EV mode not switching on or off

For the last couple of days it seems that the EV button often fails to engage or disengage EV mode, and requires a second push of the button. When I hit the button I always get the single beep and it briefly changes to the Energy screen as expected (unless it denies EV mode outright, but I know how to recognize that), so I know the button itself is working and sends a signal. The display then switches back to Can-view as expected, where I can see the Can-view EV mode indicator (which displays the mode accurately). But in the meantime I've had a short duration of either running the ICE unnecessarily or accelerating on the battery. More frustrating is not knowing when it will behave or not. When it first started I was pushing the button repeatedly as I started second-guessing whether I knew what mode it was in to begin with.

Multiple tests in the driveway last night confirm the behavior: It beeps once and switches screens in all cases (except when denied), it intermittently fails to engage or disengage EV mode with the first button push, it always responds to the second push, Can-view accurately displays the mode, and I always get the 3 beeps when EV is denied.

Any EV switch users ever experienced this? Any theories?

 

Thanks, Evan. To make sure I understand what you're saying, it sounds like you're describing "EV Deny." But this is not EV Deny behavior based on my understanding of EV Deny. I'm not getting the 3 beeps and the "EV Denied" prompt in Can-view (except when it's supposed to deny it -- S1, low SOC, >34 MPH, etc.). I knew about EV Deny before I put the switch in and I have experienced it at predictable times from the get-go. This is new, consistent, and different -- and unlike anything I've seen described on the forums, unless I've just missed it.

 

Forgive me for pestering you, but I'm still trying to understand. Though you don't get the 3-beep EV Deny notice, do you get the single "EV Accept" beep and see the momentary toggling between Can-view and the Energy screen? That's what I'm getting.

And what I'm seeing has become common the last couple of days (and again, non-existent beforehand), and under few of the conditions you describe. Temperatures have been rather moderate (about 70F when I tested it in the driveway), no AC. Probably the only common denominator is the warm ICE.

 

OK, an update: I just came back from running a couple of errands (first trip out today), and it's behaving. It's really odd that with maybe a couple dozen tests in the driveway last night, it "mis-fired" at last half the time. Maybe it's just the Prius' sun, moon, and stars that were all lined up.

Anyway, Evan, thanks for the information and the reassurance. You must tire of newbies' (of which I am one with the EV switch) PC panic attacks, but like any good doc you assess, diagnose, and treat without judging!

 

Just like a worrisome patient, I'm back with the same symptoms, only more pronounced. I'm just about convinced it's abnormal.



There were times during this morning's commute where I'd push the button 5-6 times before EV mode kicked in. Again, one single "EV Accept" beep each time, toggling of the display between Can-view and Energy, and no EV Deny indicators. In addition, something I temporarily overlooked in the earlier discussion is that EV mode also often fails to terminate when the button is pushed. Evan (or others), have you ever seen that?

 

Thanks, Daniel. My first thought was the ECU pin, but I didn't want to dig in there to work on that if there was another more likely cause, or at least one easier to troubleshoot and possibly rule out. The key bounce probably falls into that category, and I hadn't thought about the possibility of a "two-fer" when I push the button. I'm using the home-grown EV button with the Radio Shack switch, so it might be worth it to spend a couple of bucks to replace it. Not much lost if it doesn't fix it. Or, as I think about it, I could de-solder the existing switch and try to replicate the symptoms by just touching the wires together.



Meanwhile, ideas from others are welcome.

 

Thanks, Tim. This is now officially baffling. It worked perfectly on the trip home this evening.

I'll continue on the path of an intermittently bad connection or switch for the time being. I certainly want to believe that rather than a problem instrinsic to the car.

 

<div class='quotetop'>QUOTE(Skwyre7 @ Jun 19 2007, 11:40 AM) [snapback]464679[/snapback]</div>

Will your confidence in me be restored if I tell you it's been OK the last couple of days? No more problems, except possibly once (which could have been me), since Saturday morning's error-filled drive.

 

I'm resurrecting this thread because the problem has resurfaced after lying dormant for several months. Very few recurrences after my last post until recently, but it's back with a vengeance. Now it seems related to ICE temp. I can't plug in the block heater at my new townhouse, so I start there with a cold ICE in the morning. EV "misfires" have been commonplace on some of our colder mornings (20s or 30s) until the ICE gets up to S3/S4 temps. (But then I don't generally need it.) From there it pretty well behaves. But given the cold starting temp, slow speeds, and some good ICE-off gliding opportunities early in my commute, that can take ten minutes or more (once I get the #$%@ switch to finally work!).

When I've started from my fiancee's house, I've had no problem. But there I'm past S2 within a couple of minutes; I can plug the EBH in and I start on a two-lane 45 MPH road where I pretty much have to run in ICE-on conditions. So by the time I'm ready to use it (slow speed glides before I have an opportunity for the S4 idle check), I'm at 70C+.

So all this makes me wonder whether it's related to what amounts to a forced prolongation of S2. Do any of you other EV switch users have a situation where, assuming a properly functioning EV switch, it might take 10-15 minutes before 70C is reached?

I never replaced the switch because the problem seemed to mostly resolve on its own, so I can always do that. But what is the likelihood that a simple pushbutton is prone to temperature-related malfunction? Any more theories or ideas?