Prius will not start = Bad brake light switch?

To all such posts here on PC, someone will always ask how is the 12V battery? That is the first thing to check, although it looks like you have your finger on the pulse.
Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF | PriusChat

 

There were a few 2010 owners that reported early issues with the brake light switch adjustement. IIRC there are two switches behind the brake pedal. One is for the brake lights and start circuit and the other is to disengage the cruise control.

It may be as simple as re-adjusting the brake light switch since once the brake light is visible you are able to start the car. If the adjustment is OK then you will probably want to replace it.

 

n/a

 

Well as you said,your problem was due to a warn out switch. Bad contact. That's it.

 

Toyota parts are not particularly expensive and I personally would avoid aftermarket.

 

I have a Prerunner in the shop with a bad Taiwanese throttle position sensor that another shop put in two months ago. I hope that answers your question.

 

2008 Prius - exactly same symptom. I thought it was the brake light switch, so (super confident !!) walked into the dealer and had the switch replaced. It started w/o problems for a few weeks.
I also have another symptom: when I brake (in the dark) - I can see the brake light come on and off, sometimes like a strobe-light - and the whole car shakes like it was an earthquake. If I put the shifter in Neutral - the light still blinks, but the shaking stops completely, and only comes back if I put the car back in "D". So I may have a slightly different problem, but it sounds like you are on the right track.
I will try to order a switch (the same) online. (much cheaper)
(Read somewhere that there are 2 switches) Not sure if this helps. Oscar

 

Stubbegubber.

It sounds as though you have a drive shaft CV problem as the shafts are not loaded in neutral when braking, the only thing slowing the car down are the discs. In drive the discs are not working "under normal braking" and the drive shafts are loaded as the MG's slow the car through the transmission and drive shafts.

I believe it will be one of the inner joints but it could be wheel joints.

 

Question: Why would this same CV joint problem not show up when accelerating?

Question to StubbeGubbe: Is the frequency of the shaking dependent on the car's forward speed? Does it slow in frequency as the car slows?

With the blinking brake light symptom, there might be something else going on.

 

I have have personally come across this same problem on a front wheel drive car (not a Prius) that when accelerating everything was fine but as soon as the accelerator was released "engine braking" heavy shaking began. This after long investigation proved to be an inner drive shaft CV joint.

The problem was that one of the cups that hold the needle rollers had broken up. When the engine was driving the shaft all was well, but when the shaft was driving the engine it moved over to one side and ran in eccentric circles causing the car to shake.

 

No, the frequency does not slow down. If anything, it increases as the car comes closer to a stop, but that may just be my perception, as the shaking seemingly gets worse.

There is more info... (forgot to include it in the initial post - sorry)
(Also, a definition: When I say that the car "starts" or "does not start" - I am referring to that it only cycles to the stage where one can operate electric components, such as windows, but without the ability to put the car in Drive, and start going..)
- The issues with the blinking and shaking seems related, since when the brake lights are not blinking rapidly during braking, there is no shaking. The shaking also seems very close in nature to the shaking that goes on when I brake over potholes or uneven surfaces in the road, i.e. the ABS/release of the regenerative braking happens, to avoid the wheels from locking up. Also, when the car decides to "blink and shake", there is also problems starting the car ( /brake lights does not come on).
The way I get it started, is by either..
(1): - Pressing the brake pedal repeatedly until I see (if it is dark, or there is a reflective surface behind the car) that the brake light come on. (It always starts if the brake lights come on)
(2): Press the brake pedal harder, until it (almost?) bottoms out, i.e. if I were to press it this hard during braking, the car would stop almost momentarily, and the ABS kicks in.
- Recently - 2 things have materialized.
(1) - The shaking/blinking problem can also be gone for several days, and then come back for a day, or a week.
(2) - When it is dark, is that sometimes when I slow down, the car can come to a complete stop, without the brake lights ever coming on. If then, after I have stopped, I push the brake pedal as hard as I can, or slightly less, the brake lights will come on. This realization made me think that I should get this issue fixed sooner than later, in case I get a car rear-ending me, and blaming it on that there were not brake lights coming on.
- I am just reading up on the car in a Haynes manual - and there is mention of a "Pedal Stroke Sensor". (It tells the ECU "how much effort I put into braking".
- I am starting to think there is an issue with this instead of the brake light switch, otherwise I think the car would not differentiate between how hard I push the brake pedal.
- Also, recently, it has started wearing on the brake pads, as in the first 100.000 miles or so, (currently it has 127.000 miles) - they always said at my dealer's service-dept, it was not possible to see any wear at all. (I rarely use the brakes to stop the car, other than maybe from 10-15 MPH) The increased wear, would also make sense if the car does not use the regenerative braking, (as much, or at all) due that it is not being "told" by the "Pedal Stroke Sensor" to use it.
- Online, there is also mention of a "Brake Pedal Position Sensor" [p/n: 89510-47010] - Is this the same as "Pedal Stroke Sensor"?
I just realized that I may have hi-jacked this tread, and should have opened a separate one... (but it seems(seemed) to be similar in nature)
Thanks again.

 

The service manual uses the term "Brake Pedal Stroke Sensor".

It is possible to help sort this out by using an OBDII to USB adapter, and running Prii_dash software, which is in another forum on this site. One of the sensors it monitors is the brake pedal, and it would be possible to see what the system thinks is going on from it's side of the sensor. But if you want this sooner, then you might have to go for taking it to a shop. Braking problems are not something to tinker with.

You replaced the brake light switch, but report that the brake lights may not come on, yet the car comes to a stop. The brake light circuit is the standard 12V->brake switch->lights->ground, without any ECU's involved. If there is any situation where the brake lights do not come on when the pedal is touched, then that circuit and switch is still not right. Tracing it with a DVM should find a problem. Get that working and go from there, would be my suggestion.

Fill in your location in your profile, maybe there is an independent mechanic near you that can help.

 

PriiDash does show the brake pedal pressure sensor reading but that's different from the brake light switch. In a future version I can add the brake light switch if possible.

 

Right. I think the brake light is somehow still the root of this situation. The brake light switch output goes to the Skid Control ECU directly, as well as powering the lights. If the brake lights blink, then the ECU is getting that same signal as input, and who know what the effect will be.

Prii_dash might be able to help and say that the brake pedal sensor is OK, and limit the troubleshooting a bit more.

 

Brake light indicator added. See this post:

PriiDash(TM): Enhanced Instrument Panel / Data Logger - Now Open Sourced! | Page 4 | PriusChat

 

Last update and fix for me... - (took it to Toyota of El Cajon, near San Diego, after it would not start at all, at last) - They said that there was a connector having to do with the installation of the Karr car-alarm system, and the engine kill function. I must have affected the intermittent contact when pushing the brake pedal, and also explains why the symptom came and went.
(Another local Toyota dealer where I bought the car, also did the alarm install, and I was also treated so badly that I never went back....) So.. - they screwed me over one last time, five years later, for another $350, that this repair cost me.
Thanks again to Toyota of El Cajon, who always has helped me out, has a great attitude, and even covered the charge for the rental car for the two days :-D