The last few months in New Hampshire we’ve noticed something peculiar happening with our Silverado. Or, well, rather something that’s not happening. The auto stop on our 2019 Chevrolet has auto stopped itself from ever turning on. It took us a while to realize but it turns out we’re not the only ones having this issue.

Let’s backup a second, though. What is this auto stop thing and what does it matter that it isn’t turning on? Auto Stop is a feature GM is including on almost every new vehicle these days that automatically turns off a vehicle’s engine at stop signs, stop lights, or basically anytime you come to a halt long enough the computer thinks it’s more efficient to shut the engine off to save fuel.

Whether or not this is a useful or even effective feature has been debated with ferver on our forums and on our facebook group. But we move on….

We understand that the auto stop feature turns on automatically with every key cycle. We also know that it won’t turn on if the engine is cold or you’re using max air conditioning.

So when our Silverado stopped auto stopping sometime this fall, we just attributed it to something with the HVAC system preventing it from activating. Perhaps the weather getting colder? So, we forgot about it. What’s to miss about your engine randomly shutting off every time you stop?

Then we drove a 2020 Sierra AT4 a few weeks ago and immediately knew our truck was not acting as intended. In our short drive with the AT4 the auto stop worked extensively and at nearly every stop. Pretty much like our truck used to act… until we forgot it wasn’t working like that anymore.

Turns out we were not the only ones. Other owners have reported this issue on our forums as well. So, with this new information in mind we scheduled our Silverado for a trip to the service department at Banks Chevrolet.

What does it matter that auto stop isn’t working? Well, as far as we know the system is used in EPA fuel economy testing (This may not be true, we’re waiting for clarification). So, potentially, there are a large number of full size trucks in the wild not living up to their tested fuel economy (or at least the fuel economy they “could” get…in theory).

When the dealer technician plugged his computer into our Silverado it read back that the auto stop feature was “undefined”, a term you rarely ever want to see in live code. Our awesome tech is currently waiting for guidance from GM on how to move forward with this issue.

Others have suggested that the battery may be to blame. Low voltage, a loose battery terminal and a disconnected ground have all been floated as possible problems.

Our working theory is that the auto stop went kaput after a series of software updates applied to our truck last fall. Maybe the one or more of the uploads or flashes was corrupted. Maybe it’s a software bug that has yet to be discovered. Maybe its some random sensor or electrical fault somewhere down the line.

We’ve reached out to GM for their opinion and will keep you updated with anything we hear from them or the dealership.

UPDATE #1 – We’ve been notified by our dealership that GM believes a faulty battery, which the BCM reads as always being under 75% charged, is the culprit. Apparently the auto stop feature is disabled in “low battery charge” situations.  They will be replacing the battery and we’ll update you on the results.