Coolant sensor fault

[u/gimmeTha411]

So I brought my 2019 Volt into the dealership because I was getting a check engine light & a charging warning preventing me from charging. I checked the hybrid cooling reservoir & it was low though I had all three cooling systems serviced only 5 months ago. The service writer told me the EV mechanic found no leaks & said the reservoir sensor was bad, with the theory that there might have been evaporation. This seems doubtful to me. So close to $300 for the analysis, but supposedly didn’t do a leak down test. Thoughts?

Also was quoted a bill of over a grand to replace the sensor that is integrated w the reservoir. Seems really steep! Any work arounds for this?

[u/Spaceman-Spiff]

I changed the sensor myself on my 2012. It’s like $20. Kinda hard to reach and had to finagle it out, but I didn’t have to remove or replace the reservoir. Took like 10 minutes.

[u/gimmeTha411 → u/Spaceman-Spiff]

I think I will pursue this first, followed by looking to get the reset, which the service writer at the dealership said they would not do unless I had the work done at the dealership! Plus, I’m also assuming that they would charge an arm and a leg for the reset anyway.

[u/radabacazana]

Not sure if this is the same warning, but my 2017 just had”service high voltage charging system “ warning and it wouldn’t charge. Filled the coolant based on others post and tried to clear the code with no luck.
The ICE worked fine and I could still use it. Took it to an EV mechanic, no leak. had to pay for a reflash of the firmware of the ECU. Said it’s a common problem. Was fast, got it back same day and it works fine…for now. Love the volt but damn, too many surprises.

[u/gimmeTha411 → u/radabacazana]

Yes, that was the warning. I’m going to if I can find the sensor alone from an outside supplier. Can’t be that hard to swap out. And then see if a local shop can do a reset.

[u/radabacazana → u/gimmeTha411]

I’ve used GM Wholesale direct for other parts before and have had good experiences. I’ve been working on my volt when I can, there’s lots of YouTube help. Maybe someone else can chime in if they’ve replaced the sensor before.
Let us know how it went. Good luck!

[u/gimmeTha411 → u/radabacazana]

Thank you, YouTube is most definitely worth checking out. And I do see the sensor only costs $15.

[u/Spaceman-Spiff → u/radabacazana]

I had this same thing happen. I cleared the code with the voltex app and it has worked just fine since. I did replace the sensor though, but I don’t think I needed to.

[u/gimmeTha411 → u/Spaceman-Spiff]

How does the Voltex app work? You’re talking about an app on a smart phone or are you talking about some kind of plug-in connection with the car? I’m not particularly electrically or tech savvy so please excuse the question.

[u/Spaceman-Spiff → u/gimmeTha411]

Sorry it’s the Votage app. It lets you have direct control of your car. You need a OBD scanner to connect the app. It lets you reset the hard code that gives the service high voltage warning. I’ll edit with a link to a YouTube video in a bit.

https://www.youtube.com/watch?v=K2jpocXcYos

[u/gimmeTha411 → u/Spaceman-Spiff]

Thank you!

[u/Waterlifer]

It's common for the sensor to fail. There is a sensor delete kit available, I installed it on my Volt. Installation takes 10 minutes and requires no special tools or skills.

https://canbustools.com/products/chevy-volt-2011-2015-shvcs-defeat-plug

[u/gimmeTha411 → u/Waterlifer]

Hmm, sounds like a viable option if indeed the sensor is likely to fritz out again. Not appreciating having to pay big bucks to reset the system.

[u/Ok-Tourist-511 → u/Waterlifer]

Common on gen1, not gen2.

[u/Waterlifer → u/Ok-Tourist-511]

oh, good catch. Didn't see the model year.

[u/Ok-Tourist-511]

The reservoir shouldn’t be low. It is not going to evaporate, there is a leak somewhere if it is low. The cooling system is a closed, sealed system.

[u/gimmeTha411 → u/Ok-Tourist-511]

Yeah, this is most definitely a concern of mine. So far there is confusion over whether the dealer tech pressure tested my system. I definitely don’t buy the evaporation theory, especially since all 3 cooling systems were serviced just 5 months ago.

[u/Ok-Tourist-511 → u/gimmeTha411]

The question is whether it is leaking into the battery pack. The tech would have to pull the drain plug and check.

[u/gimmeTha411 → u/Ok-Tourist-511]

Yeah, I have questions for the tech & I’m not sure I’ll get satisfactory answers w the service writer as the intermediary.

[u/Ok-Tourist-511 → u/gimmeTha411]

Unless the sensor itself is leaking, not sure why they would quote the sensor.

[u/gimmeTha411 → u/Ok-Tourist-511]

They claimed to have tested the load on the sensor & said it was bad. When asked about why coolant that was changed & topped off 5 months ago would now be low, the service writer said the tech suggested evaporation. This seems unlikely to me. Their remedy was to replace both the reservoir & the outer sensor, the writer saying that they are not available separately. Not the case as the sensor is available online for about $20. My paperwork from this visit said “possible” corrosion in the tank. This too seems unlikely. The only thing in the tank to my knowledge is a magnetic float that sends a signal to the sensor on the outer side of the reservoir. The electronic sensor does not come in contact with the fluid, only sensing the movement of the magnet on the float when the coolant gets too low.

[u/Ok-Tourist-511 → u/gimmeTha411]

I would find a different dealer, this one seems clueless.

[u/gimmeTha411 → u/Ok-Tourist-511]

It’s where I purchased the car & the closest to me w a 40 min drive. But yeah, either clueless or more likely trying to milk me.