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?? None of the fluid reservoir tanks in my 2011 Volt or my 2017 Bolt have a float that I have seen. For sure the battery coolant reservoirs do not.
Thanks Steverino (y) I never looked at the tank all that closely, just going by what they told/sent me. I figured in either case that the switch bypass would fix the issue, whether there was something inside the tank telling the switch (incorrectly) that the level was low OR if it was a bad switch. Please correct me if I am wrong, but as long as the SHVCS warning isn't being displayed, I can just install the bypass and it shouldn't come back? Doug
 

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?? None of the fluid reservoir tanks in my 2011 Volt or my 2017 Bolt have a float that I have seen. For sure the battery coolant reservoirs do not.
Steve, I'm 99% sure the battery coolant reservoir in my 2015 has a float switch at the bottom. I have removed the sensor from the reservoir and bench tested it. It is a simple magnetic switch and can be activated by attaching an ohmmeter and then placing a magnet near the base. The float switch has a float and a magnet at the bottom. The float holds the magnet up until the fluid level gets too low, then the magnet falls to the bottom of the tank, activating the sensor which is mounted just below it. Your 2011 didn't come with the float switch from the factory, but it should have been added by a dealership when it was retrofitted.
 
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Maybe I'm wrong.But I don't see one in the tank. I'm not finding one in parts diagrams either. Could it be a non-replaceable part molded in when the tank was made?
 

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Maybe I'm wrong.But I don't see one in the tank. I'm not finding one in parts diagrams either. Could it be a non-replaceable part molded in when the tank was made?
The only way I could see it would be to drain the tank and use a flashlight. The only service manual I have is for a 2012, so it wouldn't show up there. I'm thinking you're right about the float being non-replaceable and installed when the tank was molded.
 

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OK guys, I guess this is a little bit of a thread hijacked but here goes anyway :)

It took six LONG days for the bypass to get to me in Chandler AZ from Chico CA. I had all the codes reset at the Chevy dealer, then drove the car home on hold in hopes that not using the battery would decrease the odds of the SHVCS warning coming back on. We left the car sitting unplugged until today, I just installed the switch bypass at lunch. The hardest part BY FAR was getting the clip to release so I could pull the cable from the bottom of the reservoir. All the rest was easy ! I haven’t driven the car yet, but no warnings and no CEL when I briefly turned it on after reconnecting the battery (y)

One last question, and the reason this is a bit of a hijack, where is the overflow hose from the battery coolant reservoir supposed to go? In the process of finding a place to Velcro my switch bypass, I discovered that my overflow tube just goes kind of behind the right headlight and hangs there. Is it supposed to be clipped to something or go into a hole somewhere?

Thanks again, thanks especially to the folks who developed and produce the switch bypasses! Doug
 

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I have the SHVCS error currently and the only dealer is 2+ hours drive. I want them to clear the codes and replace the sensor so that the error doesn't return before I get home again to install the defeat. Does this make sense or does the dealer clearing the codes keep the car error free for a while even with the original sensor in place?
Hey Alkers. Mine was diagnosed as having a stuck float in the reservoir, which is $733 at the two dealers I checked. That was a no go for me, so I just had them clear all the codes and drove it home on hold. Now my drive home was probably only 20 minutes or so, but the warning did not come back. I ordered the bypass and let the car sit until today, when I had a chance to get it installed. No CELs or warnings when I briefly turned it on(y)
 

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I ended up making the trip to the dealer and they then told me after a four hour wait that their technician wasn't in that day and I'd have to make another appointment - complete waste of a trip.

In the meantime, my sensor came and I installed it.

I'm just not clear on the last step of the instructions, should I put the sensor back in place underneath the reservoir and then cap it with the connector that the defeat came connected to?

I don't need to do anything with the two wires coming from this connector?

Can I not remove the sensor all together once the defeat is installed?
 

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I ended up making the trip to the dealer and they then told me after a four hour wait that their technician wasn't in that day and I'd have to make another appointment - complete waste of a trip.

In the meantime, my sensor came and I installed it.

I'm just not clear on the last step of the instructions, should I put the sensor back in place underneath the reservoir and then cap it with the connector that the defeat came connected to?

I don't need to do anything with the two wires coming from this connector?

Can I not remove the sensor all together once the defeat is installed?
I should add I've ordered a vx nano so I can reprogramme the modules myself to clear the codes
 

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I'm just not clear on the last step of the instructions, should I put the sensor back in place underneath the reservoir and then cap it with the connector that the defeat came connected to?

I don't need to do anything with the two wires coming from this connector? Can I not remove the sensor all together once the defeat is installed?
The male plug with the wire pigtail is not necessary, it just fills the hole in the sensor to keep junk out of there. I just bent the wires back upon themselves and wrapped with electrical tape before plugging it in to the bottom of the resevoir. Good question on removing the sensor from the bottom of the resevoir... If it doesn't cause a leak or anything (not sure exactly what is going on down there), I don't see why it couldn't be removed. That said, I found getting the wire unplugged pretty frustrating so I won't be messing with mine :eek:

Doug
 

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One last question, and the reason this is a bit of a hijack, where is the overflow hose from the battery coolant reservoir supposed to go? In the process of finding a place to Velcro my switch bypass, I discovered that my overflow tube just goes kind of behind the right headlight and hangs there. Is it supposed to be clipped to something or go into a hole somewhere?
Anyone, anyone? Bueller? My car was babied before I got it, and completely unmolested, so I'm thinking that overflow just dangles behind the right headlight?

Thanks again, Doug
 

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Hi guys, I've got a 2012 with the shvcs message. Took it to the dealership while it was under warranty and they couldn't find a leak. They cleared the codes and it popped back up when the weather changed. I'm out of warranty now.

I've added the WOT sensor and reprogrammed the hybrid system but after some driving it comes back on. I'm guessing the computer systems have enough data to work with by the next time I start the car.

So, how do I check for the wiring harness issue? And is there a solution? Can I replace the harness myself or is this like a pro technician type of thing?

Also, I still have the original 12v battery. I had it checked and they said it was good but needed some charging. Would the 12v cause a shvcs problem?

I've been checking in on this thread for years and it has grown into a beast. I tried searching for an answer but I end up going down the wrong rabbit hole each time.

I'm really counting on a sticky link somewhere that I missed or someone that's been through this already.

Most sincerely
Talan
 

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If your running the 8 year old 12 volt battery it is known to cause weird random issues , like low propulsion ( high voltage battery not loading initially so the car runs in gas mode for 15 minutes ) and various other random issues i will say you are lucky as most of them die around the 4 year mark. ( Mine died in the body shop cause they left car doors open overnight and once it drains completely it's downhill from there. As it died 2 months later getting the 5 year fluid flush service done )

There is no guarantee the 12 volt will fix it but there is a good chance it won't hurt.
 

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If your running the 8 year old 12 volt battery it is known to cause weird random issues , like low propulsion ( high voltage battery not loading initially so the car runs in gas mode for 15 minutes ) and various other random issues i will say you are lucky as most of them die around the 4 year mark. [... snip ...] There is no guarantee the 12 volt will fix it but there is a good chance it won't hurt.
I want to second what Supe said about the age of your 12-volt battery. Eight years is exceptionally long life for that battery! Even if it's not contributing to your present SHVCS woes, it'll certainly be giving you other, equally-irritating problems before long. You're better off replacing it.

( Mine died in the body shop cause they left car doors open overnight and once it drains completely it's downhill from there.
Not so sure about this bit, though. If the doors were left open, after a few minutes the 12V battery protector circuit should have cut off any drain (eg. cabin lights, etc.). Of course, if it's on its last legs to begin with, that might not happen quickly enough to matter.
 

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Hi guys, I've got a 2012 with the shvcs message. Took it to the dealership while it was under warranty and they couldn't find a leak. They cleared the codes and it popped back up when the weather changed. I'm out of warranty now.

I've added the WOT sensor and reprogrammed the hybrid system but after some driving it comes back on.
I can’t tell from your wording whether you had the reprogramming done after installing the WOT sensor. ONCE set, you cannot delete the codes yourself unless you go through the process of subscribing to. the GM system. I cannot tell from your wording whether you had the dealer reinstall the necessary software to permanently clear the code AFTER installing the WOT sensor or not. I do not believe this has anything to do with your 12V battery.
 

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Thanks for the input guys. I replaced battery as suggested and reprogrammed the hybrid module.

I've had the car reprogrammed in 2013. The weather got cold and the light came on. It was just air in the system. It was fine until 2019. The message came back again at the beginning of fall. The dealership checked for leaks, made me buy some coolant from their shop to top off the reservoir and they reprogrammed it. Now it is out of warranty but I used the recent battery software recall notice to get the car reprogrammed again. I purchased the WOT sensor ahead of time to install it for when I got the car back. I purchased the vxdiag and subscription at acdelco as a contingency plan if the light came on before I could install the sensor.

Now, after reprogramming/reinstalling the hybrid software the light comes back on the next day.

The new 12v battery didn't help but I am grateful for the recommendation to replace it.

So it looks like I am down to the wiring being an issue. What about the charging port? Has that been known to cause this problem? I charge outdoors and always get rain and ice in the port. I'm running out of ideas.

We really can't afford the cost to repair the car right now but I can't pass the emission test with the check engine light on.

I can't find much information on the wiring harness.

I think the Volt is such a good car. It is a shame that that this sensor issue has affected so many.

Most sincerely
Talan
 
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