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Discussion Starter · #1 · (Edited)
I posted 23 days ago and still am at a loss for my problem... I have added new brass battery terminals, cleaned battery to engine ground wire... Swapped out fuse panel relays... Disassembled, cleaned and used di-electric grease on inner fender ground connectors (both sides) and a new battery... No gain in my issue! I am looking to change ignition switch next as I seen GM had a recall on ignitions switches failing and shutting off the vehicle! But, my "loss of power" can happen while the truck is just "setting still in the driveway" not moving! I found tonight when it happened that if I JUST let it set with the key off, it would restart after a period of time! I was unhooking the battery and re-attaching the cable before... I can even just turn key to on position and the problem happens, it won't start... Any help is so appreciated! It's like something is getting hot (like a circuit breaker) that shuts the electrical off and then restarts after it cools off... I am at a loss with a truck I love so much!

* There are times where I drive 20 miles to work with NO problem... 馃槩
 

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Discussion Starter · #3 ·
When you say it restarts, you mean the starter actually spins up on its own? Do you have an aftermarket remote start?
Yes, as a matter of fact... I changed out the ignition switch today after it quit on me 5 times every 6-7 minutes like clockwork. While I had the column and panels off I was staring at the installation of the aftermarket auto start. It does work fine when I use it as the only feature is start & stop the truck. Every time it lost power while driving I got out and disconnected the battery and re-attached and it started right up with NO hesitation... I also went through the passcode procedure and after the 3rd cycle the truck did shut off on its own before it completed the 10 minute waiting period! But, then it started right up as it said it should! So weird... Why do you say remote starter? I did not install this, it came with the truck... Thanks for the reply
 

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Discussion Starter · #4 ·
Yes, as a matter of fact... I changed out the ignition switch today after it quit on me 5 times every 6-7 minutes like clockwork. While I had the column and panels off I was staring at the installation of the aftermarket auto start. It does work fine when I use it as the only feature is start & stop the truck. Every time it lost power while driving I got out and disconnected the battery and re-attached and it started right up with NO hesitation... I also went through the passcode procedure and after the 3rd cycle the truck did shut off on its own before it completed the 10 minute waiting period! But, then it started right up as it said it should! So weird... Why do you say remote starter? I did not install this, it came with the truck... Thanks for the reply
If you are asking does the starter have a mind of its own? No... It's like something "resets" itself and it goes back to a normal start up. Without removing the battery cable for a brief period of time, when you turn the key the lights are normal, but the radio display and heater fan slow down or the display goes blank... Thanks
 

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Most remote start systems have an timed shutoff (so you don't inadvertently start your car remotely while leaving for a one week vacation in another car...) - 10 minutes is notional for those timers, but 6-7 minutes might be what your system does. So that system can turn the car off as well, and they do fail when they get older. I think your truck is running on the remote start timer all the time, and it does what it's supposed to do and turn the engine off after a fixed period of time. I'd pull that system out and see if things become normal.
 

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Discussion Starter · #6 ·
Most remote start systems have an timed shutoff (so you don't inadvertently start your car remotely while leaving for a one week vacation in another car...) - 10 minutes is notional for those timers, but 6-7 minutes might be what your system does. So that system can turn the car off as well, and they do fail when they get older. I think your truck is running on the remote start timer all the time, and it does what it's supposed to do and turn the engine off after a fixed period of time. I'd pull that system out and see if things become normal.
I like the idea and will disable tomorrow... Thank you so much! I'll post the outcome for you & others
 

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Discussion Starter · #7 ·
I like the idea and will disable tomorrow... Thank you so much! I'll post the outcome for you & others
Well, it's a "new day" with an old problem as stated above... I went to leave at 4:30am for my drive to work... Truck would turn over but not even start! Never had that before... Made my workplace (on time) and then got back home by a co-worker. I disabled (took out 3 fuses the installer had put inline) my aftermarket auto car starter that I paid "dearly" for was now dead... I went back through the procedure to reset the PASSLOCK system as yesterday. After installing a new ignition switch yesterday, doing the same, at the 3rd round of the procedure I realize that my truck had defaulted (key in on position) and the electronic password never happened! So, this time (with a stopwatch in hand) I went through the sequence and the last 10 minute time frame went as it was suppose to and the truck started! I was relieved and thought I better leave it run. I was beyond excited! Then my wifey asked me later if I had shut the truck off, only to realize after 12 minutes it was dead again! I went out, turned the key and no start, no starter engagement. The instrumentation was "on" inside. I went out under the hood, removed the battery cable reinstalled after 5 seconds and it started as usual. I know America is a "great nation" I just hope that someone out there in 355 Nation.net can help me through this! Thanks Kenzen, I thought we had it!
 

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Ok...just some guessing here on what to look at. First lets make sure you have solid power to the circuit that starts and keeps the truck running.
1. Relay 61 is the Run/Crank Relay that would be a primary source of power to the BCM to keep the truck running - swap it or replace it.
2. Ground G105 (or SP105) is a common ground point for the BCM that is the ground point for (among other things) the Run/Crank Relay. It's located outboard your battery, bolted to the fender. This is a known source of weird electrical problems - take it off and clean it up - make sure there's solid metal to metal between the lug and the fender. (There's another "twin" to this on the other side of the engine compartment - clean that one up as well "while you are there".)

Did you remove the remote start connections from the ignition system, or did you just pull the fuses?

Lets see if 1 & 2 above address the problem. Sometimes a relay with pitted connections inside will effectively open as it warms up, which would give a delay to the effect of its failure. The ground point can behave the same way.
Ken
 

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Man these problems are frustrating. I had a similar problem in that I had a no start when cold. Below ~32* my truck would crank but not start. 34 and above, non issue. Through trial and error I learned that if I heated up the fuse block with a hair dryer, truck would start. Eventually I narrowed it down to the TCM fuse that has a sloppy socket. I found that by wiggling each fuse while the truck was running. Wiggled that fuse, and it died. Do your reset method and poke each fuse and relay, see if you can find one to respond.
I need some clarification please. Does this happen while the truck is in gear and moving, or is it always while idling for X minutes. If only an idle issue it sure seems that the auto start is not executing the handshake to say you have key started the truck.
 

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Discussion Starter · #11 ·
Ok...just some guessing here on what to look at. First lets make sure you have solid power to the circuit that starts and keeps the truck running.
1. Relay 61 is the Run/Crank Relay that would be a primary source of power to the BCM to keep the truck running - swap it or replace it.
2. Ground G105 (or SP105) is a common ground point for the BCM that is the ground point for (among other things) the Run/Crank Relay. It's located outboard your battery, bolted to the fender. This is a known source of weird electrical problems - take it off and clean it up - make sure there's solid metal to metal between the lug and the fender. (There's another "twin" to this on the other side of the engine compartment - clean that one up as well "while you are there".)

Did you remove the remote start connections from the ignition system, or did you just pull the fuses?

Lets see if 1 & 2 above address the problem. Sometimes a relay with pitted connections inside will effectively open as it warms up, which would give a delay to the effect of its failure. The ground point can behave the same way.
Ken
1 & 2 I had already disassembled and cleaned grounding points on each fender area and mounting bolts... They "looked" fine, also applied a touch of di-electric grease before pushing spade(s) back together in plastic housing... Already changed relay with a new Delco brand... 3 I just removed the 3 fuses that were installed inline, did not cut wiring... Heading to work soon this morning, hopefully it starts! Funny my 20 mile commute to work it gets there (it has died once in three weeks), when I head home in the afternoon it dies on and off in intervals. It still acts like something heats up and opens electrically. :unsure:
 

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Discussion Starter · #12 ·
Man these problems are frustrating. I had a similar problem in that I had a no start when cold. Below ~32* my truck would crank but not start. 34 and above, non issue. Through trial and error I learned that if I heated up the fuse block with a hair dryer, truck would start. Eventually I narrowed it down to the TCM fuse that has a sloppy socket. I found that by wiggling each fuse while the truck was running. Wiggled that fuse, and it died. Do your reset method and poke each fuse and relay, see if you can find one to respond.
I need some clarification please. Does this happen while the truck is in gear and moving, or is it always while idling for X minutes. If only an idle issue it sure seems that the auto start is not executing the handshake to say you have key started the truck.
My problem happens with "both" scenarios... Setting & going down the road. Two days ago while traveling it had power loss every 7-8 minutes in 35 minutes of driving. I knew this as when I removed the battery cable the re-installing the radio clock would reset to 12:00. Again, before I took the cable off and turned the key there was NO click or restart! Instrument lights were on and no dash icons flashing...
 

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Discussion Starter · #15 ·
What remote start system was installed? I'm curious what modifications to the wiring harness it takes to install it - I'll look up the install manual online.
Crimestopper RS4-G5-1 Way unit installed 12/20/2018... I left for work early AM, never had issue in 20 miles... Got out headed home and no issues... Left run in driveway and roughly 12 minutes later it shut off! Sad thing is my PASSLOCK light stays on now (it was on this AM when I started the truck...) I've reset it twice again since and now I can't even get it to flash as procedure says it should and truck starts every time! I left it run then and it shut off in 5 minutes... I have completely removed the crimestopper (beyond just fuses) main module under dash. I called the place that installed and first he said they didn't sell them that long ago... I gave him the invoice number and he changed his attitude! He told me to unhook this module... I don't understand how a harness as this can just be hanging there with nothing on it now and it still runs! I can't see if they added a cable to a GM plug-in under the dash in the darkness? Anyway, I left the battery cables tied together off the battery. I need a break... Some say it helps... ???? The other info as I stated before is that when it quits (in my driveway) and I let it sit 5-10 minutes it will crank and start again! I don't have to unhook the battery cable... It's like there's a resetting circuit breaker some where that opens and closes when it cools off! Man, I'm stumped!
 

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Just thinking out loud here - I don't think this has anything to do with the PASSLOCK system - that only disables the fuel delivery while starting, it would still turn the starter and power everything else up. You changed the ignition switch, which assumes you'll need to do the PASSLOCK relearn, which you seem to have successfully done.

1. When the truck dies, does it seem to be a loss of fuel (sputters to a stop), or a loss of ignition (instant loss of power)?
2. What idiot lights come on on the dash when it dies? Or are you losing the lignts on the dash as well? I'm finding it strange you don't get a CEL on these shutdowns.
3. Not all engine faults trigger a CEL - do you nave the ability to scan the OBD2 port?

The fact you have to disconnect and reconnect the battery to get the starter to respond is a key fact here....need to think this through...(deeper thought - is there a master auto reset breaker for the power to the fuse box...I don't think so...but maybe a fusable link that's buggy.)

As Dragon08 stated above - fuse connections can make these problems occur: Inspect/replace fuses 30 (PCM B), 20 (ETC), 23 (IGN), 25 (PCM 1) and 22 (INJECTOR). Get a can of electrical contact cleaner to spray in the fuse slots.

Replace Relay 56 (POWERTRAIN) if you haven't already.

I have to dive into the connector diagrams now...
 

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Discussion Starter · #19 ·
Just thinking out loud here - I don't think this has anything to do with the PASSLOCK system - that only disables the fuel delivery while starting, it would still turn the starter and power everything else up. You changed the ignition switch, which assumes you'll need to do the PASSLOCK relearn, which you seem to have successfully done.

1. When the truck dies, does it seem to be a loss of fuel (sputters to a stop), or a loss of ignition (instant loss of power)?
2. What idiot lights come on on the dash when it dies? Or are you losing the lignts on the dash as well? I'm finding it strange you don't get a CEL on these shutdowns.
3. Not all engine faults trigger a CEL - do you nave the ability to scan the OBD2 port?

The fact you have to disconnect and reconnect the battery to get the starter to respond is a key fact here....need to think this through...(deeper thought - is there a master auto reset breaker for the power to the fuse box...I don't think so...but maybe a fusable link that's buggy.)

As Dragon08 stated above - fuse connections can make these problems occur: Inspect/replace fuses 30 (PCM B), 20 (ETC), 23 (IGN), 25 (PCM 1) and 22 (INJECTOR). Get a can of electrical contact cleaner to spray in the fuse slots.

Replace Relay 56 (POWERTRAIN) if you haven't already.

I have to dive into the connector diagrams now...
!. When it dies it just shuts off... No feeling of sputter nor surge
2. Lights remain same with no extras coming on...
3. I have a OBD2 and only codes are o2 sensors that I have replaced one at lower, but waiting on offset socket that hasn't came to change upper. Also have emission canister blah, blah, but read that once o2 sensors are changed it will go away...
4. I re-seated all fuses and relays in fuse block, seen no corrosion & is very clean. Switched relays around to areas that are associated to starting/running... I will use contact cleaner tomorrow in fuse block, mine is LPS brand so it doesn't melt nor harden the plastic.
 
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