Engine start with shifter in "P"

This behavior was documented at the yahoo group. Here is the link.

<http://groups.yahoo.com/group/toyota-prius/message/13289>

*** Excerpt
we use a learning value for idle speed control.
During D, the first priority is given to stopping the engine to
maximize efficiency. If on the shift to P, the system isn't happy
with its learned ISC value, it may run the engine briefly to update
the value.
*** End excerpt

I guess they are trying to say that if the car was not happy with its idle speed control (ISC) settings it may turn itself on when switching to park so it can update its computers. When this happens you can think of it as the Prius taking a little time to give itself a mini tune up. I notice this happens maybe half the time I put my Prius into P.

Note: There is no harm in turning the car off before it completes updating the ISC. I believe it will just continue to use the "old" ISC values the next time you drive the car.

Ed

Matt Malkin said:

I am still in love with my Prius after less than a week and about 120 miles. Nearly every time I come to a stop at my destination, the gas engine will start immediately after I put the transmission selector in "P." It runs for about 15 seconds and then turns off. Any guesses about why this happens?

Click to expand...

From the toyota-prius yahoogroup FAQ:
http://autos.groups.yahoo.com/group/toy ... sage/13289

(you can also see the original thread on the toyotaprius yahoogroup (former yahooclub) starting here: http://autos.groups.yahoo.com/group/toy ... ssage/6573 )


From: "Sam Williams" <[email protected]>
Date: Thu Jun 14, 2001 7:09 pm
Subject: Why does the ICE run SOMETIMES when in "P"





I asked "ee_of_ee" (Toyota big poo-bah Exec. Eng. for Environmental
Eng. or something like that) on the "clubs" site. Not a simple
answer, but a helpful one:

[Here's the question I asked:]

Dear Dave:
When we are in "stealth" mode, stop the car, and shift into "P",
sometimes the ICE starts up, and sometimes it doesn't. It's very
annoying when it starts up, because when we shift into "P" we intend
to shut the car off. To have the ICE start up just prior to shutting
off the car is disconcerting. Are we supposed to let the ICE "idle"
until it shuts off before shutting off the car? And why does it do it
SOME of the time, and not others?

We've elucidated many mysteries of the Prius, but this one has
escaped explanation. Please help.

Thanks,
Sam, et al



[Dave's answer]:

Sam, et al.

My contacts in Japan offer the following two possible scenarios:

* In D and P two different values are used for engine on strategy. In
D we use 10 kW load (sum of road load, acceleration and battery
need). In P a much lower value is used (to recover SOC). If the
battery need component is the major element of the total load
requirement, then the syustem may start to charge the battery when
you shift into P.

* Second scenario, we use a learning value for idle speed control.
During D, the first priority is given to stopping the engine to
maximize efficiency. If on the shift to P, the system isn't happy
with its learned ISC value, it may run the engine briefly to update
the value.

Hope this answers your question.

Dave


[Alan (n57er) quickly responds with this question:]

This is extremely helpful, Dave, however the question remains: Is it
a problem under either scenario to turn the car off if/while the
engine is running after shifting into park? Should the engine be
allowed to run, howeever briefly or long, until it shuts itself off?
Thanks for the further clarification.
Alan


[Dave comes back with this]

Sorry I left on open issue. Shut down at your convenience. The system
is doing housekeeping and if shut down will just do it at the next
chance.

Dave