2015 Why did Maintenance Mode start?

3190 Views 13 Replies 10 Participants Last post by canehdian, Jan 2, 2018

Shaft

Discussion Starter · Dec 30, 2017

As it is elsewhere, it is very cold in Toronto this week. The ICE on my 2015 has run every day for long periods of time over the week. I have burned at least 3 liters and gone over 30km with the ICE running.

So why did Maintenance Mode execute this morning? What was the purpose of the 10 minute MM run given all the exercise the ICE had this past week due to ERDTLT?

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canehdian

· #4 · Dec 30, 2017

ERDTT never gets engine to proper operating temp, so EMM is still required if you didn't run the engine "for real" in the last 6 weeks.

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canehdian

· #11 · Jan 1, 2018

wordptom said:
EMM should use only ~0.03 gallons of gas

It will use 3-5x more gas in the winter because of the extreme cold sapping the heat.
Also runs much longer because it's harder to maintain the temp high enough, for long enough.
Many people also would not turn the heater off, which is also drawing heat from the engine, prolonging it further.
And if they don't let it complete to 100%, starts again on next run, etc.
If it triggers and you're already at your destination, best to put it in park, turn off the HVAC and press the pedal down to accelerate the process and let it finish before shutting off the car.

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canehdian

· #14 · Jan 2, 2018

wordptom said:
Thanks for the feedback. Last night the midnight outdoor temperature in my neighborhood in Portland, Oregon, when the New Year arrived was 40 degrees F (4 C), which might indicate I haven’t had much experience with ERDTT in the 5.5+ years I’ve been driving my 2012 Volt, nor with experiencing EMM in that level of cold weather.

I take long vacation drives once a year or so, but hover around 99+% ev with local driving, leaving nearly year-length gaps between long trips (endured my third FMM last October). I find it convenient to avoid adding minuscule gas mile numbers to my records by sitting in the driveway until the EMM has concluded. This also provides me with a rare opportunity to "rev" the engine by stepping on the accelerator.

One oddity I do notice is that the energy usage display usually stops increasing the "Gas Used" quantity about midway or so through the EMM, and eventually concludes some minutes later with no more gas being used. This puzzled me until I read a comment in this forum fairly recently that seemed to indicate this could be proper behavior. The smaller motor is first clutched to and then serves as a starter motor for the gas engine. The EMM is intended to make sure the engine is properly lubricated, so, I suppose, once the fluids attain their proper running temperatures, "engine lubrication maintenance" could be handled just as well by having the motor turn the engine’s internal parts instead of burning additional gas to accomplish the same goal... Is this indeed what happens?

It was -25C (-13F) on NYE this year.
Perhaps that might further what I mention re: cold sapping the heat of the engine that it's trying to keep up

As for the last part, that's correct. I've logged a few with OBD and it only uses fuel for the initial warmup period (which takes a whole lot more when the engine is -25 than when it's +25) then the rest of the period is the electric motor spinning the engine to keep things moving and warm, and fuel use drops to basically 0. You can actually hear the pitch change when this happens, if you're listening carefully.
The net result of EMM is electricity used, not generated (as one would expect if the engine was running itself the entire time).

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