HI,This is may 1st post. I have a 2001 prius and it won't start.

1. Can you turn on the headlights, and if so are they bright?
2. Was the car working properly prior to its three-month storage?
3. Do the dashboard warning lights turn on, prior to your turning the key to the start position?

 

Has it been yours for a while, and you parked it for 3 months, but it worked before? Or did you just acquire it from someone who had it sitting for 3 months (and, why was it sitting)?

Do you have a ScanGauge II, the miniVCI knockoff thing, or any other way to read Prius-specific trouble codes from the computers?

Since you say the dash "goes dark" at START, I assume you mean that before you get to START, some of the dash does light up at ON?

Then, at the time you turn the key further to START, do you hear any clicking sounds from the back seat around the driver's side?

If you have a ScanGauge or other diagnostic scantool, it should also be able to show you the voltage on the twelve-volt system; you might post here the reading for just ignition ON, that plus headlights, that plus A/C blower, etc. If you don't have such a tool, see if you can use the built-in voltmeter to collect the same information.

Good luck,

-Chap

 

Hmm, it sounds like your car has a serious problem. If the dashboard display dims when you try to start the car, that implies voltage on the 12V bus is sagging at that moment.

If you have a digital multimeter you can confirm this by measuring voltage at some convenient point, perhaps at the auxiliary power socket, and see what happens to the voltage as you move from IG-OFF to ACC-ON to IG-ON to Start. The IG-OFF voltage needs to be measured at the battery or at some other live point, since the auxiliary power socket does not receive power at that position.

If the IG-OFF voltage is not at least 12.6V, then fully-charge the 12V battery first, and then see what happens.

 

If I'm not mistaken, it's normal for some of the IG-switched circuits to be interrupted while the key is turned to START - some stuff will go dark, the MFD reboots again when you relax the key back to ON. I'm not at my working Gen 1 to check, but that's what I remember. It doesn't mean the aux battery voltage is being hauled down, but only that the ig switch works that way (as it often did in conventional cars). So that doesn't concern me much.

The crucial thing is the mysterious incident of how the System Main Relay clicked when the key was at START.
"But the SMR didn't click when the key was at START!" Precisely, that's the mystery.

Possibly the SMR itself actually isn't working, or there's wire harness damage in the circuits actuating it, but my first guess would be that the HV ECU is choosing not to engage it, and has a reason it can report to you over a Prius-aware scan tool. One of the interlock codes, perhaps? I'd think checking for codes would be the easiest and most promising place to start. Poking around the SMR itself would involve a bunch of digging as well as your class 0 insulating gloves, but plugging in a scan tool is no sweat.

-Chap

 

Are there rodents in the area?

Bob Wilson

 

Are you using the exact same key you used when car was parked?
(i.e. one that is known good mated to the immobilizer system).

If 12V is suspect weak, you can always "jump start" the 12V in the trunk from another car. Just make sure you hook up cables correct polarity....and leave the other car off. No need to have it running.

 

Good catch, I hadn't thought of that. There's an easy way to confirm: watch the red security LED next to the sound system. When you insert the key in the ignition, the LED should either go out immediately (if it's a master key), or light solid for a couple seconds, then go out (if it's a sub key). Either a master or a sub ought to be able to start the car. If the LED does neither of those two things, then that key won't start the car.

-Chap

 

!!!
that doesn't help anybody help you....

• what wire? color/location?
• what reasons led you to try disconnecting that exact wire?
• you got no starting click when it was connected, but you do after disconnecting it?
• any different dash lights/other effects?
• anything else you've connected, disconnected, or changed?

Sure you can get your hands on a scan tool. There are some other threads here that describe a bunch of different choices.

Be safe....

-Chap

 

Not really likely, reseat the connectors at the traction battery on the left rear. Also the connectors to the hybrid vehicle ECU found under the passenger side, floorboard.

The codes suggest a chassis wiring problem between the engine ECU located under the passenger-side floor board to the traction battery ECU in the rear. We're hoping nothing inside the traction battery case as that is a pain to take out and inspect.

Please take pictures and share.

Bob Wilson

 

Don't sweat the C1259. That's just the brake ECU saying "uh, HV ECU told me something's not right." After the other stuff's fixed, the C1259 can be cleared.

The C1253 could be one of several things funky in how the brake ECU turns on and off the pump that boosts up the brake fluid pressure. This is the pump that makes the occasional 'growwwwwwwll-CLICK' that you'll hear from under the hood after braking several times, or right after turning the key on. By the way, are you hearing that sound at all when you turn the key ON?

This is a problem, but not your chief problem, so it can be put off until after you find why the car won't ready on.

P3105 is a problem with communication between the battery ECU and the HV ECU (under the carpet at the passenger's feet). This is a two-wire communication circuit.

Your translation for P3030 doesn't match what's in my manual - where did it come from? In my book, P3030 is a break in (at least) one of the voltage-detect lines in the traction battery forward busbar module. That will probably require an eventual foray into the battery case to sort it out. But it also can probably wait until the more serious comm issue is dealt with.

Bob asked about rodents. I'll ask, where has this Prius been stored, in what temps/humidity? Any salt air?

You'll probably want to sign up at techinfo.toyota.com for at least the $15 (last I checked) two-day subscription, and download from the wiring diagram manual and the service manual volume 1, starting with pages DI-238 to 239 (for P3105), DI-341 to 343 (for P3030), and DI-416 to 420 (for the brake booster motor).

In the wiring diagram manual, besides the specific system circuits in section H, you'll also notice that section G shows you how all the wiring is routed. I.e. where the circuit diagram shows you that the HV ECU to battery ECU comm wires leave the HV ECU at connector H13, cross from the instrument-panel wire harness to the floor wire harness at junction connector IF2, and reach the battery ECU at connector B17, it will be section G that shows you exactly where in the car these things happen and what the connectors look like (pp. 37, 38, 42, 43).

Before digging out any actual wires from under the carpet to check for tooth marks, etc., it makes sense to visit these connectors and check for corrosion, contact resistance, etc. You can unhook all the connectors and ohm out the wires between the corresponding pins, and get an idea what wires you'll have to dig out if any (and if the problem wasn't just bad contact at the connectors themselves).

Good luck!
-Chap

by the way, my edition of the manuals shows an interesting mixup: the brake ECU terminals known as MR1 and R1+ connect to the relay known as Hydro Motor Relay 2, and MR2/R2+ connect to Hydro Motor Relay 1. The wiring diagram manual agrees (both in sections H and M), so I haven't checked on the car itself but it might be a real thing (as in, the guys who make the relay-names label on the box cover got them swapped, or something); don't get taken by surprise. But that brake issue is for later, anyway.

 

I think Alexandria could be a warm, moist, and possibly salty place for a car to sit for three summer months. An oxide layer on connector pins thick enough to impair the connection doesn't have to be visible to the eye. Sometimes just unplugging and replugging the affected connectors (a few times if need be) can be enough to make good contact again. If an electronics shop near you has contact cleaners like GC Jiffy Bath, you can unplug connectors, spray them lightly, then replug them a couple of times. But even without cleaner, just the act of unplugging and replugging, as Bob suggested earlier, can help.

I would try this with at least the connectors B17 (at the battery), IF2 (near the driver's kick panel), and H13 (at the HV ECU under the passenger's carpet). Be sure to find the right connectors: when you say "wire coming up through the floor board" that could be, for example, the downstream oxygen sensor, not anything you're looking for. The pages I mentioned out of the wiring diagram in my last post will show you just where B17, IF2, and H13 are and what they look like, so you'll know them when you find them.

Just replugging the connectors themselves might solve your problem then and there. If not, you might have to go further and pin down a problem somewhere else in the two-wire comm circuit between the HV and battery ECUs. It might be in the wires between H13 and IF2, or the wires between IF2 and B17 (or in either the HV or battery ECU itself, but we won't go there unless we have to). Do you have access to/know how to use an ohmmeter?

In case you end up needing to physically look at the wires, those same pages in the wiring diagram manual will show you what routing they follow in the car, and their color codes, so you'll be able to find them.

Once you've nailed the no-start problem, you'll be able to start on your brake pump issue, and if oxidized contacts were part of the first problem, the same techniques might help there too. Once you've seen how the manual showed you where to look and what for with the first problem, you'll know how to look up the connectors involved in the brake pump circuit too.

Happy hunting!
-Chap

 

You found IF2 by the looks of it - one of the junctions in the comm link between the HV and battery ECUs. I was mistaken earlier saying that's a two-wire link; it's two each way, which accounts for all four of those wires plus the shield braid.

Now might be a good time to break out your code scanner again and see if you changed anything. If you've been pulling a lot of connectors besides the three in this circuit, it's possible there are new codes that aren't really connected to the problem, so it might also help to clear first, then see what codes come back.

This can go faster once you've downloaded the info and you're able to say what connectors and circuits you're looking at, and we can be on the same page. Till then, I'm sure you'll still find plenty of help on here but I'll have to bow out - things to fix on my own car!

Good luck,
-Chap