Okay, yes, I'm a newbie here, but I have run a few searches and tried to read up about this before posting. I haven't seen anything quite like this. Typically I've read references to a more spuratic/short-lived occurance than what I'm experiencing.

I've had an issue with my 2006 (bought used @ 20k miles, put about 4k miles on it over 4mo; ave 43.2 mpg) and the AutoStop failing to engage.

In general autostop will run fine and engage regularly right off the bat, but every now and then it will go through a period where it just WILL NOT engage -at all -for anywhere from 4 days to a week. Then, just as suddenly as it stopped it will engage again and work pretty consistently for another few weeks. Sometimes the period at which it kicks in would be part way through a trip that it hadn't been engaging, sometimes it's just the "next trip" where it runs from the get-go.

Same driving route.
Same (perceived) behaviors.
Similar environmental conditions.
Outside temp ranging in the 60-80*F zone (not too cold/hot).
35min commute, so car gets plenty of chance to warm up.
No A/C, No defrost used.
Full consistent pressure on brakes (no weakness or let-up).
Battery charged to 4 bars or greater.
Regen/assistive braking working as expected.

No error codes triggered. Car has always had all the routine maintenance that the maintenance minder triggered.

Mentioned it during the last oil change, but no ideas from the techs.

It's the sustained long-lived nature of its failure to engage that concerns me. I kind of 'get' an inconsistent periodic event, but not something like this.


Any others with something similar, or any ideas?

 

Have your service center examine for fault codes in the HVAC system. This is usually the reason that the autostop fails to engage, and HVAC errors will usually not set off the CEL.

 

No fault codes were detected when I was in to the dealership for an oil change two weeks ago and was asking them about it.

 

They normally don't query the HVAC system for faults. During my "adventure" with autostop failure, it took my dealer 2 weeks of poking around the engine and IMA diagnostics with no success until they actually looked at the HVAC subsystem, and found the issue.

 

Is the gear shifter solidly in 'D' ? It doesn't autostop in 'S' and I guess there's an outside chance that the sensor in the gear changer is 'seeing' 'S' rather than 'D'.

Maybe if the gear shifter is a little loose?

I know I'm grasping a little...

 

have you had your breaklight switch recall performed?

Brian

 

I have had this issue as well, but none as severe as the problem you are experiencing. My issues usually occur when it is very hot outside and I have the A/C cranked, auto stop does not engage "occassionally". I live in the south and on those 95+ hot summer days A/C is a must. After some experimenting I did notice that as I approached a stop, if I shut off my A/C, I had no auto stop issues. Not trying to diagnose, just giving you some of my experiences.