Hello All,

I've been working on this problem on and off for months and need some help.

Vehicle:
2007 Silverado Classic 4WD 210,000 mi

Problem:
When it began, I would drive the vehicle like normal, park and turn it off (say to get gas), and then when I would turn the ignition I'd hear a "click/snap" and the whole vehicle would die. No power (no clocks, lights, IP, nothing), no cranks, not even the click that started the problem. I replaced the battery (because it was aging) and that solved the problem for a few days. Ultimately, this problem returned. Auxiliary power came on, turn ignition to hear a single "click/snap" and the whole system dies. Once the click happens there is no power to anything. I charged the battery and again the problem went away for another month or so before returning. Now, it has happened again. This time, charging the battery doesn't allow me to get auxiliary power back.

Symptoms/Checks:
I began by checking all fuses related to the ignition system for continuity. Based on comments from the local NAPA, I was told it could be an arc which was shorting and that was the snap I heard, but to check other electrical components first. Battery and fuses were good; I pulled the starter solenoid and tested it which looked and sounded great. Here is the kicker, I couldn't directly test the starter relay with my equipment, but I could jump it to make sure the starter portion of the ignition circuit was working. Jumping the starter relay does not induce the starter to run. Plus, I read a clean 12.6 V at pin 30 of my relay which tells me I've got a good connection back to the battery. A possible idea is the harness between the relay and starter is questionable, but I haven't verified that.

After realizing this I jumped to the ignition switch portion of the system. I pulled the ignition switch and tested continuity between all the pins and shims inside the switch, everything sounded good. Once I reassembled the switch, I tried to test the ignition with no luck. Here I started going around to find all my ground points and clean them up. During this process, (which I have yet to start cleaning) I returned to the key and turned it to find that the auxiliary power works again! I have no clue what changed to complete the circuit; however, I was short sighted and tried to turn the ignition which led to the fated "click/snap" and everything went away again. I should have left the auxiliary power on to pull a code but now I have to wait.

At this point, I need to clean my grounds, verify voltage at the main battery cable leading to the starter from the relay, and then I think start testing other modules like the BCM (which I know plays into the ignition switch circuit but don't have a full ignition system schematic to know for sure). I've also been told when I have power again, to try turning the ignition late at night and look for a bright light from an arc from under the truck. I've been told this might help me locate a short. The problem seems to be between the ignition switch -starter relay-starter but I haven't been able to narrow it down yet.

My goal is to diagnose the problem without outright replacing parts blind, but I'm beginning to run out of options. Any help figuring this out would be amazing.

Thank you kindly ~ Cody

 

Welcome from Florida. Did you check both battery cables for tightness and corrosion at both ends?

 

You may also have internal cable corrosion you can't see - remedy is replace the cables.

 

I did, one of the first things I did when I bought a new battery I cleaned the cable connectors (side post) and tested voltages on both the battery posts relative to each other and relative to the grounded frame.

 

I'm worried about that, I've been trying to test the various cables. Would a voltage test be able to capture that or is it possible for there to be corrosion that reads normal voltage but can't accommodate the current during ignition?

 

A bad cable wil somtimes not be able to handle the current draw the starter calls for.

 

I think you called it here. Below were some updates from another forum I was checking. It was getting enough current from time to time to run the minor systems but didn't have the contact it needed to engage the starter. I never saw sparks at the post though and for the life of me don't know how it did this on its own (came loose enough to cause problems that is). It drove fine for weeks before this problem arose last time. I'm wondering if my threads are just worn on that side post connection and vibrations were causing it to come loose over time. I'll keep an eye on it to see if it happens again. Regardless I appreciate all the help, it definitely got my mind pointed in the right direction!

Update - this morning I went out to test a few things and turned the key over to auxiliary with no power. I forgot to turn it back off (got distracted). I was going to attach a jumper cable to the battery. I attached the positive jumper to the positive post and BAM, my fans and auxiliary power turned on. I was able to reliably turn on auxiliary power but when I turned the ignition I heard the fated "click" and everything died. Now the same procedure doesn't induce the auxiliary system to turn on. I'm guessing I have a grounding issue, and maybe a short is draining the battery with each click? I'm charging the battery now to see if I can replicate the issue.

Update - (last one hopefully) I charged the battery and didn't get power; however, I realized there was some play in the positive post. When I jimmy'd the post I got the power to kick on. When I tightened the post down the power comes on AND TURNs OVER. I'm in disbelief at this point that my problem is a poor connection at the battery because I thought I checked that. I'm not sure why it would be doing it on its own except for maybe the treads are worn and loosen over time while driving. That being said I appreciate all the help, things seem to be on the up!

 

I'll be honest I thought I had checked for tightness since I had just taken the battery our and put it back in but a poor connection at the positive post was the answer. That being said I don't know how it happened on its own from driving months ago but at this point I'm happy it turns over. I appreciate the help!