[Starfire72]

I tried to jump another GM vehicle the other day , ( gmc terrain )
Didn’t get it going .
After this, it hasent gone into an auto stop , even with everything off , it’s been about a few days now , and I genuinely like it . Especially those long lights, no point in idaling.
Clears the codes. Disconnected the batter for a few seconds , checked fuses, nothing .
Thinking about taking to the dealer, anything else I should try or give it a. Few days? Maybe it needs to “ relearn “ ?

 

[Orange Griswold]

Your battery may now be low enough that the auto start/stop won't engage. Pretty sure these systems need a certain battery level to engage the system. I'd have your battery level checked.

 

[85S10/21TBRS]

I also have a 2021 TB RS 1.3 AWD and suddenly (to my delight) the auto stop has stopped working. Here is South Florida it is an annoyance. Can't stay off during a traffic light complete cycle because the a/c needs to kick back on. Did nothing unusual to cause the non functioning. Just concerned as to why it has crapped out. I will check battery voltage but nothing else seems to be affected.

 

[85S10/21TBRS]

battery with vehicle off 12.3v running at idle 13.3 ... old school me says those numbers are too low....

 

[ZR2LIFE]

battery with vehicle off 12.3v running at idle 13.3 ... old school me says those numbers are too low....

I would agree that's a little low. A fully charged battery should be close to 12.5v and running it should be around 14.5v. One word of caution about newer charging systems is they charge on demand vs old school constant charging where the regulator would only cut off to prevent overcharging. When checking a newer system just be aware that the running voltage at the battery can vary depending on battery demand.

When I had my RS I did notice every once in a while the auto start/stop wouldn't work and I found the cause to be the compressor running even when it was turned off. Any time the compressor runs the auto start/stop is disabled automatically. In my case the compressor would get stuck on even when all HVAC controls were off. It was very random and would do this for a few days at a time before working normally again.

 

[85S10/21TBRS]

I really appreciate the response, ZR2LIFE. I will wait and see if it clears up on its own. In the meantime I booked an
appt with the local Chevy dealer but it is 2 weeks out (first available appt) ...as the hurricane damage and labor
shortage plague this area in SW Florida.

 

[85S10/21TBRS]

Finally got to the dealership ....was told battery was not fully charged..yet alternator is ok. [email protected] pointed out the
running voltage can vary depending on demand. Here is an article from the most recent RockAuto newletter..

Battery Current Sensors

When installing electrical accessories (lights, winches, etc.) on newer vehicles, be careful not to make electrical connections so close to the battery terminals that you inadvertently bypass a Battery Current Sensor. The computer increases or decreases alternator output based on the amount of electrical current it sees being drawn through the Battery Current Sensor. When new electrical connections are made directly to the battery terminals, the current going to the new accessory is unseen by the computer, alternator output is kept low and the battery eventually goes dead.

See the Battery Current Sensor for your specific vehicle under "Electrical" in the RockAuto.com catalog. The repair manual (found under "Literature) or owners manual can also help determine if your vehicle's Battery Current Sensor is on the positive or negative side. Battery current sensors are most commonly part of the negative battery cable circuit. On those vehicles, grounding a new electrical accessory to the body or engine block rather than directly to the negative battery terminal is all it takes to avoid bypassing the Battery Current Sensor.
Typical Battery Current Sensors
Typical Battery Current Sensors
The computer and its Battery Current Sensor also change how to use a multimeter to check alternator output. To maximize fuel economy, the computer may use the Battery Current Sensor signal to keep alternator output as low as possible. That means a multimeter's probes placed on the battery terminals may show less than 13 volts when the engine is idling. That low voltage does not mean the alternator is bad. It may just mean the computer has not increased alternator output because there is not enough current going through the Battery Current Sensor. Turn on the headlights, rear window defroster or some other significant electrical load. The computer will respond by increasing alternator output, and the multimeter will read ~14 volts at the battery terminals.

Tom Taylor,
RockAuto.com