Chevrolet volt battery coolant sensor defeat plug - service high voltage charging system

In case you keep getting the service high voltage system error in your Chevy Volt or Opel/Vauxhall Ampera you may consider installing this coolant sensor defeat plug. This is a description of how I went about installing it myself. The video is not sponsored in any way.

[@Geragers123]

I did exactly what you said and replace the sensor and it work fine I took it to the dealer they want it to charge me $750.00 to replace it save a lot of money thanks for your advice

[@jaybee3165]

it worked! great call erik. just a side note: find something to pull up on the back (near the hatch, not the seat) part of the cover to get at the battery hatch). undo the negative terminal, swap the plug, reconnect the battery AND THEN you have to connect an obd scanner & clear the codes in order for it to work. but- it did work.

[@jordannigesiewnarine]

what kind of OBD scanner did you use? I just did your suggusted steps but unfortunately when i try and clear with my OBD, it the SHVCS error comes right back on

[@jaybee3165]

@@jordannigesiewnarine did you disconnect the 12v. battery FIRST?

[@jordannigesiewnarine]

@@jaybee3165 yeah i followed your steps, first disconnected the negative terminal for the 12v battery in the back, switched the coolant sensor with the defeat plug, reconnected the battery, turned the car on and tried to clear with my obd and the shvcs error was still there unfortunately

[@jaybee3165]

@@jordannigesiewnarine I borrowed my obd from a corp. that maintains a fleet of vehicles... pretty nice scanner. beyond that? you may have to take it to a mechanic that's really good with vehicle electronics- Asian mechanics ROCK.

[@jordannigesiewnarine]

@@jaybee3165 I see. I went to my local gm dealer and had them flash the HPCM2, and now the check engine light is gone and i am able to charge the vehicle!

[@hermanvonsprudelwasser]

ik ga er mee aan de gang. tot nu toe gebruikte ik een obd2 meter en wiste elke keer de foutmelding.

[@Cucui_6]

your video and the instruction that came with the defect plug is to disconnect the negative side of the battery terminal. does that matter if I disconnected the positive side??? I ask, because I got a P1E00 code the following morning after I did this modification. So I just deleted this with my small Autel reader. Oh, P0AA6 and P1FFF are both in my permanent section of the OBD. A mechanic buddy told me those codes don't come back after a few driving cycles, the permanent section will be erased. But I still wonder if I should go to the Chevy dealership to get the permanent P1FFF and P0AA6 erased?

[@dougmcclelland6139]

As an Electrical engineer of 40 YRS. I can not see the logic in removing the negative. Terminal. I have always taken off the positive terminal. Some think you will have less chances of a spark. Naaah just not so that is just BS.

[@senilssonpn]

Hi, If i will just use a resistor to test it. Do you know the resistance, thanks, Peter (Sweden)

[@linzeng6523]

Read it some where the resistor is 24 k. Give it a try if you want and then share the results.

[@jeffellermeyer4517]

Not successful pulling the plug. I want to cut the wires and solder the appropriate resistor. But WHAT IS THE APPROPRIATE RESISTOR?

[@Uomarfr]

Where from did you buy the plug?

[@melaniemcconnell9963]

Hey, sorry if I am missing something but I do not understand what to do with the male pigtail with those two wires that came with the defeat plug. I see Eric holding them up at the 2min 50 sec mark near end of the video and saying they should be attached to The original to avoid corrosion. I just don’t know if that means I plug it back into the original “T” cap And slip that back into its location on the bottom of the reservoir. If so, what do I then do with the two wires from the pigtail. Again, I apologize if I am missing something obvious

[@crackers819903]

i'm wondering the same thing...it can't be a good idea to have two random wires just hanging there, right?

[@spin_kick]

@@crackers819903 This is my question too. I got this sensor and you can see he runs the wire outside of pictures of the plug. I figured it was to prevent other people from figuring out what resistor is used, but could it be this plug needs NO resistance other than what the plug provides with these empty strips of wire?

[@jeffellermeyer4517]

Exactly my question. Any updates on the dangling wires?

[@derrincalk9579]

Also wondering what happens with the bare wires

[@spin_kick]

Question, I ordered the same one and the male plug seems to just run two wires away from itself. Is there supposed to be a resister soldered onto it? From what I can see in your video, I don't see anything on yours as well.

[@spin_kick]

I think I answered my own question. The female plug contains the resistor, the male plug is just a dummy plug that goes nowhere.

[@tompeck7940]

On my 2013 Volt I have replaced the coolant sensor and now installed the defeat/byplass plug. In both cases the SHVC code keeps coming back although I can reset it with a cheap scan tool, which still allows the car to charge but its a hassle to continue to clear the code constantly. Now that I have replaced the sensor and tried the defeat plug I am thinking there might be another problem that is casuing the code to reappear, but I am not sure what that could be. Any helpful ideas appreciated.

[@danwat1234]

My Volt gets the Service High Voltage Charging System error because of 'loss of isolation' code, and in addition the fluid level code when the level is indeed low. Both disable charging until you clear it with a cheap dongle

[@jeffellermeyer4517]

My SHVCS message appeared at 75mph climbing Donner Pass in the Sierras. This was a year ago. I am assuming it is related to the coolant sensor being faulty even though fluid level was good. Now I am wondering if it could be a battery coolant pump that was stressed out on my drive up the mountain. I don’t live near a dealer and would like to find a tech to help me clear the message. BTW I did buy the defeater plug and was under the impression that the message had to be cleared before installation of such.

[@FORGIVENANDLOVE]

When your car explode

[@jermainonye1661]

Did you find an answer to this? I believe i may be in the same boat. I repleased the sensor itself, but error code keeps coming back. If the sensor isnt the issue what else could be causing this code?

[@shawnrussell5138]

The two wires dont do anything is my understanding, its just a dust cover from where u disconnected from coolant tank

[@djpatrick9853]

Hello ,what is the value of the resistance?

[@Ingineerix]

24k worked for me

[@hubamarosi6476]

practically its a short circuit. a I right? @@Ingineerix

[@Ingineerix]

@@hubamarosi6476 No, it's a 24k resistor that worked for me. A short will cause a fault.

[@wilhelm-thomasmicu1690]

Where can I get it in Europe?

[@barrymoney1946]

How do I order one of these please

[@Reaganbites]

Why not replace the sensor?

[@spin_kick]

Likely your vehicle has many miles on it and is out of warranty. I have seen quotes to replace and troubleshoot in the area of $750.00 dollars

[@danwat1234]

Perhaps because the radiator is leaking and you still want to charge

[@santinoblack1]

I tried and it worked for 3 days then same code came up Service High Voltage System😖

[@danwat1234]

Could be a loss-of-isolation code instead. You can just clear that with a dongle and an app every time u want 2 charge

[@cyruz2005]

Nope try the resistor and didn't work light still comes on.

[@edgarhuiltron2184]

Not a fix

[@edmiller6227]

This is REDICULOIUS !!! So to bypass the sensor is $40 plus shipping & tax and you now have to manually check the coolant every so often (STUPID). To replace the sensor is $20 plus tax and shipping AND LESS WORK. Why would you ??? Sensor part gm#22922224

[@crackers819903]

because when the sensor inevitably fails again, you have to take it back to the dealer again and pay more $$$ to get them to clear the code again.

[@davebarbieri1380]

​@@crackers819903 No you don't. The sensor is very easy to replace. Then you just clear it with your scan tool, or take it to Auto Zone and they'll clear it. A new sensor is the way to go.

[@N01_]

@@davebarbieri1380No the codes that the faulty sensor trips are “permanent” codes. You can clear them with a scan tool but it will only get rid of them temporarily. To permanently clear the codes you need to re-flash the Hpcm2 and Becm modules.

[@makermarc3942]

Don't bypass your sensor! The sensor is for protection of your safety, but also protection against damaging your vehicle.

[@spin_kick]

There are other sensors that are designed better

[@n9wox]

SHVS trouble code will still trip if there's a loss of isolation in the battery.

[@NevEP]

And the sensor is only $15 from a Chevy Dealer. It's cheaper than the bypass.

[@YP3CA]

Isn't that kinda like placing black tape over a "Check Engine" light? Why not simply fix the problem instead of putting a band aid that may come back later and bite you in the ass?!

[@WoodburyMan]

The problem is the sensor itself is a faulty design. If the Coolant level is fine, the sensor randomly trips, throwing a code in the car and disabling electric charging until you can get to a dealer and pay $100 to clear the code, even if there is no problem. There's no fix from GM for the faulty sensor.. even brand new sensors do this. Bad designs.

[@Foxxie55]

@@WoodburyMan Yep, I just replaced the wife's 2012 Volt sensor and told her to drive it a few days to see if it stayed clear.. It did for about 2-3 weeks then her engine light came back on.. Every time a light comes on, she quit driving it.. LOL.. I told her if the car charges and runs just keep driving until it completely quits. No actual codes showing anything wrong other than the generic code that thinks that there is a problem, other than that the car works fine.. I grew up back in the 1950s when baling wire and lots of tape fixed things..

[@starbuck1966ncc]

This is a very bad idea, the High Voltage Battery Coolant level is extremely Important, best case is to overheat the battery and degrade the battery, worst case is a lithium Fire!!! Neither are Good!!

[@WoodburyMan]

This is just a Coolant Level sensor. There is a separate Coolant Temperature sensor that is still active and working. Coolant would overheat if it was low and still enact safeties. Likewise it's very easy to check coolant levels at regular intervals and recommended if you do this. This is to fix a defective design from GM. The Coolant Level sensor is faulty and triggers randomly, and once triggered the code cannot be cleared even with a at home OBII code checker and requires a dealer visit and $100+ to fix even if nothing is wrong.

[@AZsmoothrider]

GUYS GUYS GUYS! Just replace the frigging sensor!!! It's $13.00!!!! WHY DEFEAT the sensor? YOU WILL FRY a $12,000 battery pack and maybe burn your car or house down, for what? a $13 part? DUMB.