"Service High Voltage Charging System" Fix (Updated) + VCX Nano Setup Guide (VX Manager, ACDelco TDS, Techline Connect, SPS2)

kdommer67 said:

Any one know a shop that can flash software after I buy the defeat plug? I am in the Toledo/Detroit area.

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You're looking for a shop other than a Chevy dealership to do this for you? The Volts are so rare nowadays, what with it being discontinued for 4 years already, that I wouldn't trust any shop with enough know-how to do this kind of thing for me if I don't even trust a Chevy dealer well enough to do it in the first place, because some Chevy dealers may not even have a trained Volt tech with them. Even if you find a non-dealer shop that can do it for you, not sure how much cheaper it'd be compared to the dealer. If you're looking to save money to fix the SVHCS error, the best way is to DIY. But if you're not comfortable with DIY, then just take it to a dealer.

I have the defeat plug and still got the SVHCS error anyway. So this error is not always caused by a faulty coolant sensor, but can be caused by other things as well. But don't let that discourage you from getting a defeat plug because it still serves its purpose. But I wouldn't install the defeat plug until after I get the dealer to reprogram the software just to keep it simple and not give the dealer a reason to bug you about using a non-sanctioned part in your car.

konimail said:

Trying to troubleshoot my daughter's 2012 Falcon, with SHVS when cold. Car seems to work fine when temps go over 50F, altho it clearly exhibits unbalanced cells, as it will run engine occasionally when battery gets low.
At current state, she's forced to ICE driving it only, and what's worse is - obviously in low population mode which is a safety risk.


Just picked up the VCX nano, and for the life of me I can't get it to work.
Not a computer guru, but am relatively fluent.
1. Would like to get it configured on a W11 laptop. Do I need virtual machine?
2. I have an old VISTA laptop - is it better to set it up there?

I keep getting "no valid lease found" message in GDS2

Any tips would be greatly appreciate.

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The VCX Nano, as a Chinese product, is well known to have Chinese software full of viruses that everyone can see with their own eyes inside their virtual machines without fail. If there hasn't been crystal clear step by step instructions on how to deal with the VCX Nano to get it to work safely by the OP of this thread, I wouldn't even bother touching the VCX Nano with a ten foot pole. Even with crystal clear instructions, hiccups were still encountered along the way because things change, like where the downloads can be found, and versions of the downloads change.

It seems like you're trying to get the VCX Nano to work outside the parameters of the exact instructions imparted by the OP, and for a different debugging purpose than to simply reprogram the HPCM2 and BECM to clear the SHVCS error. I doubt if anybody would be able to or even willing to help you debug and walk through your issues with it remotely on a thread like this because you're not following the imparted instructions 100%, and what you're trying to do is not quite 100% relevant to the thread. So there's not much to reference to because the whole basis for this thread used as reference is the detailed instructions on how to DIY with the HPCM2 and BECM reprogramming.

Volusiano said:

The VCX Nano, as a Chinese product, is well known to have Chinese software full of viruses that everyone can see with their own eyes inside their virtual machines without fail. If there hasn't been crystal clear step by step instructions on how to deal with the VCX Nano to get it to work safely by the OP of this thread, I wouldn't even bother touching the VCX Nano with a ten foot pole.

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Well - thanks for that useless info. I am pretty sure just about everyone is quite aware of the risks involved using Chinese products.

Back to the subject.

I got everything working up to this point:



TechConnect communicates with the car, pulls VIN, and all, but crashes right after .

I can connect and view all diagnostics using the VCX's GDS2. Assuming that one can't reflash and TechConnect is needed to do that ?

( WIN 11 Home, 12GB RAM )

Any input would greatly be appreciated.

PeterK

life_o_reily said:

OK, so this just happened to me (2013) and I have a few observations:

1) I cleared the code with Torque Lite and the SHVCS disappeared, allowing me to charge the car only to to have the fault reappear (noted by many others).

2) Dealer quoted me $320 to reprogram the modules. I immersed myself in the VX nano approach: Ordered the VX nano, subscribed to SPS2, created a virtual machine and loaded the software. Also ordered a new sensor.

3) While waiting for the VX nano, I cleared the fault, removed the sensor from the bottom of the reservoir and checked the resistance, right on 24.7 ohms. I plugged it in to the connector and tied it out of the way. Since then, no faults over the course of 3 days and 3 complete charge cycles.

Next, I think I will reinstall the sensor and see if the code reappears. If it does, then I wonder if the magnet has become dislodged from the float in the reservoir and is constantly triggering the sensor. Has this ever been discussed?

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If I were you, I wouldn't bother with ordering a new coolant sensor, because it may be good for a while, then it'd just go bad again. I took the route of replacing the sensor with the defeat plug to deal with that issue for good.

Sometimes the SHVCS error is due to the coolant sensor, sometimes it's not and it's due to something else. In my case, I had the defeat plug installed way earlier up front, and I still get the SHVCS error a year or two after that. So I know that my SHVCS error was not due to the coolant sensor because it was already bypassed. Nevertheless, my SHVCS error was intermittent in the first summer, I'd clear the codes with the Torque Pro app and it'd be good for several days then threw the codes again. By winter time, the codes went away for good when the temperature cooled down, all the way until next summer when it came back with a vengeance. Then it would constantly throw the codes almost everyday, sometimes twice a day. Then winter came and it didn't go away like the winter before. I kept resetting the codes until I could not longer do that because I had a smog test coming up. That's when I reprogrammed the modules and the SHVCS error went away for good since then.

Anyway, back to your question, I'd suggest you buy and install the defeat plug instead of keep trying to replace the sensor and worry about related things like the magnet dislodged and this and that. I just check my coolant level about once a month instead, which I do anyway with or without the coolant sensor, so it's no big deal for me to defeat the sensor altogether with the defeat plug.

life_o_reily said:

I'm seriously thinking about returning the unopened VXnano, since it seems that clearing with Torque takes care of the fault code, contrary to a lot of what has been posted here. I'm still out the $45 for the SPS2 and the time spent setting up the VM, but that's life. I'd never have gotten to this point without this forum - well worth what I'm out.

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I was living with the Torque Pro and clearing out the fault codes for 2 years, but it's a drag and I wish I had done the reprogramming sooner.

Maybe you didn't catch what I said about why I finally HAD to reprogram -> if you live in the US and in a state where you have to take the Volt in for a smog test every year or couple of years, clearing out the fault codes will also clear out all your emissions monitor data which is required to be available and ready to be read from during the smog inspection. This means that you will fail your smog test. I think you are allowed to have one or 2 or these emission monitors unavailable (1 or 2 depending on the state), and it's not a trivial thing to rebuild/restore the emission monitors data. You'd have to drive through and complete 1 drive cycle to restore all your emission monitors data, and this requires driving the Volt in a certain way through various driving situations.

Of course you can stop charging for a while and rebuild your emission monitors data so you can pass the emission test, then resume clearing the faults with the Torque Pro again until next time. But if you already paid the $45 SPS2 subscription and still have the VCX Nano and already built your VM up, if I were you I'd just finish up the reprogramming just to be done with it for good.

life_o_reily said:

I re-read your post. So, I see that your SHVCS faults continued after you installed the bypass. Were these associated with a P1FFF code or different one? If P1FFF, then it is reappearance of the permanent code that set with the original coolant level sensor failure, since your bypass cannot fail. In other words, am I fooling myself into thinking that my P1FFF won't come back because it hasn't since I moved my sensor a week ago?

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I got the 3 fault codes that most people reported, P0AA6, P1E00 and P1FFF. I installed my defeat plug at the end of 2019 and did not start getting these 3 codes until the summer of 2021, so it couldn't have been due to the coolant level sensor failure because my defeat plug was in place for almost 2 years prior to the faults showing up.

The other thing I said was that by winter of 2021, the faults went away altogether for the whole winter time, and didn't return until the summer of 2022. So definitely it was temperature related, not due to coolant sensor. I suspect that my coolant's resistance level might have changed over time and went out of bound of what the Volt software deems acceptable. The coolant's resistance is probably temperature dependent, so that's why when things cooled down the first winter in 2021, the faults went away until the following summer. But then the faults remained after winter 2022 came, so I'm hypothesizing that my coolant's resistance continued to change such that the cooler temperature of the 2022 winter didn't bring it back in range anymore, although the cooler temperature of 2021 was able to bring it back in range.

I read somewhere that Chevy put an overly tight tolerance on what the coolant resistance should be to begin with, and this has caused the SHVCS fault codes to throw with many Volts. But in their more recent software updates, they loosened up the bounds to a more realistic range. That's why reprogramming the 2 modules would update the software with the newer/looser tolerance values, thereby solving the issue. This is my understanding after reading up on the SHVCS from the GM Volt forum, although I don't remember which thread it is anymore.

So don't think that the coolant level sensor is the only thing that can throw up the SHVCS fault and get fixated on that only. Yes, it's one of the reasons that throws the fault, but not the only reason. So yeah, you can play around with the coolant sensor in your Volt to see if that's the issue or not if you want, since you don't have the pressure of doing the smog test. But if it still gets you nowhere, then do the reprogramming next. But if I were you, I'd actually do it the other way around -> do the reprogramming first, then if the SHVCS fault still throws, then I would investigate the coolant sensor issue next. But it doesn't throw anymore, then you know it's not the coolant sensor.

Volusiano said:

I got the 3 fault codes that most people reported, P0AA6, P1E00 and P1FFF.

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These are the same codes as I saw associated with the SHVCS

Volusiano said:

I suspect that my coolant's resistance level might have changed over time and went out of bound of what the Volt software deems acceptable....
So don't think that the coolant level sensor is the only thing that can throw up the SHVCS fault and get fixated on that only.

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It most certainly is not. I'm no expert, but here is my take: The SHVCS indicates that there was some system failure that might make charging the battery dangerous or impossible. Low coolant level is one such situation, and the code associated with it is P1FFF. P0AA6 and P1EE0 come because of the P1FFF triggering isolation (which is why they always come together). If there is a coolant resistance sensor (Google comes up blank on that one), then a failure would have it's own code, not P1FFF. The fault codes themselves are diagnostic and the SHVCS is a just response to any number of faults associated with high voltage charging. If you had a P1FFF return after clearing codes and installing the defeat plug, then it's because that code was only temporarily cleared and for some mysterious reason it reappears. Does not seem logical, but that does not mean it doesn't happen. Lots of discussion here about the P1FFF being "permanent". From what I have read, you can either reprogram the modules or drive long enough without another failure for it to go away on it's own. For sure, fault code history is part of modern PCM control and helps in distinguishing transient and real sensor failures.
All this crap makes me appreciate my '66 Impala even more.