known Member
this thread had some similarities.... headlight and dying engine. Might give you some ideas on where to look and / or what to tell us about the history of the "area" on the vehicle (headlight replacement, switch replacement).


Having said, time to get out the meter. Since you can readily reproduce the event in a safe way (ie. no driving required). Gets some hand help to cause the problem while you monitor some power points.... such as the battery. Lots of tests: you indicate the stall happens but you don't indicate what happens at the dash in terms of indicators both for the engine and lights, what happens to the lights themselves, are the normal brightness, all working... etc

on the clutch "story"... it is somewhat "suspicious" as the clutch runs from putting 12v on it so 5v ain't going to cause much of a "direct problem"... possibly slipping as oppose to "full on". Again, not sure I understand what the 5v volt observation means. Have you personally check the voltage at the compressor?
 

gmcman

Well-Known Member
What is your voltage at 2000 RPM? Please check with a digital meter. Likely not an issue but I want to confirm you're not over charging.
 
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mateo

Member
How I love the rabbit hole effect. That link led me to 3 others and one that sounds very similar to my issues. Thank you budwich! To reproduce the issue is hard. I really lean toward a ground issue because here in Phoenix we dont have much if any moisture but after going through the car wash the issue will start or stop. Im thinking due to water grounding the ground? I love the gmtnation community. Its just awesome to hop on and ask for help and have so much of it!
 
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mateo

Member

gmcman I will check on that and get back to you.

This sounds like my issue however his has a few other things in it but the final outcome was still a ground problem.
 

MRRSM

Lifetime VIP Supporter
Specific to the Left Side of the Vehicle, there are Three Different Circuits sharing a Common Ground at the G-107 Position and as mentioned by @TollKeeper and @gmcman... any "Green Meanies" of Corrosion will INCREASE ELECTRICAL RESISTANCE just enough for the Fuel Pump Relay Circuit to suddenly drop out and Stall the Engine should the Electrical Draw from the Headlights and/or Left Turn Signal occur around the same time.

This Diagram shows how this can happen with a view of how All Three Circuits involving:

(1) The Left Headlight Wiring.
(2) The Left Turn Signal
(3) The Fuel Pump Relay

COMMONGROUND2.jpg

.... eventually all come together at the Common Ground of G-107 on the Engine Block:

G107.jpg

So Removing, thoroughly Cleaning and Re-Attaching that Ground and any associated Wire Connectors might stop this issue from happening.
 
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mateo

Member
FIXED!!! I know a little late but life has been a little crazy. Thank you all it was the G107 ground point. So I went through the ground points and the fuse box and more. I did have some minor corrosion on the circuit board but nothing to write home about. Cleaned it up. Tested the alternator and had great output from it to battery. Pulled and cleaned battery terminals. Then moved down to the ground points on the block. Pulled and cleaned all of them and found that the G107 point was lose and corroded. After a good dremil cleaning it was good to go. I also picked up an 18" 3/8 ground strap and installed it from the point on the chassis where the ground connects on the drivers fender well to the block. So battery to chassis to block is all grounded as one line now. For 2 weeks now driving it every single day testing out every possible scenario I have not had any further issues. I believe without a doubt it was the G107 point but I think adding the ground strap helped as well. Thank you guys for all the help and I hope this helps someone else in the future! Now to move on to other issues (BTW I have mastered how to pull the head without pulling the engine or losing timing but I will post pics of that in another write up) Cheers! 🍻 :2thumbsup:
 

MRRSM

Lifetime VIP Supporter
@mateo ... Please... Come back... and tell us-show us your :lightbulb: about "How to Pull the GM 4.2L Engine Head ...Without Losing Timing"
 
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