PRIUS STARTUP WOES!

could be. sounds like a short somewhere. have you owned it since new? do you have lemon law in your country?

 

check with consumer affairs in the ag's office. in mass, if you take it back three times and they can't fix it, you get a new one.

 

you need a sophisticated electronics company to find an intermittent short. could be in an edu, mfd, power button, who knows? i'm just guessing. unusual problem, that's for sure.

 

if jumping it works, that points to the battery. have you tested it when it won't start?

 

Just one stray wire strand or a tin whisker somewhere can result in a parasitic drain either in the wiring harness, a connector or on the inside of a circuit board.

Most often, the issue is in the wiring. The troubleshooter must disconnect each fuse at the block and connect an ammeter to each circuit to measure for any phantom micro amperage drains. When the offending wire or circuit is found, it is either repaired or replaced with a NEW wire.

Another method is to remove the fuse to one circuit at a time, wait for a period of time to pass, plug the fuse back in to see if the car will start. If the car starts, that is the faulty circuit and/or system with the offending component. If the car does NOT start, the circuit for the pulled fuse can be certified as not the defective one.

In the case of a no start, the battery can be maintained with a Battery Tender or Battery Minder.

It takes a patient person with a lot of time on his or her hands to find the fault, but it can be done.

Apparently, the dealer would not rather spend the time or its technicians do not have the skill to do so.

 

I have this exact same issue with a 2012 Prius 2. I've found that opening and closing the doors a few times gets the car to kick back on into accessory mode as if I've pushed the start button and then I'm able to start it and drive.

A few weeks ago I was having issues with starting up the car that seemed like classic symptoms of a failing 12v battery so I bought a new one from the dealership installed it, and the problems went away, and everything was fine for a couple weeks. Then a couple days ago I was going to the car and my FOB wasn't unlocking the car. So I manually unlock the door and get in and try to start the car but there was absolutely no power at all. As I'm sitting there pushing buttons, trying to turn on lights, putting my foot on and off the brake, my girlfriend opens up the back passenger door and the whole car stars up into accessory mode like I just pushed the start button. The car started and ran fine and we were able to get home. However, when I got home I noticed when I pushed the power button to turn the car off everything shutdown immediately, no trip summary, no dome lights coming on, nothing. I tired starting the car back up with the power button and again nothing. So I got out opened and closed the back passenger door a couple times and the car started up into accessory mode without me pushing the power button. I got in the drivers seat and pushed the power button to turn the car off and this time it went through it's normal power down process, trip summary, dome lights, etc. The next morning I go to the car it unlocks, I get in, and just as I go to push the power button I lose power. So, I try the door trick and the car powers on into accessory mode and I'm good to go. I've had to do this almost every time I've needed to take the car anywhere over the past couple days, a couple of times the car has started normally without the door trick. I've made an appointment with the dealership for tomorrow morning, but any tips or advice would be greatly appreciated.

 

Just got back from the dealer. Naturally, the problem I'd been experiencing for several days in a row disappeared when I took it in for diagnostics. If I begin experiencing the problem again they want me to bring it back in for an overnight. So, unfortunately no conclusions as to what was causing my start up problems.

 

check the 12v terminal connections and negative to chassis point for cleanliness and tightness. might be something else loose though.

 

I agree. The "door trick" may be actually moving a loose connection...

 

I think this was it! I've given it several days and the issue hasn't presented itself again. I checked the connection to the negative terminal and I noticed the top of the connector was maybe a tenth of so of an inch above the post, the post and connector are about the same height, so I made sure it was down as low as it could go which was about flush across the top. One unusual thing that happened when I was adjusting the connector, there was a crackling sound and wisp of smoke. Not sure what that would mean other than there was some issue with the connection. So if anyone experiences a similar issue in the future definitely readjust the connection to the negative terminal.

 

you can get sparking when working around batteries. best to disconnect the negative, do the positive work, and reconnect neg. and wear safety glasses! all the best.

 

As they say, "Aha!"

Helped out a co-worker a year or so ago. He was complaining that his (conventional) car kept on losing charge, weird things happening, etc. So I went out to the lot with him, carrying a handy voltmeter. (We work at a place with a lot of electronics..)

I was looking around under the hood and put my hand on the battery - and darn near burned my hand on the positive terminal. What the heck?

Turned out that the battery connector itself was faulty. The battery connector on most batteries consists of a block of metal with a slot on one side and a bolt that squeezes the slot shut when the connector is placed on top of the battery terminal. Naturally, the rather large gauge, stranded wire that, in this case, was taking the battery current out of the positive terminal to the rest of the car, is swagged into a hole in the metal block at the time of manufacture of the wiring harness. Said wire was loose in the hole, leading to high resistance and a really hot terminal and battery post (which probably wasn't doing the battery any good). A new battery terminal fixed the co-worker right up; luckily, the plastic at the top of his battery wasn't melted, quite.

Getting arcs and sparks when moving the battery terminals around isn't exactly abnormal, but it's not exactly normal, either. So I got my suspicions about your battery terminals. With the car running, put a voltmeter right on the positive post and the other lead on the wire going off to the rest of the car; the difference in potential should be in the low millivolts. Check the negative terminal in the same way. Anything above a 100 mV is cause for excitement... and, if either terminal is hot, you're on to something.

Note that this kind of "diagnostic" isn't the kind where one plugs an OBDII instrument into the connector in the car - it's actually going out to the battery to check. So, if the dealer's people weren't doing that, they might have missed the issue. And replacing a battery isn't going to fix a high-resistance terminal.

Next: There is such a thing as a clamp-on ammeter, which measures electrical current. I don't actually own one, although at work they're here and there all over. They've got a squeeze grip and a circular, insulated pair of jaws that are designed to clomp over a wire. Squeeze the grip, the jaws open up; put some random wire inside the jaws; then let go the grip and the jaws encircle the wire in question. Any current (these things typically measure DC or AC, depending upon switch settings.. You'll want DC) will read on the display. With a Prius in Off there shouldn't be more than a couple of hundred mA being drawn. If you've got amps being drawn, well, "That's your problem." At that point one heads to the fuse box and starts popping fuses in and out one at a time until you find the circuit with the Evil. Then one finds a schematic somewhere and starts pulling connector plugs to find the area where the semi-short or what have you is located. Could be a component; could be a wire semi-shorted to a bit of metal, that's the fun with troubleshooting. One of the posters above made noises about how opening and closing doors on his car made the trouble go away; chances are, flexing the wires going into the door or flopping them around on the inside is what's doing this. Gad, I hate intermittents.

Good luck!

KBeck.

 

First, it's unlikely you would be able to initiate a battery explosion on a Prius battery. It's vented -outside-. But yes, it's always good to be safe.

Second, when replacing a 12V battery, BE SURE to clean the oxide off the terminals before you put the cables on the battery. I know the SAE terminal cleaners don't work very well on JIS terminals, but emery cloth does. Also, DO check the negative cable where it bolts to the chassis. That bolt can work loose.

It sounds to me like both of the above cars had issues with the 12V battery connection(s). It could even be the in-line fuse from the battery to the car is intermittent. I've seen that before.

 

It can be many things parasitic draw, fuse issue, battery issue, wiring issue. I changed all my lighting to LED to reduce voltage draw, checked all the fuses and last but not least changed the 12v battery. So far so good.