After dealer service, RPMs running high!

First timer here, thank you for reading.

In January I brought my 2019 Chevy Cruze (50k miles) to the dealer for a state inspection and left with an oil change, new tires, and suggested BG GDI Induction, Transmission Flush, and Brake Fluid exchange.

Immediately upon next using the vehicle, I noticed something new: During my morning commute, I noticed when reaching highway speeds (70 mph) the RPMs would get stuck at 3 and not shift back down to 2 or 2.5 as usual. The car would sound and feel like it was working extra hard and this would continue until exiting the highway back to slow speeds or coming upon traffic - a daily occurrence - forcing me to slow and/or stop.

I brought it back to the dealer who supplied me with Bulletin #18-NA-035 - see here: https://www.tsbsearch.com/Chevrolet/18-NA-035

The bulletin states “some customers may comment that the transmission will not shift into overdrive range during cold ambient temperatures. This condition may be caused by the engine control system detecting conditions that indicate the freezing of moisture in the charge air cooler. When the control system detects the above conditions and the ambient temperature is either below 14 degrees F or slightly above 14 degrees F with high moisture, but not frozen, it takes the following actions: Requests a lower gear than normal (higher RPMs).

Yes, the mornings have been “cold” as in Virginia winter, but not 14 degrees cold. And true, it does not occur in the afternoon when its warmer. But here is my concern:

  • Bulletin says ~14 degrees F, but it has occurred anywhere from 19F to 35F outdoor temps.

  • Its not just at 70mph. I have noticed it stuck at 2+rpm when going 45-50mph with no downshifting. It “Settles” if I push highway speeds to 80mph, but if I dip back into 70mph range the problem returns.

  • Finally, this vehicle has done the same morning commute for 4 previous winters without issue. This is a new occurrence starting directly after my recent service.

This all seems outside of the scope of the bulletin. What suggestions can I return to the dealer with? Could anything be amiss from the fluid exchanges or induction? Could a sensor be misbehaving somewhere?

Thank you for reading.

The computer won’t allow the transmission to lock up the torque converter until the coolant reaches a certain temperature.

This is done so the engine heats up faster thereby reducing emissions.

So, you may want them to look at the signal from the coolant temp sensor to the computer.

Tester

1 Like

Were those procedures actually done? Or are those something that were recommended, but you turned them down? If the only procedures performed at the shop were the tire work & changing the engine oil (& presumably the oil filter), the symptoms are probably not related, just a coincidence. To get to the bottom of it, your shop will probably have to monitor the inputs to the gear selection and torque-converter lock-up algorithm. A pragmatic solution might be to just live w/it for now, warmer weather is soon returning. Sorry you are having this conundrum, Mr smoozer in a cruizer … :wink:

Something simple - might they have knocked off or failed to reconnect a vacuum hose during all their flushing and exchanging?

1 Like

All of those services were done.

Then the symptoms might be related to the trans flush procedure. The problem is, that’s going to be hard to know with any certainty. What are the dealership’s recommendations for the trans-flush interval? 50 K seems a little longer than I’d expect …

2 Likes

I’m not familiar with the set up on this car, so IDK if it’s easy enough to check the transmission fluid level. But I would start there. As well as looking into the coolant temp readings, as noted above.

1 Like

You might think it is a high idle issue from title but seems to be a trans issue due to coolant temp and/or trans not going into OD. Would be nice to see coolant temp during warmup. You might think motor would be at operating temp after 15 min.

1 Like

Maybe you have seen this. It sounds like other have had the same experience based on comments here:

https://www.cruzetalk.com/threads/2019-cruze-doesnt-shift-into-6-gear-overdrive-in-cold-weather.246020/

Interestingly, the TSB (dated 2019, same TSB # 18-NA-035) posted on that thread states that it can happen when ambient temperature is a little above or below 32F.

1 Like

Maybe the transmission flush messed up the transmission and now it won’t go in to 6th or even 5th anymore?

Otherwise I would check that the engine is properly warming up and there are no codes as others have suggested.

Yes I have seen that - thank you! It’s an older version of the bulletin they provided to me. The newest version says 14 degrees not 32. And somehow I drove the same commute in 4 previous winters without issue, yet suddenly directly after the service it happened consistently.

One would think! One day last week it went on for about 45 minutes despite being well above 30 degrees.