Please Help - Intermittent Stalling

[rugz31]

Hello all,

 

I've been having some issues with my 2014 Silverado randomly stalling on me for the last couple months. Seems to happen more frequently after heating up. At first, it would usually run for 2-3 hours before stalling, but now it seems to be getting more frequent, maybe every 30 minutes to an hour. It will stall while idling or while under load. I've checked 12v battery several times at different places, everyone tells me the battery is good. I've checked cable connections, battery ground, etc and found no issues. I've gone over the fuses and didn't find any that were broken.

I hooked a VCX Nano up to the truck and these were the codes it pulled: U0101 Lost Communication with TCM, U0121 Lost Communication with Electronic Brake Control Module, P0621 Generator L-Terminal Circuit. I attached the DTC log from the VCX Nano if that's any help.
 

Here's the catch: the truck was converted to an aftermarket Plug-in Hybrid by VIA Motors making diagnosis even trickier for me. The truck stalls while running on battery power and on ICE generator. I'm not sure how relevant these codes are to what I'm dealing with. For instance, the U0101 code seems to be irrelevant because the truck doesn't have a TCM or a transmission. I'm leaning toward an electrical short or bad ground somewhere or possibly ECM failure? Does anyone else have any ideas what could be causing my issues?

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[Snowcamo]

I really am interested in a vehicle without a transmission. Can you elaborate on the hybrid swap? 

[LDM]

My 2018 would just randomly die while turning for no apparently reason.  Ended up being the negative battery cable.  After replacing it in the summer of last year I haven't had an issue since.  I know your truck has a lot more going on with the swap but I would start with the grounds and then swap that if it still does it.  Seems like there are a lot of issues with the factory negative battery cables and sensors on the 14-19 trucks.

[rugz31]

1 hour ago, Snowcamo said:

I really am interested in a vehicle without a transmission. Can you elaborate on the hybrid swap? 

Sure. So it's essentially been turned into an electric vehicle, it uses electric motors to drive the wheels. The ICE is used as a generator to recharge the HV system. The HV system runs for between 30-50 miles on battery power alone, when the battery drains to about 20% it kicks the ICE generator on to drive the system. It's weird to drive because the engine revs don't match when you put your foot on the gas, it revs when the HV system determines it needs more power. It's pretty strange to drive until you get used to it. I can't give a whole lot of specifics because I'll be honest I don't really understand much of it that well either. I just know the bellhousing, TCM, starter, alternator, and several other parts were removed to add the hybrid drive system.

The chairman of the company who did the conversion, VIA Motors, is Bob Lutz who I'm sure a lot of you are aware of. He did an episode of Jay Leno's garage a couple years ago to showcase the truck. Here's the clip from the show if anyone is interested.
Jay Leno's Garage- VIA VTrux

[rugz31]

1 hour ago, LDM said:

My 2018 would just randomly die while turning for no apparently reason.  Ended up being the negative battery cable.  After replacing it in the summer of last year I haven't had an issue since.  I know your truck has a lot more going on with the swap but I would start with the grounds and then swap that if it still does it.  Seems like there are a lot of issues with the factory negative battery cables and sensors on the 14-19 trucks.

I have checked for voltage drop from battery post to the negative cable clamp and there's no drop. Maybe it drops in a different part of the cable? I checked the ground to the block and it seemed good, but I'll give this another look.

I forgot to mention a few other specifics about the stalling. I don't lose power to radio, dash lights, interior lights, etc. The engine just stops running, everything else works fine except heater/AC blow room temperature air (air temp can't be controlled through dash thermostat). One time when this happened, I did have lights on the dash saying "battery saver active" and "battery low- start vehicle." Only one out of probably 20 times it's stalled that I've gotten these messages. The rest of the time, it might give stabilitrak or security messages. When it stalls, it won't start right back up, it has to sit for several minutes or sometimes hours before it will start back up and give me the "ready" signal to drive.

I had thought it was the ignition switch originally because the truck acted like somebody just turned the key off. Changed that but it didn't help.

[LDM]

50 minutes ago, rugz31 said:

I have checked for voltage drop from battery post to the negative cable clamp and there's no drop. Maybe it drops in a different part of the cable? I checked the ground to the block and it seemed good, but I'll give this another look.

I forgot to mention a few other specifics about the stalling. I don't lose power to radio, dash lights, interior lights, etc. The engine just stops running, everything else works fine except heater/AC blow room temperature air (air temp can't be controlled through dash thermostat). One time when this happened, I did have lights on the dash saying "battery saver active" and "battery low- start vehicle." Only one out of probably 20 times it's stalled that I've gotten these messages. The rest of the time, it might give stabilitrak or security messages. When it stalls, it won't start right back up, it has to sit for several minutes or sometimes hours before it will start back up and give me the "ready" signal to drive.

I had thought it was the ignition switch originally because the truck acted like somebody just turned the key off. Changed that but it didn't help.

I didn't lose any of those things either one mine, the engine would just die out.  It only seemed to happen while turning, which was also strange.  I spent some time cleaning up the grounds and making sure they were all clean and secure.  None of that seemed to help so I ended up just getting the entire negative battery cable assembly.  After that I haven't had a single issue.

 

I know yours is going to be a bit more complicated due to your hybrid setup.  But considering that a negative battery cable assembly is only around $80, I would do that first.  Not sure if it was a bad batch of these or what but I'm not the only one that has done this and had it fix weird issues like this.  I even ohmed out the cable and it didn't show any different than the new cable.  Maybe the sensor was causing the issue?  I'm not really sure.

[rugz31]

7 minutes ago, LDM said:

I didn't lose any of those things either one mine, the engine would just die out.  It only seemed to happen while turning, which was also strange.  I spent some time cleaning up the grounds and making sure they were all clean and secure.  None of that seemed to help so I ended up just getting the entire negative battery cable assembly.  After that I haven't had a single issue.

 

I know yours is going to be a bit more complicated due to your hybrid setup.  But considering that a negative battery cable assembly is only around $80, I would do that first.  Not sure if it was a bad batch of these or what but I'm not the only one that has done this and had it fix weird issues like this.  I even ohmed out the cable and it didn't show any different than the new cable.  Maybe the sensor was causing the issue?  I'm not really sure.

That's good to know, thanks for your input! Maybe I'll give that a shot tomorrow. I have a circuit test tool supposed to be delivered tonight so I can check relays and wires and stuff to see if there's a short somewhere. It's supposed to tell me if I have a bad ground as well.

Really have my fingers crossed for a simple fix like negative battery cable. I've been planning on selling the stupid truck after I get it fixed as it's been a huge pain trying to get VIA to help diagnose the problem. Carvana gave me an offer $6.5k higher than I paid for the truck 8 months ago. I got a helluva deal on it at the time, $15k with only 17k miles. I guess people got scared by the hybrid system, and now I completely understand why. I just would hate to sell it when it only has 17k miles on it. If it's such a simple fix, I might reconsider my plan to sell.

[rugz31]

I don't know if this helps at all, but I spent a little more time messing with things on the truck tonight. I let the truck idle in my driveway until it stalled out, approximately 30-45 minutes. When it stalled, I turned the key off for a few seconds and then tried to start it back up. I tried several times, no luck. My next step was I disconnected the battery and touched both cables together for about 30 seconds. I reconnected the battery, and attempted to start the truck. It started immediately. 

I played with this for a few more tries. Let the truck idle, when it stalled I disconnected battery cables and touched them together for 30 seconds. The truck started up immediately every time. While the truck was idling, I tried to keep an eye on the modules through my VCX Nano and GDS2 software. Every time I tried to get into the ECM, the truck stalled. After it stalled, I'd get error messages saying "lost communication with module" or "no communication with module." I'm really thinking my ECM is shot.

 

EDIT: Forgot to mention i had an issue with shifting into park tonight. I moved the truck to a different spot in driveway, tried to put it in park, and the dash indicator started flashing "N" and truck rolled back. For some reason even though I had moved the shift selector up to park, the truck still thought it was in neutral. I had to re-engage the shifter and put it back into park.

Edited March 6, 2021 by rugz31

[silveradosid]

have you looked at the freeze frame data to see if there is a specific cause. also being a 2014 i would check the 218 ground connection, was a common problem

[rugz31]

12 hours ago, silveradosid said:

have you looked at the freeze frame data to see if there is a specific cause. also being a 2014 i would check the 218 ground connection, was a common problem

I've tried, but I'm honestly not exactly sure what I'm looking at. My cheap scanner shows the DTC associated with stall is U0101 Lost Communication with TCM. Haven't been able to access it on GDS2 but I'll keep trying.

One of the first times the truck stalled, I ripped the dash out on the side of the road to deal with the 218 ground, but it's possible I didn't get enough insulation out. I'll give that another look tomorrow because my original thought was BCM failure. Since I'm having the shift issue, I think that rules out BCM but it's possible the two issues are unrelated.

[silveradosid]

you want to see the time stamp on when the codes are set. the p0621 code maybe the cause of all of this, i would try and solve it first. https://www.obd-codes.com/p0621

[rugz31]

7 hours ago, silveradosid said:

you want to see the time stamp on when the codes are set. the p0621 code maybe the cause of all of this, i would try and solve it first. https://www.obd-codes.com/p0621

I was wondering about that code as well, a lot of the symptoms line up with what I'm experiencing, but the tech I've been trying to work with from VIA Motors is saying none of the codes are relevant. His thinking is something is causing the shift box to lose signal and causing the shutdown when it doesn't get a response. I've got no idea if he's onto something or if he's completely off, he's been kind of all over the place since I started working with him.

I was able to pull freeze frame data and it shows a new code listed as Failure 1, P2160 Vehicle Speed Sensor 2 Circuit Low Voltage. I have no idea if this is relevant or if this is another symptom I'm wasting time chasing rather than the root cause.

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