Entering Stage 4 - you actually don't need to be fully stopped.

Wth, it's the SAME ARTICLE.
.
_H*

 

Having looked through the service manuals in response to other questions, I'm speculating that it won't go into S4 until it's confirmed that the Mass Airflow Meter is correctly in calibration. The conditions for the monitor run are as follows:

- Throttle fully closed
- Coolant temperature is over 70 Celsius (158 Fahrenheit)
- Engine speed less than 900 rpm

The monitor runs for 10 seconds. If the output of the air flow meter remains over 2.2V it flags DTC P0101. This appears to be the only DTC monitor that runs under these conditions.

Further speculation: if it can't yet trust the MAF, it doesn't want to stop the engine in case it won't start again with a fuel mixture calculated by the MAF, once it's running under closed-loop control (70 Celsius). That would suggest there's a bug somewhere, it shouldn't be stopping the engine between 34mph and 42mph or probably even fuel-cut above 42mph. I don't think it's a coincidence that the engine stop speed range is between the EV mode limit (in the US; we have a 29mph limit here) and the forced engine start speed.

Sorry, I'm prone to wild flights of speculation. Sometimes, when debugging software, it can lead to a root cause more quickly. Sometimes it throws me off a simpler trail.

My route to and from work is quite free-flowing and high-speed, only urban at either end; on the way home from work I won't be restricted to below 34mph until I reach Sonning (20mph limit) and will normally only have the engine shutdown on reaching a set of traffic lights there, and waiting for ten seconds. By this stage, I've done about 12 of my 16 miles. I'll have to try an earlier stop once up to temperature, to see if it makes any difference.

 

..and also in response to Mick Dimmick...

I've also been suspicious that there is a difference between the North American and the European/Australasian models, but haven't as yet got confirmation. If so, then we need to be careful to avoid comparisons might cause confusion.

As Patsparks has experienced, I can also get ICE shutdown just minutes after a cold start while still under 29 mph - I think this is actually S2 behaviour for a non-North American model, not S4.

Here is a picture about three minutes into my morning commute showing a low speed ICE-off glide:
S2 ICE-off Glide.jpg
IGN = 5; RPM = 0
57C (134F) water temp; 24 mph, no arrows glide on MFD.
ICE also remains off when stationary (while engine temps between 40-70C, e.g. about 104-158F).

I'd be interested to hear if any North American models can do this...?

 

With that water temp, that is indeed still within the temperature range of S2 on the N.A. models, where the ICE will cut off only when the the car is stopped (unless forced off with an EV switch).

 

Thanks jim, efusco. I learn something new here every day! :-D

 

Thanks for this helpful post. I hadn't reviewed the prius stages before. Knowing this, I am now full aware of when I'm inducing stage 4.

Out of curiosity, if I'm going about a normal drive and do not have a chance to induce stage 4, does the car never enter this stage automatically after certain temperature thresholds have been met? That's how I've read the info contained in this thread but would like to be sure.

Also, no one ever answered the question as to whether or not inducing stage 4 is useful before entering highway speed. I think this is a relevant question but maybe it's because I'm a novice with knowledge concerning the various stages. Any offers of a reply?

 

That is correct. I've driven on the highway for hours without it getting out of stage 3.

If you don't have an opportunity for a full stop before hitting the highway, I probably wouldn't make one just to induce the idle check. There's no harm in it except burning a tiny bit of fuel, but in most cases there's nothing to be gained. An exception might be if you know that upon your exit you'll transition immediately to sub-34 MPH conditions (where the ICE is in S3A and therefore won't shut down) without an opportunity to stop first

 

Great. Thanks. My weekly normal commute is comprised of mainly pulse and glide so this new info should be quite useful.

It's curious to me why the car wasn't designed to automatically enter this stage when certain conditions are met.