Truck died while towing

[Chevy1925]

So my old girl (the truck lol) gave the wife and i a little scare this weekend.

Headed up north for the weekend with a full load on the back (5th wheel loaded with the tracker). pulling the hills i had no issues other than her getting warm up the hills. Soon as we finished the last hill, i had a good 2 mile 6% down hill on a 2 lane road. i was running 55mph which was the speed limit and would slow for corners. truck was doing its down grade shifting and was in 3rd gear at 3400rpm as we decended. Still needed some brake even at that rpm.

not a 1/4 mile into the down grade, abs/ebrake light flash, then flash again and gauges go nuts. Truck starts rattling and blowing white smoke so i throw it in N and turn the truck off all while still doing 55mph down hill. go to restart and i get nothing. so i start trying to alternate braking between the trailer and the truck. by the time we got to the bottom of the hill i was using all the brake i had in trailer and truck to get slowed to a stop and pull over. there was no coming to a stop coming down that hill. luckily i could get her slowed to about 40-45mph down hill and keep it there without riding things too hard initially.

So we get pulled off and i go to start it again. hit the key to start and nothing, not a sound. leave the key on run and all the gauges work, lights work, nothing shows being amiss. So i check all fuses inside and out with a test light and nothing is blown. find one bail connector is loose so i pull it, check pins and all looks good best i can tell. plug it back in and still no start. i would be throwing my efi live on it by now to check for codes but i left the damn thing at home (i never do this either, not happy at this point). so i pull the battery negative and unplug the trailer plug. leave it off for 30 sec and replug it all in. No start still. Now when i unplugged the batter, the glow plug controller started making some interesting buzzing noises. but once i unplugged the trailer from the truck, it stopped (obviously). Now i dont have any glow plugs in the truck and the wires for each glow plug are cut flush to the harness from when brian had the harness for his race truck. So no wires are touching anything. i unplugged the main power wire to the GPCM and try to start again. She fired right up! so i think the GPCM is screwing with the truck some how. the truck also turns over much easier and quicker now

We get all set back up and head on down the road. initially i had a ABS light when i first left but it shut off soon as i got to 15mph. figured it was from pulling the battery cable. we get about 10 min from camp and i loose converter lock up in 5th. still shifts fine but there is no lock up in 5th. so i down shift to 4th, same deal. i slowed to 45mph and it locked back up and stayed that way till we pulled off for camp. thought that was strange.

now we leave to go back home and all seems to be good. again, ABS light back on after start up till i hit 15mph so i figure i have a hurt wheel speed sensor from my major braking or a wheel bearing dieing. we come to a long 9 mile 6% grade with winding 2 lane. again, down grade shift to 3rd gear and am up to 3500-3600rpm. all is great till i come to a lull where i im running about 52mph in 4th gear under some throttle. i click the tow/haul button to let the truck up shift to 5th and as soon as i click it, same shit starts to happen again but i immediately hit the tow haul button again and it stops doing it and runs fine. never did it again on the way home or the rest of the way down the hill.

its a hell of a long shot but anyone had this happen before? its got to be electrical whether i have a hurt TCM/ECM or something else? there are no burnt wires, no cut ones. checked the normal LLY wear through spots and nothing i can see. definitley not the "ice pick" issue has ive had that happen and its no where near this dramatic. i posting this with me not having much diag done on the truck yet so i know im missing some info that might help.

 

[Hoffie]

That sounds like a scary ride indeed. I wish that I had an answer for you, but my truck has not done that yet. I get traction control light on from time to time on those curvy roads going to Payson and back when I have my trailer hooked up. Luckily, no ABS light. The only thing that I have had happen was the TCM wiring harness came loose in the transmission pan and fluid got into the wiring harness and shorted out 5th and 6th and the TCM. The dealership replaced the harness, TCM, trans fluid, both filters and both 5th and 6th solenoids - $2000.

 

[DAVe3283]

The GPCM could well have been screwing with the truck. It shares the CAN bus with the engine & transmission computer, and if it is spamming garbage (or electrical noise/signal degradation) onto the bus, it could cause all your issues. If you don't have glow plugs, I would remove the GPCM entirely, and put a terminating resistor across the CAN bus. If it is the LLY controller, it is C2, pins 6 & 12. I don't know what resistance should be used off the top of my head, but Ben might.

 

[Chevy1925]

Thanks dave! i really hope its just that. ill try just unplugging it without the resistor and see what kind of crap i get.

 

[Chevy1925]

Unplugged the GPCM before I headed home, no check engine light. Every time I go wot though, truck dies out, comes back very quickly and abs/ebrake light come on. Checking for codes in a few.

I have a bad thought in the back of my head of a hurt crank.....

 

[02greysixer]

My lly did some weird things and would never set a dtc. Cutting out at higher rpm, no starts randomly, odd shifts etc. Finally I got a crank sensor code when it wouldn't run at all and put a sensor in it on a whim. Fixed it.

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[NC-smokinlmm]

I bet bad tcm...

My lmm did freak out once and cut off, it only threw a crank postion code. I atributed it to the banks system conndctions. It happened in a busy intersection, had to remove the banks just to get it to start...

 

[Chevy1925]

Yeah it's pretty repeatable at wot, after I check for codes, I'll log it and see what I come up with. I red loctited the reluctor wheel so I know it didn't come loose

 

[Chevy1925]

Here are the codes

Before I tried clearing them

After clearing and rechecking. Truck was cold (just started for the morning) and did not move between clearing and rechecking

Kinda thinking tcm or wiring loom has an issue

 

[Chevy1925]

Figured it out. What a god damn pain in the ass....

Went over to Steves to pick up some parts, shut truck off and went inside. Came out and went to fire it up only to have all kinds of crazy things start happening on the dash. Lights were dim, service 4x4 was on, fuel gauge quit, no CEL with Key on engine off and no crank.

Steve and I spent the next 6 hours tugging wires, tracing things, jumping wires, swapping things around till I ground the ECM to the battery. Then the gauges acted normal but no crank still. Tried jumping the starter terminals and nothing. Even with Steves truck hooked to mine for battery boost. So put a new starter in. Still won't start with the key but jumping posts on the starter makes movement though the battery is weak now. As I'm messing with it, I see a ground has broke off at the harness that is tied into the starter wire. Son of a bitch, there is my issue I've been having. Then find my battery is dead. So tried jumping it but could not get enough power to the truck. Spent an hour dicking with it till I finally went back and got a new battery.

It seems the ground being broke made the starter draw power. This battery wasn't in the best shape and I think it finally died. Starter was original to the truck so the constant current must have killed it. I'm sleep deprived right now so if this don't make sense, I'll try to clear things up in the morning.

The main things is the damn truck is back up and haulin ass again. No issues all the way home with a few WOT passes

 

[duratothemax]

Hmmm...where did the ground break? Did the terminal rip off? Did it look like the wires were run tightly that might have stressed it? I always replace any ground terminals that look suspect.

It would be a good idea to clean the block too, where the ground attaches.

You dont need a terminating resistor when removing the GPCM on an LLY. The ECM and FICM both have (120 ohm) terminating resistors built into them. CAN only needs two 120-ohm terminating resistors (for 60 ohms nominal) across the hi/lo differential wires , on either end of the circuit...as long as those two resistors are there, you can add or remove any extra nodes (modules) that you want to, as long as you dont remove the nodes that have the built in terminating resistor......obviously you'll never remove the ECM or FICM.....

So just leave it unplugged and put some tape around the connector to prevent the terminals from corroding. Or leave it hooked up, doesnt really matter.

 

[JoshH]

Figured it out. What a god damn pain in the ass....

Went over to Steves to pick up some parts, shut truck off and went inside. Came out and went to fire it up only to have all kinds of crazy things start happening on the dash. Lights were dim, service 4x4 was on, fuel gauge quit, no CEL with Key on engine off and no crank.

Steve and I spent the next 6 hours tugging wires, tracing things, jumping wires, swapping things around till I ground the ECM to the battery. Then the gauges acted normal but no crank still. Tried jumping the starter terminals and nothing. Even with Steves truck hooked to mine for battery boost. So put a new starter in. Still won't start with the key but jumping posts on the starter makes movement though the battery is weak now. As I'm messing with it, I see a ground has broke off at the harness that is tied into the starter wire. Son of a bitch, there is my issue I've been having. Then find my battery is dead. So tried jumping it but could not get enough power to the truck. Spent an hour dicking with it till I finally went back and got a new battery.

It seems the ground being broke made the starter draw power. This battery wasn't in the best shape and I think it finally died. Starter was original to the truck so the constant current must have killed it. I'm sleep deprived right now so if this don't make sense, I'll try to clear things up in the morning.

The main things is the damn truck is back up and haulin ass again. No issues all the way home with a few WOT passes

If I'm understanding correctly, the wire you're talking about is actually the ECM ground.

 

[Chevy1925]

jesus that post of mine is all over the place lol.

Long story short, Ground that is in the same harness at the starter signal wire broke at the block on the passenger side, Starter directly shorted internally, killed battery. I do not believe the starter shorting was fully caused by the loss of the ground but it may have done the old starter in finally. Had to buy new battery, new starter and fix ground after hours of wire chasing and pulling things apart.

Hmmm...where did the ground break? Did the terminal rip off? Did it look like the wires were run tightly that might have stressed it? I always replace any ground terminals that look suspect.

It would be a good idea to clean the block too, where the ground attaches.

You dont need a terminating resistor when removing the GPCM on an LLY. The ECM and FICM both have (120 ohm) terminating resistors built into them. CAN only needs two 120-ohm terminating resistors (for 60 ohms nominal) across the hi/lo differential wires , on either end of the circuit...as long as those two resistors are there, you can add or remove any extra nodes (modules) that you want to, as long as you dont remove the nodes that have the built in terminating resistor......obviously you'll never remove the ECM or FICM.....

So just leave it unplugged and put some tape around the connector to prevent the terminals from corroding. Or leave it hooked up, doesnt really matter.

its nothing you missed, ben. i may have worked the ground over some when i did the swap. i know i was working the ground ends around to get everything ran nice, might have cracked it then. it was an old terminal on there originally. grounds were all cleaned up when i did the swap and still looked clean enough to eat off of, nice part of living in AZ and the truck sitting in the garage most of the time

im going to put the GPCM back in as the real issue was the ground, i believe unplugging the GPCM and the truck starting was coincidence when it first happened since there is no signs of bad wires after we torn things apart yesterday.

If I'm understanding correctly, the wire you're talking about is actually the ECM ground.

that would explain why grounding the ECM body out would make everything go back to normal. lol

 

[JoshH]

that would explain why grounding the ECM body out would make everything go back to normal. lol

I didn't realize you had been work your harness over. As long as he didn't move the factory ground location, the ECM grounds to the block at the front right side of the block in forward-most lower hole with the negative battery cable. If that's the one you're talking about, that's what it is. It's funny you had this happen because I just had a similar issue with a truck we were working on here, and I was going to suggest you check that wire but saw you had already figured it out. :thumb:

 

[c20elephant]

I forecast a new 2016 LML towing rig in your future before they're all gone, older trucks take on a life of their own and yours. I sold my work truck after almost 25 years awhile back....:thumb:

 

[Chevy1925]

I didn't realize you had been work your harness over. As long as he didn't move the factory ground location, the ECM grounds to the block at the front right side of the block in forward-most lower hole with the negative battery cable. If that's the one you're talking about, that's what it is. It's funny you had this happen because I just had a similar issue with a truck we were working on here, and I was going to suggest you check that wire but saw you had already figured it out. :thumb:

that is exactly the one im talking about. you change that ground/loom out when you do the LLY swap that incorporates the LLY ECM. i hate wiring issues lol

I forecast a new 2016 LML towing rig in your future before they're all gone, older trucks take on a life of their own and yours. I sold my work truck after almost 25 years awhile back....:thumb:

Na, The Limo wont go anywhere. the only issues i have had on this truck are ones ive caused. the ONLY time its left me on the side of the road and not being able to fix it was on a trip back from denver when i lost a wheel bearing 30 min outside of Vail and even then, a tow into the nearest NAPA, i swapped wheel bearings in the parking lot and off we went. in a 15 year run, id say thats a great track record. it may not be 100% some times getting us home but always does.

now all that said, i know shes old. Wife and i are waiting till the new trucks hit 500hp. then we will be selling her canyon and buying her a new dmax that i will use for towing (yes she ok with that compromise ). Ill still be keeping The Limo though.

 

[Dozerboy]

You ever sell it there will be a line of people that want it.

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[Chevy1925]

You ever sell it there will be a line of people that want it.

Sent from my SAMSUNG-SM-G900A using Tapatalk

and it will have to be someone out of state never planning to come back to AZ and never posting on this forum. :roflmao:

 

[c20elephant]

that is exactly the one im talking about. you change that ground/loom out when you do the LLY swap that incorporates the LLY ECM. i hate wiring issues lol



Na, The Limo wont go anywhere. the only issues i have had on this truck are ones ive caused. the ONLY time its left me on the side of the road and not being able to fix it was on a trip back from denver when i lost a wheel bearing 30 min outside of Vail and even then, a tow into the nearest NAPA, i swapped wheel bearings in the parking lot and off we went. in a 15 year run, id say thats a great track record. it may not be 100% some times getting us home but always does.

now all that said, i know shes old. Wife and i are waiting till the new trucks hit 500hp. then we will be selling her canyon and buying her a new dmax that i will use for towing (yes she ok with that compromise ). Ill still be keeping The Limo though.

Have to admit I was close, Took me almost 2 years before I posted and sold the elephant. The wife had questioned me about selling, NO. I just up and one day without telling her put it up for sale.

Guy called me a few days later and said he would be come by the next day. I told the wife that night next day offered a few hundred dollars less than what I was asking and off to the bank with him and sold. The new owner lives about a half mile from me seen it cruising a few times since....

 

[Burn Down]

I hate those ground wires James:rofl: The upper one, if loose will make the truck rattle and knock like crazy Took me close to a year to find it, so intermittent at first...