P1636 and P3002 - Prius 1st Gen.

I wouldn't recommend opening the hv battery unless you have done some type of safety training. High voltage gloves are in every hybrid tech's tool box. That being said there are many members of this forum who have opened these batteries hundreds of times and may be able to describe how to do this work at home.

 

Unfortunately, the back seat has to be removed to get to the hybrid battery.

You know since yesterday, I have read several internet postings about this problem and quite a few times it turned out to be a bad 12v power or a loose connection on the 12V battery. I know you have checked battery voltage but have you really (and I mean really) conducted a close inspection of the 12V battery connections (including the one that hooks to the body of the car (negative strap))? If I were in your shoes, before taking apart the whole car, I would inspect, clean and tighten all 12V connections.

 

Sorry about the delay, family medical, but the regular posters are excellent skilled folks and we regularly back each other up. I am glad you got a good reading on those voltages . . . the first set were impossibly high . . . boiling battery acid high.

Techstream is the gold standard but I understand pricy. Next would be AutoEnginenuity which I used. But now I use a Chinese knock-off, miniScanner. It is cheap but buggy, record for 3 minutes and requires manual buffer save and recording restart. Long enough to get useful diag but not for engineering studies. We tried to go over the options in the sticky.

Bob Wilson

 

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I hope I'll be taken in the right spirit if I say this is a good example of why not to say "my manual does not show" something unless the manual you're talking about is the real one. Sure, I have used Haynes/Chilton/Clymer sorts of books before, say if somebody wanted me to look at their car and it was all they had (but even there, I'm getting more and more likely to tell a friend "sure, I'll be happy to take a look if you've got the shop manual for it". The fakebooks are so often such a waste of time).

P1636 is listed on page DI-18, and P3002 on DI-320 (these page numbers are from my 2001 book, might be different for 2003). The troubleshooting steps for them are on DI-146 and DI-326. The C1213 that was pulled later is listed on page DI-358 with the troubleshooting info on DI-384.

Basically, these codes come from three different computers in the car (the engine control module, battery ECU, and brake ECU) all saying that they are failing to communicate with one other computer, the HV ECU.

The troubleshooting pages all show simplified wiring diagrams for the communication circuits involved, in case you wanted to check for simple connection problems, but the "hint" on page DI-326 does say "If HV communication errors are stored in [more than] one ECU, replace the HV ECU." Here there are three other ECUs all pointing metaphorical fingers at it.

There haven't been any codes here that have anything to do with tearing into the HV battery. The 12 V aux battery voltage was worth checking, since the first reading was weirdly high and the ECUs do operate on the 12 V supply, but the later reading showed normal readings there, so that seems not to be the culprit. At this point I would certainly dig out the HV ECU (under carpet in the passenger footwell) and check the connections to it. If the connectors are loose or corroded (water getting into passenger footwell?) or there could be anything wrong at the communication circuit connections (connector H14 pins 17, 18, 19, 20, 29, or 30, or H13 pins 2 or 20), maybe there's a low-tech fix, or if there's a visible or measurable problem at the 12 V power and ground connections (check the wiring diagram), but otherwise it looks a lot like a replacement HV ECU is in the cards.

Don't forget that after replacing the HV ECU, the ignition has to be left ON for half an hour without attempting to start, for the immobiliser ECU to accept the changed HV ECU and allow the car to start (BE-103). It might be worth putting a 12V charger on the aux battery if there's any doubt of it lasting half an hour of ig-ON. Losing voltage in the middle of the HV-immobiliser handshake might not be good.

Best way to use "I don't have the shop manual" in a sentence: "I don't have the shop manual, so I'm going to techinfo.toyota.com now to get it (or helminc.com for a paper copy)."

-Chap

 

Hmm, well, those are data communication circuits, but I wasn't really suggesting to break out your mad oscilloscope skillz. My first ideas were a lot more basic: is the HV ECU sitting in a pool of rust-colored water by any chance? Have any of the connector pins morphed into green powder? Even a 21st century car can still have problems you might spot just by looking. We won't know until you roll the carpet back and find whatever you find.

Only if there's nothing you can tell by looking, and if popping in another HV ECU doesn't solve the problem in one swell foop, then it might be time to look harder. Your voltmeter probably does have a continuity test function. If you check the wiring diagram to find the connector/pin where the other wire end winds up from each pin I listed at the HV ECU, you could test each wire end-to-end for broken continuity. At least you could start with the ones that go to the engine control module, since it's easy to get to right behind the glove box. The brake ECU is harder to get to, and the battery ECU you might prefer to leave alone inside the HV battery case.

The wiring diagram manual has a section that shows exactly where in the car the different wire bundles are routed, and what connectors they go through on the way (it also has pictures where you can identify whatever connector you're looking at by color and shape). Since there seem to be problems with three different computers talking to the HV ECU, if the problem somehow turns out not to be the HV ECU itself, it might be smart to check the diagram for how far those three sets of wires travel together, before branching off to go their separate ways. The problem might be likeliest in that common portion. Small marks of mouse teeth, perhaps?

Sometimes the easiest way to learn something is to jump in. If you're unsure about how ready you are to understand the diagrams, you won't know until they're in front of you, and only then will you be able to see what makes sense and ask for help with what doesn't. Besides, you're trying to solve a car problem right now - why try to do it without the chief source of the information you might need?

-Chap

 

Hmm, sorry, our postings crossed. So no visible damage at the HV ECU, eh?

Can you get your hands on another one? That would be the simplest quickest next thing to try, and might just solve the problem then and there.

-Chap

 

There was an ECU change for cold weather starting but I don't remember if it was engine or HV.

Bob Wilson

 

Pretty sure it was the engine, not the HV, ECU, and the change amounted to an increase in the timeout
allowed for the engine to start before giving up and reporting a no-start.

-Chap

 

I am doing this from memory, not from walking out to the car and running the steps.

What codes, all of them, and the freeze frame does the car report now? - Start the car, connect the scanner, have it check each ECU and report the codes. In particular, HV, battery, and engine ECU and screen save the freeze frame. For now, I'm assuming you can make a screen snapshot to share. While doing this initial look, connect to the battery controller and read out the 19 module-pair voltages.

What codes return after clearing the codes? - Use the clear function to wipe out the codes. We then need to see what codes come back. Error codes are persistent so you want to see what is 'hard' versus ones that are transient.

Not that I remember.

Bob Wilson