[Richard E]

I had an odd thing happen the other day. I was stopped in a parking lot waiting for some friends to get food, with the Acc on for 15 min or so. When I tried to open the tailgate it wouldn’t open.
Trying to start the van I got a “Hybrid System Unavailable” message and a Parking Brake warning and it wouldn’t start.
I tried a few times but nada.

I shut it off, waited 10 min while googling a solution, then it started fine. Drove fine 2 hours home after that, and started fine at gas stop.

I may have borked it with some combination of starting from ACC, or maybe I ran the 12v battery down waiting? I didn’t get a message about that though. Does the 12v recharge from the HV battery if you shut it all off?

(I did see in the manual that you can force a start from ACC by holding the brake down and holding the start button for 15 seconds)

Anybody else have this issue? Is it just a matter of waiting a few min with everything off, or is there a problem for the dealer to fix?
.
Thanks.

 

[esk]

If the engine isn't "READY" then the vehicle is running on your 12v battery exclusively.
The traction battery only turns on when the engine is "READY" so it can be powered and recharged by the ICE.
If you're sitting in ACC mode in ANY vehicle, you're asking for trouble as nothing is charging the 12v.

 

[fotomoto]

If the 12v battery voltage is low enough, it won't have enough power to open the high voltage hybrid battery contact relays to let it (hybrid system) come online. Since 12v batteries in hybrids don't have to "crank start" the engine like in a traditional car, they have smaller capacities and are much easier to run down the voltage/charge.

TIP: avoid ACC mode as much as possible and leave the car in ON instead. Also, get a small LiOn battery bank/charger.

 

[Velox003]

Same thing happened to me a while back while I had the car on ACC and listening to the radio. My car actually died and I had to jump start it. Sounds like you drained the 12v battery but had just enough juice to start it. As fotomoto said do not leave it in ACC move and just leave the car on. The engine will cycle from idle to off and maintain the hybrid battery as needed. This will also prevent the 12v from draining. You may get a check engine code later.

 

[Richard E]

Thanks all. I’m surprised that 15 min on ACC would drain the 12v battery without seat heaters etc. on, but will avoid it in future. I suppose the ventilation system may have been set on heat/defog while we were driving, but surely it won’t run the AC for defrost while on ACC?

 

[pamhar]

Thanks all. I’m surprised that 15 min on ACC would drain the 12v battery without seat heaters etc. on, but will avoid it in future. I suppose the ventilation system may have been set on heat/defog while we were driving, but surely it won’t run the AC for defrost while on ACC?

Have read several comments on this forum where just 15 minutes drains battery to where van won't start. Often there is enough battery to start like 10 minutes later else a call and trip to dealership warranted.

Guess rules out drive in movies unless keep van on, if allowed.

 

[Velox003]

Check out the battery in the back, its almost the same size of a motorcycle battery. I'm hoping it can be upgraded to a standard size, but so far I have not heard anyone doing so. I'll look into it when the time comes, but I don't feel like spending money on something that works.

 

[20swrt]

I would buy one of these in a year or two. Nice to have handy just in case my 12v battery decides to loose voltage for whatever reason.

Top 10 Portable Jump Starters 2022 (buyersguide.org)

 

[Sienna9816]

I had an odd thing happen the other day. I was stopped in a parking lot waiting for some friends to get food, with the Acc on for 15 min or so. When I tried to open the tailgate it wouldn’t open.
Trying to start the van I got a “Hybrid System Unavailable” message and a Parking Brake warning and it wouldn’t start.
I tried a few times but nada.

I shut it off, waited 10 min while googling a solution, then it started fine. Drove fine 2 hours home after that, and started fine at gas stop.

I may have borked it with some combination of starting from ACC, or maybe I ran the 12v battery down waiting? I didn’t get a message about that though. Does the 12v recharge from the HV battery if you shut it all off?

(I did see in the manual that you can force a start from ACC by holding the brake down and holding the start button for 15 seconds)

Anybody else have this issue? Is it just a matter of waiting a few min with everything off, or is there a problem for the dealer to fix?
.
Thanks.

Ditto!! 3 times!

Apparently, I didn't learn my lesson first time. Just like you, I also discovered that letting it sit for 10 minutes or so lets 12V battery gather up enough juice to get going again ( My analogy here is turning an empty ketchup bottle upside down for few more drops.)

 

[Velox003]

I would buy one of these in a year or two. Nice to have handy just in case my 12v battery decides to loose voltage for whatever reason.

Top 10 Portable Jump Starters 2022 (buyersguide.org)

I would get it sooner than later. It didn't take long for my battery to drain. I think less than 8 minutes of listening to the radio.

 

[Richard E]

I would buy one of these in a year or two. Nice to have handy just in case my 12v battery decides to loose voltage for whatever reason.

Top 10 Portable Jump Starters 2022 (buyersguide.org)

How big a booster pack would you need to start up the Sienna- would a smaller 1000A unit do it? They go from 600A to 3000A.

 

[wscan]

How big a booster pack would you need to start up the Sienna- would a smaller 1000A unit do it? They go from 600A to 3000A.

You don't need much since you are not running a starter motor. The smallest booster would be adequate. All it has to do is get the computers started and engage the hybrid battery contactor.

 

[bobo37]

I've got 117,000 miles on my 21 and I've had ACC on multiple times a day and sometimes after the auto turn off to conserve the battery at 20 minutes I turn it right back to ACC. Sometimes I'll sit an hour on ACC and I've never had an issue. Maybe I'm lucky, maybe I need to be careful going forward. I do have a jumper if I have an issue.

 

[breger1]

I don't use ACC only leave it ON. I have found with the A/C including blower off that it can go 20 minutes before the engine comes on. Therefore I don't even bother with the ACC mode anymore.

 

[fotomoto]

I've got 117,000 miles on my 21

Maybe I'm lucky,

You're driving approx. 50,000 miles per year. Your vehicle is ON darn near all the time and thus the 12v battery is almost always at optimum charge levels. Other folks who don't drive/use their vehicle near as much have weak(er) 12v health. Those that take a lot of short trips suffer the most. I bought a Prius from a little ol' lady who had to replace hers three times over a 6 year span while driving less than 40,000 miles (retired, in town only).