Starting problems

Replace the 12V auxiliary battery.

 

In case you were wondering why the car starts sometimes and why it doesn't at other times: the 12V battery apparently is at a marginal level. The battery produces electric power from a chemical reaction, and chemical reactions speed up at higher temperatures.

When the battery is warmer then it will produce more power. If you try to start the car later in the day after the battery has a chance to warm up, there's more likelihood that the car will start.

I also suggest that you review the jumpstart procedure used, as it should have worked. There's something wrong with the way the jumpstart was implemented. Perhaps the jumpstart cables are bad. Perhaps a cable connector did not properly connect with the Prius dedicated positive jump start terminal, etc.

 

Just a thought. . .

Every time you try to start it, it fails? Every time your husband unlocks it with his remote and starts it, it starts fine?

If it isn't the 12V battery, is it possible that your smart key battery needs to be replaced, but your husband's is still ok?

- Danny

 

Good point, it is an excellent idea to ensure that the fob is not part of, or all of the problem. If the OP was able to enter the car using her Smart fob in the usual way, then I assume the fob battery had sufficient power so that the fob would be recognized by the interior receiver and the Smart ECU. However it doesn't hurt to rule that out as a possible issue.

 

Wow, this is a strange one. Can you tell us, do you have Smart Key, or regular keyless entry? If Smart Key, are all of the smart functions working, such as unlocking the car by touching the door handle? In either case, have you tried all your keys?

The fact that your interior lights work means that the fusible link is intact and you don't have a reverse polarity problem, which is good. But you are getting into repair shop territory, i.e. combination meter, if our simple suggestions don't help.

 

I'm thinking it's dying FOB batteries.

 

Don't despair - your 12V was probably on its last legs, anyway. You've just saved yourself being completely dead in the water at the worst possible time. Four years is a long time for these batteries.

Try replacing the fob battery, too. :thumb:

 

If the car won't start you can also eliminate the fob batteries as a cause by putting the fob in the slot in the dash and see if the car starts. If it still doesn't start then its not the fob battery.

 

1. Turn on the headlights and see how bright they are. Then turn off.

2. How much fuel in the fuel tank?

3. Can you cycle through IG-OFF, ACC-ON (where the MFD turns on) and IG-ON (where the instrument panel warning lights are all on) modes by repeatedly depressing the POWER switch without depressing the brake pedal?

If there are no problems evident from the above, then press hard on the brake pedal, press the POWER switch, and see if the car will become READY.

If not, then looks like you'll need to tow the car to the dealer for help.

 

This question is absolutely vital to diagnosing the problem. Vivamom you really should have given this information right at he very outset because the answer totally influence what are the possible causes.

 

i gotta wonder about your brake switch. perhaps you don't press as hard as your husband.

 

+1 regarding pressing on the brake pedal hard, as you press the POWER button.

Should you have a future recurrence of the problem, I suggest that you try #3 from my post #12 above. Should you find that you cannot cycle through the three modes, that will provide an important clue towards solving the problem.

 

When you say "no signs of life", did the cabin interior lights come on? Do the headlights appear bright? (This shows that the Body ECU works and the 12V battery has sufficient power to light up the headlights.)

Was it possible to cycle through ACC-ON and IG-ON or was the car totally non-responsive when you pressed the POWER button? If the latter, my guess is that the POWER switch might be bad. If that is good, then it is possible that either the Transponder Key ECU or the Power Source Control ECU is flaky and needs to be replaced, assuming that the headlights could be turned on and are at normal brilliance, as stated above.

Since you inserted the fob into the fob slot, without any improvement in symptoms, that rules out the Smart Key ECU as a potential issue.

Let's see what action plan the dealer develops on Tuesday, since they also have experienced your car's no-start symptoms and cannot say that the problem is due to driver error. Hopefully the car has logged a DTC that will provide a clue as to the root cause of this problem.

Suppose by tomorrow the problem goes away and they say they can't find a cause so they want to return the car to you as-is. You might decide to ask them to start "throwing parts at the problem" by replacing likely parts such as the POWER switch, Transponder Key ECU and the Power Source Control ECU. However, since your car has 70K miles, unless you have extended warranty coverage, you'll be charged for the repair. Good luck.

 

In a way, this is a relief. At least the car is demonstrably broken while at the dealership. I meant to mention a couple days ago that there is an issue with the IG1 relay becoming frozen at very low temperatures but it sounds like that is probably not the case here from the latest news