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Discussion Starter #1
I bought my new 2017 CT6 hybrid (plum color) in April 2018 with 69 miles on it. It had lanquished on the dealer lot for a year before I bought it. During my first year of ownership I've only put 2800 miles on it due to being retired. Almost all my daily running around is on battery. I haven't bought gasoline since May 2018.

Anyway, my CT6 finally decided it was time for it's first oil change. Before I scheduled the oil change, it suddenly developed a SERVICE HIGH VOLTAGE CHARGING SYSTEM fault. So I brought it to the dealer.

So the service writer says he's never seen a hybrid come in for service before. In fact, he didn't know Cadillac made a CT6 hybrid. I'm thinking, "Uh oh." The car only needed an oil change, a transmission service bulletin performed, and the fault (battery coolant level sensor?) repaired/cleared. So I didn't bother getting a loaner car.

The CT6 has now been at dealer for two full weeks. Apparently, they were going to do a test drive (I think) and the car died. It wouldn't run on battery and the gas engine wouldn't start. So they pushed it back in the service bay. In checking it out, it appeared that the hybrid battery was dead. I'm pretty sure that when trying to clear the SERVICE HIGH VOLTAGE CHARGING SYSTEM fault, they reloaded some of the software in the car.

Anyway, they installed a replacement 18.4 kwh battery module. Now the car would run, but it still had a fault code. They worked with GM trying to get the fault code cleared. I suspect they reloaded software again, because now the replacement battery appears to be dead. Did you know that the CT6 hybrid gasoline motor can't be started when the HV battery is dead? I imagine the HV battery is used to quick-start the engine on demand.

According to the dealer, GM was making noises about writing new software for the car, so it sounds like a previously unknown software bug may have surfaced. Under California law, the Lemon Law can be applied to a car that accumulates 30+ days at the dealer.

Until this I've been happy with the car. But, if they can't get it fully repaired before 30 days are up, I will seriously consider applying the Lemon Law.
 

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"SERVICE HIGH VOLTAGE CHARGING SYSTEM fault"
(battery coolant level sensor?
There are a lot of threads on this forum about this topic for Volt's.
Some similar issues around this.
I think if done right by the dealer, this should have been fairly minor.
You might give this topic a search.

Do you know if the battery coolant level was low?
 

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Discussion Starter #3
When the fault occurred, I did search and learned it was a coolant sensor reporting low high voltage coolant. I checked the HV coolant reservoir and it was half full (at the tank seam), which is the normal level.

I expected this service to be a quickie, due to it being a known occurrence (among Volts, at least.)

But that was not to be.
 

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On the Volt they later raised the line up closer to the top of tank.
I think this was a decision to have more fluid to increase the margin of error.
 

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GM in their infinite wisdom made all the HV errors latch codes. On top of that in order to clear them you must reflash the entire module. AND then if you didn't solve the problem it comes back and you get to waste even more time doing it again and again.

On top of all THOSE errors, the fatal errors are generic. like the p1e00. which comes up for every error and is also a latch code, sometimes. p1fff is usually the coolant sensor but not always. sometimes the sensor is bad, but it will never ever test bad as its a momentary failure.

and so there you have it. gm engineering at it finest, and the dealers screwing it up over and over because of it.

let it ride, lemon law the car and move on. trust me after they have farked with it enough for 2 batteries and shoving it around the lot, you probably dont want it back from my experience with my 2015 volt.
 

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I bought a 2017 CPO copy (same color, coincidentally) in Sept 2018 with 15k miles on it. The only things wrong with it was the night vision and it hadn't been operated for a long time. It stayed in engine maintenance mode for three tanks of gas and the brakes were very grabby. From the carfax history, it looks like it was a GM exec car for the first year of it's life and went to auction.

Now the brakes are worn back into shape and the hybrid system runs as designed. No real issues so far.

The dealer I bought it from also sold me an ELR prior to this purchase. They have had zero problems fixing and clearing issues that appear. Thankfully, no hybrid system issues or codes on either car.

If I were in your shoes, I would go for the lemon law and buy something else.
 

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Seems like an over reaction to something which should be fairly minor to fix in the first place.
Did they provide a new coolant level sensor?
 

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Discussion Starter #11
I called the dealer today to check on the status of the car. They have received yet another battery pack, but the factory has said to not install it yet, and to contact the factory on Friday, March 29, about a new software download. I gather the factory is reworking the software to fix the problem with working battery packs being "killed" by downloading software. The factory wants them to try this new download with the just-installed new "dead" battery pack before installing a second battery pack into the car. So I'll be in touch with them next week, one way or another.
 

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I hope you follow up with what you find out. This is a pretty interesting thread.
 

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I hope you follow up with what you find out. This is a pretty interesting thread.
Ditto. I own one of these cars.
 

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I hope you follow up with what you find out. This is a pretty interesting thread.
Ditto. I own one of these cars.
 

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Discussion Starter #15
Just an update...

I called the dealer this morning (Friday). Last Friday, the factory said they would release new software for the dealer to try downloading to car. It didn't happen. This week, the factory says the same thing--new software for car to be released today for dealer to download to USB stick and install in car. Dealer service person said to call them this afternoon to see if it happened.

It appears GM is writing fresh software code to fix this problem, which would indicate that my car may the first one with this problem. I guess Cadillac customized the Voltaic software used on the CT6.

In thinking back, to beat traffic and make a left turn into my steep driveway, I made a sharp left turn, accelerated briskly across two lanes, then braked hard to prevent scraping CT6 nose from hitting gutter dip at driveway/sidewalk beginning, then accelerating up steep driveway to get out of way of oncoming traffic. My peripheral vision noticed something flash on the dashboard just as I was starting up the steep driveway. But I quickly parked in garage and exited car.

The CT6 hybrid coolant tank official coolant level is just at the middle seam or so. There is about half a tank of air for the coolant to bounce all around in. Maybe the combination of half-full coolant tank, quick accel, brief hard brake, tires hit dip bottom bouncing nose down then up, then quick accel up steep incline, tripped the coolant level sensor enough for the software to declare a problem. And then the CT6 service procedures couldn't fix it due to CT6 Voltaic software being modified from Volt.

I'm on the fence about trying to lemon law it. I really don't want the hassle. But if the factory offered my purchase money and California Use tax back, I'd take it.
 

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Just an update...

I called the dealer this morning (Friday). Last Friday, the factory said they would release new software for the dealer to try downloading to car. It didn't happen. This week, the factory says the same thing--new software for car to be released today for dealer to download to USB stick and install in car. Dealer service person said to call them this afternoon to see if it happened.

It appears GM is writing fresh software code to fix this problem, which would indicate that my car may the first one with this problem. I guess Cadillac customized the Voltaic software used on the CT6.

In thinking back, to beat traffic and make a left turn into my steep driveway, I made a sharp left turn, accelerated briskly across two lanes, then braked hard to prevent scraping CT6 nose from hitting gutter dip at driveway/sidewalk beginning, then accelerating up steep driveway to get out of way of oncoming traffic. My peripheral vision noticed something flash on the dashboard just as I was starting up the steep driveway. But I quickly parked in garage and exited car.

The CT6 hybrid coolant tank official coolant level is just at the middle seam or so. There is about half a tank of air for the coolant to bounce all around in. Maybe the combination of half-full coolant tank, quick accel, brief hard brake, tires hit dip bottom bouncing nose down then up, then quick accel up steep incline, tripped the coolant level sensor enough for the software to declare a problem. And then the CT6 service procedures couldn't fix it due to CT6 Voltaic software being modified from Volt.

I'm on the fence about trying to lemon law it. I really don't want the hassle. But if the factory offered my purchase money and California Use tax back, I'd take it.
That sequence could have very well triggered a chain of events that leads to the car throwing a code. But why that would disable the car is really questionable. Let us know.


Sent from my iPhone using Tapatalk
 

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Just an update...

I called the dealer this morning (Friday). Last Friday, the factory said they would release new software for the dealer to try downloading to car. It didn't happen. This week, the factory says the same thing--new software for car to be released today for dealer to download to USB stick and install in car. Dealer service person said to call them this afternoon to see if it happened.

It appears GM is writing fresh software code to fix this problem, which would indicate that my car may the first one with this problem. I guess Cadillac customized the Voltaic software used on the CT6.

In thinking back, to beat traffic and make a left turn into my steep driveway, I made a sharp left turn, accelerated briskly across two lanes, then braked hard to prevent scraping CT6 nose from hitting gutter dip at driveway/sidewalk beginning, then accelerating up steep driveway to get out of way of oncoming traffic. My peripheral vision noticed something flash on the dashboard just as I was starting up the steep driveway. But I quickly parked in garage and exited car.

The CT6 hybrid coolant tank official coolant level is just at the middle seam or so. There is about half a tank of air for the coolant to bounce all around in. Maybe the combination of half-full coolant tank, quick accel, brief hard brake, tires hit dip bottom bouncing nose down then up, then quick accel up steep incline, tripped the coolant level sensor enough for the software to declare a problem. And then the CT6 service procedures couldn't fix it due to CT6 Voltaic software being modified from Volt.

I'm on the fence about trying to lemon law it. I really don't want the hassle. But if the factory offered my purchase money and California Use tax back, I'd take it.
The way a lemon law buyback works is after you do all the hoops for arbitration ( do it, sit in the corner and surf on your phone the entire time, its not binding on you and it costs them money like 1500-2500 just to darken the door, just for you to go. do not let them cancel on you or offer to settle the morning of. waste their time and money since they wasted yours. both for the issues and for the BS BBB autoline waste of time pack of lies enshrined into law... ) then it'll go to the lemon law of the AG of your state and they again will try to settle before. pay the $50-100 to have a lawyer review it. make sure it covers everything. this one should be binding and is governed by the state and by law, not any of the earlier ones. Then its a total unwind of the purchase. it's essentially you never bought the car everything is undone and you only pay for your usage. Make sure you stick them for every cost. rental cars, legal fees, consult fees with lawyer whatever. they owe it all. all taxes, add ons, extended warranties, anything you bought especially for the car, a level 2 charger, floor mats, coatings, tint, whatever incidentals, they "buy" off you too. keep lots of docs and receipts. costs ofr any towing or repairs, everything. It's very worth doing in the long run.
 

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Discussion Starter #18 (Edited)
Got my car back today, April 15. It's been at the dealer since March 6. So, 5.5 weeks.

Factory released new software Monday morning, dealer loaded new software, test drove car, and gave car back to me Monday afternoon.

The battery has zero bars. See attached photo.

Hold mode is grayed out when battery empty. See attached photo.

Car is plugged in now and appears to be charging.

Two photos with pertinent part of service order.
 

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Discussion Starter #19 (Edited)
In talking to dealer service desk, here is a basic explanation of what happened.

In trying to clear the fault, the dealer flashed a module. This disabled the car. The hybrid system was giving the appearance of a bad battery pack, and the gasoline engine could not be started.

Factory authorized a replacement battery pack. Replacement battery pack got the car going again, but fault(s) still present. Flashing car again "killed" replacement battery pack (just like it did to original battery pack) disabling car yet again.

Factory said stop flashing module(s) while we (factory) look for software bug.

Five weeks later, factory released new software which appears to have fixed problem.
 

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damn, what a nightmare. both for you and the GM technicians.

so my question is, what is the true state of both battery packs.
 
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