Prius won't start...ready sign never turns on

Your drive times are WAY too short.

See page 8 of

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http://www.autoshop101.com/forms/Hybrid03.pdf‎

. The 12 volt battery type hasn't changed from Gen 2 to Gen 3, AFAIK. Notice the very slow charge rate? Also see my post at Dead battery at 400 miles | Page 2 | PriusChat.

12 V battery, gone for 2 months | PriusChat confirms 36 AH.

I strongly you suggested you get a battery tender or a decent charger that can properly charge AGM batteries such as the Optimate 4 I suggested. Charge it up w/that. If it doesn't hold a charge, you're going to need to replace the 12 volt and maintain it w/a tender or charger.

 

Let's not forget the basics. You need to check or have checked the 12V battery terminal connections for loose or corroded connections. Even if the connections look good it would still be a good idea to disconnect the 12V battery and clean the terminals, both on the battery side and the cables. One of the challenges you have with such a short drive is the engine is barily able to complete its warm up cycle.
In all reality though, since your Prius is so new with so few of miles I don't understand why you aren't calling your local Toyota dealer and asking them these same questions. You should also be able to email them. More than likely the service you need will be covered under the warranty.

 

The warmup cycle has nothing to do w/the 12 volt battery charge rate. It doesn't matter if the engine's even running or at what RPM.

As for the warranty, well, it needs to still be within the 3 year/36K mile warranty. I don't recall the 12 volt battery warranty OTOH. On Nissans (for instance), long ago, even though the basic warranty was 3 year/36K, the 12 volt was 1 year/12K miles and pro-rated after that until some # of years and miles...

 

Will true, the charging of the 12V battery from the traction battery isn't dependent on the ICE for the most part there is one thing the ICE is needed for. That is to charge the traction battery. During the ICE warmup sequence the amount charge the ICE provides is limited, especially in the first stage. If the traction battery gets down to 2 bars the system will likely limit charging of the 12V battery.

 

My 2012 is failing to go into " ready " intermittently. If the problem was the 12 volt battery how does that account for the failure to eventually correct and go into " ready " ( at least so far ) ? Seems the stoplight switch is the more plausible culprit. So... back to the dealership. I reported this issue to the service tech when we had the car in for the software update and he seemed perplexed and said to see if the problem resolved afterward. My wife told me today that she has had this happen 3 times since the update.

 

I agree, it is probably the brake pedal switch.

 

The frustration is that I took the car out today to run some errands around town and tried to make this glitch occur. I probably turned the car off and on better than 10 times and never could make it do it.

 

Because when the battery is dying, the voltage doesn't go down to 0; it might be 11 V, or it might have high internal resistance (so the voltage drops only if there is a load on it). Say it's the second problem, then the car might have trouble turning on right after you get in and the brake booster pump is running (dragging the voltage down). It might also have trouble starting for another minute, while the battery recovers from the drain - but then it would work again.

Similarly, if you had the car on recently, the brake system is already charged, so the pump doesn't run as long; additionally, the battery was recently being charged (i.e. the car was on), so the voltage is higher than if it had been sitting overnight.

That's not to say that it IS the battery - it's just not behavior that would be inconsistent with battery trouble.

 

I am so happy to have found this thread. I have been living this frustrating intermittent problem since last year. I have a 2011 Gen III Prius. It started on a cold winter day after several days on non-use. Car would not start. All electrical systems on and working but no Ready light. (Aha, you say, engine cold, battery weak, etc..) Alas, then it started happening on warmer winter days; then Spring days and even summer days. Sometimes rainy, sometimes not. Took the car to the dealers on multiple occasion, but because of the randomness they could never reproduce the problem. They checked/changed the brake light; they charged the battery; to no avail. My one saving grace is that I found out I could "force start" the car by pressing the Power Button for 1o secs or so. As this was around the time of the software upgrade (Spring 2014), the dealer said let's see if the problem persists after the upgrade. Alas, it did not solve the problem. At first, all seemed fine, but then again at rare random times, the ready light would not go on. It would take multiple attempts to start the car. the worst thing: since the upgrade, my "force start" procedure no longer works, so if the car doesn't start, I really am stuck. I just have to keep trying until the ready light turns on.

Over the past summer and up until the past few weeks, the problem was very rare but it is now coming back with increasing frequency. Temperatures are getting colder, and sometimes the problem seems more apparent of rainy days (or is that just a coincidence?). This week the problem has struck three times already.

One thing I have noticed since the beginning is that when the car does start, there is a click noise coming from the right rear of the car where the battery is. When I hear that click, I know the ready light will come on and the car will start.

I have to take the car back to the dealer to try to resolve, but I want to gather as much info and insight to help them solve the problem. Last time, they had no clue as to what was wrong. I am also beginning to document each start (Date/time/temp/weather/etc..) to see if there are any patterns that emerge. I have also taken videos of the instrument panel (dashboard) during the unsuccessful start-up process.

I may try charging up the battery to see if that helps. A weak battery does seem like a plausible cause, though last year the dealer already tried that solution to no avail. I would love to rediscover how to "force start" the car because that at least will not leave me in the lurch. I'll let you know how it goes.

 

Our Prius has not done this to us for several months now ( but we don't drive it daily - maybe twice weekly on average ). Good luck in your quest for a firm diagnosis and cure. If you are successful please post an account here. I and others are very interested in learning the root cause of this intermittent malady.

 

Could this be a relay that's failing?

 

Now that my wife and I are both fully retired, our two hybrid cars do no get driven enough to keep the 12V batteries fully charged. I don't have a battery maintainer, but I do have a large automatic battery charger, so about every ten to fourteen days I charge both batteries. This keeps the 12V batteries charged and healthy. If you don't drive enough or use a charger to keep the 12V battery charged, it will fail prematurely, especially the OEM Prius battery.

An undercharged or weak battery is most often the cause of Prius hard/no start problems.The best course of action is to start with the basics, rather than guessing about relays and switches. When a relay or switch fails, it usually goes out completely, not intermittently. Replace the battery, buy a battery charger and use it if you don't drive enough to keep the battery charged. I replaced the OEM Prius 12V battery with an Optima in January 2014 and it has not given me any trouble.

 

Our Prius did this to us again a couple nights ago. I turned the ignition off and waited several minutes and then when I tried again it went into "READY " and we were good to go. I don't get how the 12 volt battery could be the cause of this. This problem has never occurred at the initial start up - even after the car has sat for days without being used. This has always happened after the car has been driven some distance to a destination. The condition presents itself when coming back to the car to restart and continue on. It would seem to me that the 12 volt battery would be most depleted after sitting unused for several days and that after driving with the ICE engaged for several miles the battery would be mostly replenished. Is my logic correct here ?

 

A normal 12v battery last around 4 to 5 years. If yours is more than 5 years old, it would be reasonable to think it's dead

 

Maybe you're starting to get intermittent problems with a brake switch that's going bad?

SCH-I535

 

describe several miles. it maybe that a few miles taxes the battery, and many miles are needed to recharge it.

 

A few miles in this context would be less than 5. That is across our rather small town.

Our prius is about 2 1/2 years old with 14,000 miles.

There is a forum member here that had his brake switch replaced by the dealer and that did not prevent intermittent recurrence of the problem.

 

P.S. Coincidentally, I received a JD Power survey request yesterday in the mail regarding our 2012 Prius. The only bitch that I have with the car ( other than the worthless navigation system ) is this irritating and frustrating intermittent (and self correcting) failure to go into "READY ." mode.

 

I'm curious to know if anyone has found a definitive "fix" for this problem. By that I mean finding the exact cause and after repair having no further issues with failure to go into "ready" mode when attempting to start the car.