starts then dies

Hi Tony,

A few questions for your consideration:

• How many miles did you log on the car before deciding to clean the trunk?
• How did you clean the trunk - was water or other fluids involved?
• Have you securely tightened the battery connections?
• Do you have a digital voltmeter; if so, what voltage does the 12V auxiliary battery produce?
• Do you have access to an OBD-II code reader?

 

Purely a piece of completely uninformed and tired wild guessing (from someone who just this moment walked in the door from the first 500 mi road trip in the Prius) - would it be possible that in the process of cleaning the trunk the *skinny* wire that attaches to the aux battery positive terminal fuse block got disturbed? The skinny wire attaches via a small two-pole plug (the other pole isn't used) and is also fused (of the two fuses in that block it's the small one, not the 120 A one).

The skinny wire is used for voltage sensing to regulate the converter output. A problem there might cause the system to go into READY and then after N seconds say "hey, I can't see my intended charging voltage, something must be wrong."

Again, I'm mostly grasping at straws - getting hold of an OBD-II scanner would be the more promising way forward.

-Chap

 

Hi Tony,

When the car is IG-OFF, the battery should be at 12.6V or better. A marginal battery can cause weird electrical problems, so it would be great if you could replace it.

If it turns out that this is not the problem, then you'll need to buy an OBD-II code reader to get some clues about the nature of your problem - or else have your car towed to the local Toyota dealer. Note that some generic code readers may be confused when plugged into Prius due to the multiple ECUs that potentially can produce trouble codes.

 

Well, I liked my theory, but I tested it this morning ... I disconnected the sense wire at the aux battery terminal and started the car ... ran just fine, no warning light, no code that my generic OBD-II scanner could see.

Then I kind of wanted to see whether my generic scanner would even be able to pick up a HV diagnostic code if there were one, so I looked through the DTC pages in the manual looking for some easy way to cause a code, and I did succeed in getting a triangle-exclamation-point and car-exclamation-point, but my scanner was still not able to read the code. Nuts.

I know it takes something like a Toyota scanner or a Graham scanner to read the specialized HV parameters, but is it the same way with reading the DTCs? Can anybody recommend a generic scanner that IS able to read DTCs from the HV ECU?

-Chap

 

Hi Tony,

You will probably find that the terminals from a regular 12V battery are too large to fit the Prius battery connectors. However if you can figure out how to connect the battery, you can use it for testing purposes.

Hi Chap,

What would be interesting is if you could hook up a digital voltmeter across the battery to read the voltage produced by the DC to DC converter when the Prius is READY; then disconnect the sense wire and see how much the voltage changes.

Regarding the generic scanner, my OBD-II scanner was successful in picking up a DTC produced by the traction battery ECU, but theres no guarantee that it would work under other scenarios. I owned the Ecrostech (Graham) scanner when I still had my 2001, and highly recommend that if you can locate and buy a used one.

I'm wondering what you did to produce a DTC.

If you want to produce a DTC from the engine ECU, you could disconnect one of the spark igniter connectors or the mass air flow sensor.

If you want to produce a DTC from the traction battery ECU, you could remove the orange interlock switch on the driver's side of the battery.

 

Remember that "runs, then dies" could be a no-start condition
from the git-go, i.e. it wasn't running at all but simply being
cranked for those few seconds after which the HV ECU gave up.
.
Check the 12V, check that something didn't get dislodged in the
cleaning process like a harness connection, and have a look down
the throttle body. Pull codes if possible, although the ones
of P3190/P3191 class meaning "engine does not start" may not
be amazingly useful. Without more in-depth info it would be hard
to do much more in terms of diagnosis over the net...
.
_H*

 

I thought of trying that some time, but yesterday I was focused on finding out whether it would cause any symptom like the OP's (and, secondarily, whether my scanner could read any code that resulted).

My first try was to unplug the inverter water pump, expecting a P3131 (inf 346). (Was the Graham scanner able to get INF codes?)

That condition didn't get detected in several minutes in READY. I don't know how it's supposed to detect a pump malfunction, but apparently it's not something direct, like a flow switch, so I assumed it would be detected by actual overheating of the inverter, and my curiosity wasn't strong enough to want to force the issue.

My next try was to unplug the circuit-breaker-sensor. That got immediate exclamation points. My crystal ball tells me the DTC was P3135 (inf 349), but my scanner just told me "no codes."

I had a similar idea and unplugged the #4 injector. I thought of the igniter first, but I figured the cat. would be happier with a non-fueled cylinder than with an unburned, fueled one.

The engine cranked over, ran a little, ran more roughly, ran very roughly, then stopped with a check-engine and both exclamation points. My scanner then retrieved only a P3191 ("no start" - go figure) which surprised me because I was hoping for something more specific (maybe a P0304) and I wasn't sure which ECU responded with the P3191.

I wonder if maybe my scanner just shows the first mode-3 response it gets from any ECU, so if that one has a DTC count of zero the scanner's convinced there are no codes, or if the first reply had only one P3191 in it then any other reply gets ignored. Hmm. I think I'll have to get some elm-based adapter and poke at it more directly.

I also loosened my fuel filler cap and left it loose to see how long before that's detected. (Several trips now and counting - isn't the ECU supposed to periodically do a vacuum check for that? How often?)

Or even just, I suspect, flip its little orange handle down without removing it; the handle seems to actuate a microswitch that's in the interlock circuit - I'd expect a P3140 from the HV ECU, but I haven't tried it.

-Chap

 

Hi Chap,

I see that you have been carefully studying the repair manual. That's great!

I don't think that the hybrid vehicle ECU has any way to know that the inverter coolant pump is inoperative, except when the inverter overheats.

The Ecrostech scanner does not pick up the INF subcodes, only the DTCs.

Yes, the engine ECU is supposed to detect a bad fuel cap gasket or an air leak. Not sure why it is taking so long for a DTC to be logged there.

 

Yeah, you'd think they would have thrown in a coolant flow sensor
or something to get an earlier warning, since it's really really
important to keep them big ol' transistors nice and cool...
.
_H*

 

Yeah, it's weird, though, because they've reserved two distinct INF codes for failure of the water pump or of the cooling fans, so they must think they have some way to distinguish the two. I wonder if they compare the various temp. readings in the inverter and MGs - if they're high and sort of uniform, bet on the fans, high and very different, coolant flow?

Finally got it on the way home from a friend's just now, P0440, P0441, and P0446. The scanner did read and clear them ok. So it took several trips and about a day and a half. (I suppose if the code has a twice-detected threshold, the test might be done on the order of once per day.

-Chap

 

Hi Tony,

Before you declare victory, I suggest that you wait until you've had a few more "cold starts" and see if the problem reappears.

 

The symptoms are consistent with a sticky throttle plate.

GOOD LUCK!
Bob Wilson

 

Bingo - this just happened to me, last week. I had disconnected the 12V battery several previous times without incident (the first time was when I added the cruise control, and used the opportunity to take the battery completely out and clean everything). All previous times when I have disconnected the 12V battery, I've just hooked it back up, reset the clock and radio, and had nothing odd happen.

Last week, though, I disconnected it just long enough to wire up a little 12V inverter in the trunk. (I've been following various descriptions of "PriUPS" large inverter installations using the HV battery, but that's all future for now, and I had the little one lying around and figured 400W is better than nothing in the meantime. I put a ring terminal on a pigtailed fuse holder, and attached it to the bolt on the load side of the 120A fuse.)

So I only had the battery disconnected long enough to do that, and I'm quite certain I didn't touch anything else. When I hooked everything back up, I started the car, it ran about 15 seconds and shut down with exclamation points.

The only code visible was the oh-so-helpful P3191. I used the scantool to clear it, the warning lights went away, I started the car again and there's been no trouble ever since. So I suspect there's just some rare confused state the ECUs can get into sometimes when power's restored, and it might not mean much.

Hmm ... I know the combination meter boots up with a flashing fuel gauge and takes several seconds to recover a correct reading. I wonder if a problem could sometimes result from going into READY while that (or some other slow boot-up process) is still going on.

-Chap

 

Having just replaced the 12v accessory battery in my 2002 Prius, without using a keep-alive, I can now recommend using one.

I did find that, after having the "engine stall after about 15 seconds" 'failure', that: shutting off the car, turning heater on, restarting, then putting foot on brake, car into drive; the car stayed running. I let it warm up and recharge the batteries (HV & 12V).

This may also apply to the 2001 and 2003 (noted here just for searches to hit).