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Sorry if this has been rehashed already, I promise I read through 5-6 pages at the front end and 4-5 pages at the back end of this thread. I rec'd a letter from GM yesterday that my '14 needs the sw update to increase the warning time before it goes into limp mode (HPCM2 issue). From what I've gathered it's mostly '13's impacted (my '14 was bought in Dec '13). I don't have time or desire to mess with buying and installing the inline harness bypass and messing w/ the fw update on the ACDelco site. Should I have the dealer perform this work? I haven't seen a lot about people getting these letters in the last few weeks and how it's related to this thread or not. Thanks for any advice, all you guys are so much more knowledgeable about this car than me!

Edit: If it helps, the number at the bottom of my letter (simply dated "June 2019") is: N172130462 (18217)
The software update, as the letter implies, will not correct the problem. The WOT sensor substitution will do so.

What the software change does do is extend the time between the sensing of low coolant in the battery cooling system and the reduction of the power, giving you some precious time to pull over out of harms way before power is shut down. The desire of the engineers was to protect the battery. They inadvertently caused potential peril to the occupants of the Volt due to the short timing sequence in the original software.

The problem can occur in all the Gen1 model years, including 2011 and 2012 having had the battery mod performed by the dealer.

If you want to remove any possibility of having an erroneous low power event from occurring, I recommend that you install the WOT sensor. As was explained by WOT (somewhere on this list <grins>), there are other sensors that will protect the battery in the event of coolant loss or low level. The current wisdom is that the additional sensor added to the mod was for political reasons made to insure that the government entities would be satisfied that the problem(?...there are two schools of thought on that) had been sufficiently dealt with and GM could get on with selling the Volts.

The substitution is NOT that hard to do. The instructions are easy to follow. I wrote of my experience in doing so (somewhere on this list <grins>).

EDIT: OK, I looked up my posting. It is #192 dated 4/18/2019
 

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Sorry if this has been covered. After receiving my service notice, I was going to remove the WOT sensor sub so that I could take the car in. Unfortunately, the wiring from the original sensor did not stay tight and it looks as though it dropped down into the fan blade, chopping off the plug.

What is the part number of the original sensor.

Thanks.
 

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Sorry if this has been covered. After receiving my service notice, I was going to remove the WOT sensor sub so that I could take the car in. Unfortunately, the wiring from the original sensor did not stay tight and it looks as though it dropped down into the fan blade, chopping off the plug.

What is the part number of the original sensor.

Thanks.
CCIE in post #309 states:

"The sensor part# is 22922224. Any GM dealer part dept can get it for you next day. Or order it online.Disconnect the battery when you change it.


I replaced mine using that part number, and reprogrammed HPCM2 using a VCX Nano. I also have a WOT sensor on order."

Hope that this helps.
 

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Sorry if this has been covered. After receiving my service notice, I was going to remove the WOT sensor sub so that I could take the car in. Unfortunately, the wiring from the original sensor did not stay tight and it looks as though it dropped down into the fan blade, chopping off the plug.

What is the part number of the original sensor.

Thanks.
I brought mine in for the service, and didn't disconnect the WOT bypass plug. They don't check for that during the reprogramming, and probably never lifted the hood. Nothing was said to me about the sensor or WOT plug.
 

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I brought mine in for the service, and didn't disconnect the WOT bypass plug. They don't check for that during the reprogramming, and probably never lifted the hood. Nothing was said to me about the sensor or WOT plug.
I had the same experience. I had forgotten about the WOT sensor and brought my Volt in for the state inspection and the updated software install. Nothing was said about the sensor. All is good.
 

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Just an update - we are still offering the SHVCS defeater bypass kit at canbustools.com as others have asked recently on these forums. Additionally,we have found better international shipping rates to Europe, 15 USD overseas. If you need to contact us directly please see the e-mail address on our website for the shvcs defeat plug, we have had some e-mail issues with our current provider and now use a g-mail account. Thanks - Brock
 

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Well, I guess it had to happen sooner or later. Got the dreaded "service high voltage charging system" message om my 2012 (80K). The battery coolant tanks are filled to the top of the black sticker. Put a new sensor in and soldered in a new factory connector. I have a cheapo Performance Tool OBDII scanner but I'm unable to clear the DTC (P1E00) and SHVCS. I tried disconnecting the 12v battery and pulling the high voltage plug under the center console for 10 minutes but no go. Is there anything else I missed or will it take a trip ($$$) to the dealer to reset the modules?
 

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Does anybody have a VCX Nano that I can borrow? I figure this will be one of these modules I buy and use once and then it sits around. I realize that I have to purchase my own ACDelco Vehicle Programming subscription for my VIN but figure can save some money with a used VCX. Or does the VCX lock to a VIN as well?
Thanks in advance!
 

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I don't understand why the dealer has to reset it. Can someone explain, can the trouble codes not be reset with a full function Autel type scan tool that can access all modules?

Yes it is plug and play. there are steps, like disconnect the battery, disconnect the old sensor, etc. But it does just plug into the existing harness.

Note: if you already have the error message, then it will not make it go away. The dealer will have to reset it. Then you can install the defeat device.
 

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I don't understand why the dealer has to reset it. Can someone explain, can the trouble codes not be reset with a full function Autel type scan tool that can access all modules?
The GM engineers wanted to protect the battery and made the sensing of low battery coolant into a hard failure requiring the car be brought to a dealer to diagnose and repair. The engineers didn't want batteries failing in the field due to customers ignoring or temporarily fixing low coolant levels without determining why the coolant was low. The battery needs the coolant flowing to stay healthy.
Now, we know that the sensor itself can fail and cause a shutdown to occur. Just replacing the sensor with the WOT sensor after the fact will not resolve the problem. The dealer needs to perform a re-flash with special equipment. It's not something that can be done with an OBD2 scanner. So, it's important to install the WOP sensor before the original one fails.
EDIT: Sorry, I didn't answer your question about the Autel scan tool, specifically. A module has to be re-scanned with factory software. I'm not sure that Autel can supply the specific software for the Volt.
 

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A module has to be re-scanned with factory software. I'm not sure that Autel can supply the specific software for the Volt.
Yes, the firmware in the module has to be completely overwritten in its memory. GM calls it a "calibration" but it's like a flash memory update.
 

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Yes, the firmware in the module has to be completely overwritten in its memory. GM calls it a "calibration" but it's like a flash memory update.
Thanks JuneBug for describing what has to be accomplished. My use of re-scan was incorrect, though I meant what you have written. Bottom line, install the WOT sensor BEFORE the problem arises.
 

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keep in mind that the WOT sensor plug may still connect to a wire harness that was an ADD on by dealer in some of the early Volts and should be tested. (it may even be part or the sensor replacement kit )

MY understanding was that a system input port was repurpose to read the coolent tank sensor as part orthe upgrade ?
 

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keep in mind that the WOT sensor plug may still connect to a wire harness that was an ADD on by dealer in some of the early Volts and should be tested. (it may even be part or the sensor replacement kit )

MY understanding was that a system input port was repurpose to read the coolent tank sensor as part orthe upgrade ?
Good point. From your signature, I see that your 2012 would have been a candidate for the mod that included splicing the wiring, as did my leased 2012 (built November 2011). I never did have the mod installed on my car. So, someone in Ohio bought my car and doesn't have to worry about a failed coolant level sensor, 'cause there ain't one.:p
 

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I am having a difficult time installing the Canbus SHVCS Defeater plug. The directions are not explicit enough for my minimal mechanical ability. What is done with the 2 pigtail wire leads coming from the defeat plug? How exactly is the new sensor plugged into the previous site? I did not yet remove the present sensor because I was not sure about the next step. I was installing a new 12 volt battery, so it would have been an ideal time to put in this plug, but I will disconnect the negative battery terminal when I am confident enough about what to do. Thanks for any help.
 

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I am having a difficult time installing the Canbus SHVCS Defeater plug. The directions are not explicit enough for my minimal mechanical ability. What is done with the 2 pigtail wire leads coming from the defeat plug? How exactly is the new sensor plugged into the previous site? I did not yet remove the present sensor because I was not sure about the next step. I was installing a new 12 volt battery, so it would have been an ideal time to put in this plug, but I will disconnect the negative battery terminal when I am confident enough about what to do. Thanks for any help.
If you remove the old sensor from the bottom of the reservoir, and you're confident of the existing harness, there is no need for the female connector with the 2 leads. See post #385 for an explanation of what two situations might call for usage of that component. Old unit unplugs from harness and new unit plugs in. It's really that simple.
 

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I am having a difficult time installing the Canbus SHVCS Defeater plug. The directions are not explicit enough for my minimal mechanical ability. What is done with the 2 pigtail wire leads coming from the defeat plug? How exactly is the new sensor plugged into the previous site? I did not yet remove the present sensor because I was not sure about the next step. I was installing a new 12 volt battery, so it would have been an ideal time to put in this plug, but I will disconnect the negative battery terminal when I am confident enough about what to do. Thanks for any help.
It's really quite simple. After disconnecting the 12 volt battery, simply unplug the connector from the sensor at the bottom of the tank. Then, insert the defeat plug into that connector you unplugged. The defeat plug will "fool" the computer into thinking it's plugged into the sensor. You can leave the sensor on the bottom of the tank or remove it--it slides right out. Removing it made it much simpler for me to disconnect the plug. My sensor is stored in the center console. Finally, reconnect the 12 volt battery.
 

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So I have the P1E00, P0AA6, and P1FFF codes and SHVCS warning. Battery coolant level is at the bottom of the black label (not top, but pretty far above the seam), so I’m guessing guessing it’s the sensor. I’ve purchased the Canbus SHVCS Defeater plug and the VCX Nano. I’ve read all the instructions and everything seems pretty straight forward. However... the instructions say I need to clear the codes before installing the defeater plug. Wouldn’t they just come right back on if I did it in that order? Wouldn’t it make more sense to first plug in the defeater plug, then clear the codes out?
 

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So I have the P1E00, P0AA6, and P1FFF codes and SHVCS warning. Battery coolant level is at the bottom of the black label (not top, but pretty far above the seam), so I’m guessing guessing it’s the sensor. I’ve purchased the Canbus SHVCS Defeater plug and the VCX Nano. I’ve read all the instructions and everything seems pretty straight forward. However... the instructions say I need to clear the codes before installing the defeater plug. Wouldn’t they just come right back on if I did it in that order? Wouldn’t it make more sense to first plug in the defeater plug, then clear the codes out?
Why not clear the codes first? Then, disconnect the 12V battery, and finally install the bypass plug. Re-connect the battery and you should be good to go. AFAIK the codes would only come back if you were to power up the car and/or drive it. What year is it? The 2011/2012 models were re-wired for the sensor by the dealerships under a recall program. Some dealers didn't do a very good job splicing the wires and the harness gets corrosion which will set the codes. The defeat plug will not help in that situation.
 
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