2005 Prius Will Not Start....Sometimes....

OK, I see you are going to get a battery. Be advised when you disconnect the battery you will loose all your radio pre-sets and the window auto-down will be unhappy. The window is easy. Roll down 1/2 way, then roll up and hold up switch until it beeps. The radio is your baby.

As for the battery install:
Remove hatch floor then cargo container.

Remove small cover over the battery on the right side.

Now you can see the battery. Remove the negative cable first. This is to ensure that any slip of the wrench will not result in disaster (if you ground the wrench there are no consequences as you are working on the ground). Once the negative is disconnected, the positive terminal can be accidentally grounded with no consequences. Do be aware that there is a large capacitor bank (to enable emergency braking in the event the battery disconnects while driving). It's the large black device in front of the battery. It will be charged and may discharge if you short it.

You will have "fun" getting the red cover off the positive terminal. Be patient and work it off.

Take care to reconnect the battery breather tube.

It's easy enough. You just have to have some patience.

 

It actually is unnecessary to remove the red plastic cover. Just bend it up enough to gain access to the battery positive terminal.

I suggest that the OP remove the brake power supply which is adjacent to the 12V battery. It is not necessary to remove the wiring harness connectors. Just remove the mounting hardware and place the power supply out of the way when removing the 12V battery.

One difficult step is reinstalling the traction battery vent duct which runs over the 12V battery, without dropping the screw that holds the duct to the fender. It might be useful to have an extendible wand with magnetic tip, to help fish around for any hardware which is dropped into the fender.

 

Oh sunking, please do not misunderstand my response. If that made you feel uncomfortable, I apologise. Reason was you never mentioned your car was all the time taken care by your dealer until this message. Well I have my pre own beauty for three years. It never gave me ANY issue as well. Like yours. Very reliable and made me happy when driving it. Average gas millage is 49. Just changed the electric collant pump per the LSC and also done the transaxle fluid exchange( it runs more smooth and quieter). So did have you done your LSC and fluid exchange( which is our usual practice every 60000 miles.)?
Continue enjoy you nice baby. Regards.

 

What does "MFD" stand for in this context?

 

Multi-Function Display

http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html - I'd suggest checking it only after the car has sat many hours, preferably overnight.

 

Good thread. Waiting to hear if the new battery fixed the problem. I still have the original battery in my 05. Voltages look good however.

 

Interesting. It sounds like the immobilizer ECU might be flaky, where it takes some time to recognize that the fob is authorized to start the car.

If you can easily replicate the problem then I would say it is time to visit the dealer. However if the problem only happens once every three days then when you take the car to the dealer it will probably work great and "no trouble found" along with a repair invoice for one labor hour of the tech's time will be the result.

These intermittent electrical problems are the worst to have since the root cause is so hard to pin down.

 

Interesting. Do the voltages still look to be in the OK range? Maybe a parasitic load is draining the battery?

 

Hey OP,
Are the brake lights coming on when you try to start the car? If not the switch may need adjustment? My understanding is that the brake switch gives the OK to start? I may be wrong on this, but we should find out soon enough!
Cheers;
Hal

 

I just changed my auxillary battery in my 2005 Prius which I bought used in October, 2010 with 111K. I used several You Tube Videos made by other Prius owners for assistance. They were very helpful. Make sure that if you do it yourself, you call several Toyota Dealers for prices. I bought mine for $ 138.60. One dealer was telling me that it was $ 346.00. Due Dilligence is required.

 

The immobilizer ECU reads the fob's unique ID and verifies that the fob is authorized to start the car.

Since you say that even when the fob is inserted into the dashboard slot, the car will not start, then the Smart antenna in the car (located in the center console) would not be the issue.

Another poster suggested that the brake pedal switch might be faulty. If that were the case then you should at least be able to make the car ACC-ON and IG-ON, when pressing the POWER button.

If nothing happens when you press the POWER button, then the brake pedal switch is not the issue.

Yes, you could ask that the immobilizer ECU be checked but if the no-start symptom does not exhibit itself when the car is at the dealer then NTF will be noted by the tech and nothing will be done.

 

Just to be clear, there are two ECUs: immobilizer and smart key.

Please check all 12V battery connections. Often, a loose terminal or loose/high resistance connection of the negative wire to the body will cause trouble.

 

Was there any other jobs done on the car recently, any extras fitted that mite interfere with the electrics of the car?,
Theres a main relay located under the dash that powers up IG1, 1G2 and MDF etc when you go to start the car, I had a issue with one before where the vehicle was stuck in park and would not power up , And this relay was the problem, Did you get the fault codes checked ?

 

Must have been a brain fart as OP is not talking!.Hal