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Discussion Starter · #1 ·
I seem to be having an intermittent electrical problem with my 2004
Prius. There are times when I have what I call a "bad shut-down".
This is when I turn off my car and I know that when I turn it back
on, several of the electrical systems will have reset.
This is what I mean by a "bad shut-down".

I park, and turn off the car. I know it's bad when the dome light
doesn't come on. At this point I am not able to use the "smart"
system to lock the vehicle from the outside, and sometimes I can't
even use the power locks from the inside and have to lock the doors
manually. Then when I start the car, the clock on the dash board
has lost its time and reads 1:00, the gas gage is down to empty and
it takes a few minutes for the sensors to kick in and go back to
measuring accurately the fuel in the take, both the A & B trip
odometers reset, the mileage/gas consumption monitor resets to zero,
and the auto up and down feature of the driver-side window doesn't
work.

As I mentioned, the problem is intermittent. I have not been able
to identify a pattern. Bad shut-downs have occurred after going on
the freeway for over an hour to after a 5 minute drive to the
grocery store. I took a road trip recently where for the first 3
days I had almost nothing but bad shut-downs, then after the 4th day
of the trip and since then (for the past two weeks) nothing,
everything is fine. This happened once before, but the problem went
away. I had taken it to the dealership but they said they couldn't
repeat the problem. I have had the "stalling" thing happen, but got
the service bulletin to take care of that problem, and when I
brought it to the dealership to have the electrical problem looked
at, they said they did an additional recall job that was related to
the stalling thing, but different than the technical bulletin work
that was first done.

Has anyone had similar problems or occurrences, do you have any
recommendations?
 

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Sounds like the 12V battery needs replacement, or you have a bad connection to it. When in READY, the DC-DC will be able to supply the needed 12V, but out of READY and the car relies on the battery. If the dome light does not light when in ON (rather than DOOR), then it definitely is the battery or else the DOME fuse is blown. But if the latter was the case, your problem wouldn't be intermittent.
 

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Electrical problems

I experienced sort of the same thing yesterday after disconnecting the auxiliary battery to attach a power cable to the battery for a ham radio transceiver, which i generally operate at 10 watts or less.

I lost the trip meter on the current tank of gas, and the current mileage on the mfd, and all the warining lights came on, but was able to push power button again and all seems normal on this morning's commute.

In the 06, i don't know about the prior model years, the negative terminal of the aux battery is attached directly to the frame of the vehicle as ground. Perhaps, if that bolt holding the negative cable to the frame is loose, or maybe there is not quite an excellent electrical contact, i.e. with a star washer underneath the cable end to ensure good contact, then that would explain the intermittent shutdowns.

maybe trying an ohmeter to measure resistance from the negative to the frame?
 

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FYI, once you have your electrical problem solved, you may need to reset the driver door window automatic function.

To normalize the power window:
1. Push down the power window switch
and lower the window halfway.
2. Pull up the switch until the window
closes and hold the switch for a second.
 

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Discussion Starter · #7 ·
Update on Symptoms Electrical Problem

I have thought about the lemon thing, I sure hop it is not the case.
In regards to the dome light problem, this is what happens normally. I turn off the car and the dome light comes on for about 15 seconds and then fades to off if I don't open my door. When I am having my "problem", I turn off the car, and no dome light comes on, it stays dark. It happened again a few days ago, after not doing it for about 4 weeks. I have started making notes, and same thing happened as in the past, but I noted that my window auto up/down feature continued to not work for about 5 power up and downs (driving over 2 days), and then one time I turned it on, and tested the window and voila, presto magic, it works again. Does this still sound like a 12 volt battery issue? Another Prius user group told me I needed to contact a special engineer out of Torrance to check it out. What do you guys think? I really appreciate your feedback.

Oh, and I never disconnect my battery or plug anything into it but my cell phone charger.
Thanks again for your advice.
 

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How is the dome light when you put it to ON rather than DOOR when you experience your problem? If dome light does not light, you have a bad battery or wiring to it. When the dome light is set to DOOR, it is electronically controlled, which makes it inconlusive in determining the condition of your standby 12V supply. With it on ON for testing only, it is fed straight from the main 12V source (through fuses of course) and can be your test light to check on the 12V standby power source.

Of course don't leave the dome light to ON, otherwise you WILL drain your battery.
 

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I had the exact same problem on my 2005 Prius. Not only funny door problems, and car starting automatically when getting out of the car, and clock randomly resetting to 1:00 am, both when driving, and when parking, or starting... but also having the entire electrical system shut down so that the locks wouldn't work at all, and having to use the manual key to get in!

Sometimes the brake peddle would reset the system if held down long enough. It was a brand new 12 volt battery, and recently tested very good, so it wasn't the 12 volt battery being "dead".

When fully locked out, I would use the manual key, open the door, open the rear door on the driver's side (manually operating the lock by reaching from the front), put the back seats down, crawl to where the 12 volt battery is at the right rear of the vehicle, open the cover for the tail light access, and wiggle the wires, and the car would come right back on!

Well, I found the problem.... the dealer that changed the battery never bothered to fully tighten the +12 volt lug connection to the battery post! Apparently he didn't have the right size deep socket with an extension.

Everything pointed to a 12 volt "loose connection"; never expected it would be that they didn't tighten the connection to the 12 volt battery. It became apparent when trying to open the fuse container above the battery; you have to pull a plastic pin. Once that plastic pin was pulled, the whole fuse assembly rotated around the battery post! Wouldn't move at all if was tightened properly. (I also sanded down the car body for connection of the -12 volts to the battery just in case).

So, NO, it is not a "lemon", nor is it "ghosts", nor was it someone "hacking" the computer through blue tooth phone connections... (Even though the day before the problem started occurring it was announced on the radio that these "smart cars" could be "hacked" via all these "smart connections").

It took a couple months after the battery was replaced before the problem started showing up, so apparently it was "finger tight", but regular driving loosened it up enough to cause the intermittent problems.
 

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I seem to be having an intermittent electrical problem with my 2004
Prius. There are times when I have what I call a "bad shut-down".
This is when I turn off my car and I know that when I turn it back
on, several of the electrical systems will have reset.
This is what I mean by a "bad shut-down".

I park, and turn off the car. I know it's bad when the dome light
doesn't come on. At this point I am not able to use the "smart"
system to lock the vehicle from the outside, and sometimes I can't
even use the power locks from the inside and have to lock the doors
manually. Then when I start the car, the clock on the dash board
has lost its time and reads 1:00, the gas gage is down to empty and
it takes a few minutes for the sensors to kick in and go back to
measuring accurately the fuel in the take, both the A & B trip
odometers reset, the mileage/gas consumption monitor resets to zero,
and the auto up and down feature of the driver-side window doesn't
work.

As I mentioned, the problem is intermittent. I have not been able
to identify a pattern. Bad shut-downs have occurred after going on
the freeway for over an hour to after a 5 minute drive to the
grocery store. I took a road trip recently where for the first 3
days I had almost nothing but bad shut-downs, then after the 4th day
of the trip and since then (for the past two weeks) nothing,
everything is fine. This happened once before, but the problem went
away. I had taken it to the dealership but they said they couldn't
repeat the problem. I have had the "stalling" thing happen, but got
the service bulletin to take care of that problem, and when I
brought it to the dealership to have the electrical problem looked
at, they said they did an additional recall job that was related to
the stalling thing, but different than the technical bulletin work
that was first done.

Has anyone had similar problems or occurrences, do you have any
recommendations?
Some of the responders were on target, some not. Thankfully, JessPanama got to the bottom of it. But there's more if any have experienced what he did. No, the lemon thing is not how Toyota operates. Yes, it is an electrical issue. When a Prius is in the Ready mode, the inverter keeps the 12V battery charged which can suppress the effects of this problem. If the battery is bad/going out, as one responder noted, all kinds of strange things happen, including the "bad shut-downs", clock reset, auto window function failure, fuel gauge reset, etc. Also noted by one responder was a bad connection of the negative battery lead to the chassis. If it's loose or corroded, the 12 volts needed to start the computers and operate the relays won't be solid and, like a bad/about-to-be-dead battery weird stuff happens. What's worse, I don't think there is any error code generated from an intermittent connection of the 12V battery.

However, there is yet another, unusual way that the 12 volts needed to start the system can be intermittent, as I discovered. Why Toyota loaded the + terminal of the battery with a buss and fuses is not clear. What happens is this: the various parts that are connected to the hold down strap AND the terminal that clamps the + side of the battery must be in perfect alignment. Toyota engineers allowed some movement of all of that stuff on top of the + terminal relative to the battery strap. In fact, there are (2) holes in the battery strap that allow the stuff on top of the + terminal to be aligned with the + terminal in case the distance from the strap to the + terminal changes. How can this distance change? It is different from one brand of battery to another. If a dealer or an owner has to remove the battery for some reason and puts in a different one, the small push connector that joins the buss etc. to the battery strap should always be removed FIRST and then reinstalled in the correct hole. IF THIS IS NOT DONE RIGHT, there will be a constant force on the + terminal from the misaligned clamp. After some period of time (in my case about 3 years) the battery clamp gradually loosened, causing an intermittent connection and lots of very weird events and NO ERROR CODES. It was the DEVIL to track down. If got worse and worse. Finally, my wife and I nailed it. She sat down in the Prius on the driver's side, was able to get the READY light, stopped the system, opened the door, but NO DOME LIGHT. This is the clue that there is no 12V to the system. I had her stay very still, crawled through a door to the right rear, uncovered the 12V battery terminals, and wiggled the stuff sitting on top of the + side of the battery. The dome light popped right on and I had the answer. It was an easy fix. I almost bought a new 12V battery (+$200!) which was not needed. The Toyota dealer that JessPanama went to is about typical of 1/2 of the dealers: Unless the error is in the onboard computer, they're clueless and just start replacing parts until it works. That's fine if the car is under warranty. If it's not, you've taken a trip to the cleaners - and why these blogs exist to help protect us from the lazy and incompetent. Thank you, Prius Online and Prius chat.
 
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