Need help, reversed polarity installing new aux battery

For a number of the more-important relays in the car, the ECUs monitor whether they are stuck. They compare the downstream voltage when the relay is being energized and not, and set codes if the state doesn't change accordingly. So, as with so many things, it's an easy question to answer once you are able to talk to the ECUs.

 

Too bad he cant.

Check fuse
ECU B
ECU IG
Those protect the Gateway ECU. The OBD port talks directly to the Gateway ECU.

It could be the Power Source ECU
Gateway ECU
Immobilizer ECU
Hybrid Vehicle ECU

I assume you have checked every single fuse in the car with an ohmmeter? Engine bay & cabin?

Based on how many of these I have seen in the last 13 years on this site its probably the Inverter. Those are pretty cheap now. Lots of them around.

 

I'm almost certain I have not seen that in a car. I'm not sure a car would last long enough for a relay to do that. The ones I saw stick operated several hundred times a minute, 24/7 for several years.

 

Take the fuses out and probe each leg socket make sure your on the B+ side of the fuse when checking.

Stop grasping at ECU's you have alot more to check.

 

Deleted

 

If you, or anyone else needs the maintenance manual for a Gen 2 Prius, I can make it available. Just PM me with a request and I'll give you a link to my copy. Make sure to tell me if your Prius is a 2004-2005 or a 2006-2009 as the manuals have slight differences (I have both versions).

I never found copies of the Gen3 or Gen4 maintenance manuals so we seem to be stuck with paying Toyota to download sections of those manuals.

JeffD

 

Something occurs to me. Ed has suggested the reverse-polarity incident may have damaged the inverter (most likely the DC/DC converter, which is one part of that assembly). There is also this issue of being unable to establish communication with the car's ECUs. Converter damage by itself doesn't explain that (unless the converter was damaged in such a way that it continues to short or load down the 12 volt system).

As there's been another recent thread where the exact needed connections were discussed, there's a way to get the converter temporarily out of the picture, and focus on whatever problems may be left in the power distribution system, and maybe get back to a point where the ECUs can talk.



You can isolate by unbolting the fat white wire at position 3E of unit A in the underhood fusebox:



With that wire unbolted (and wrapped in something insulated so it doesn't go flopping against random metal car bits), you have the converter, which may or may not be blown, removed from the 12 volt picture. Everything else is still connected to your 12 volt battery, and with a good charged battery there, you should have 12 volts everywhere 12 volts should be, or be able to track down what is open if you don't.

With 12 volts everywhere 12 volts should be, you ought to be able to communicate with the ECUs. Or with some of the ECUs and not with others, and you can also start narrowing that down. The "multiplex communication" section in the manual gives an overview of the different communication networks in the car and which ECUs are on which ones.

 

It seems to me, if the clock is one of several things you know of that aren't working, I'd almost rather start by just sitting in a comfy chair with a pencil and making a list of those things. Then stay in the chair, with the wiring diagram open and a fresh sheet of paper, and turn that list into a circuit tree. You will still eventually be back out at the car with a meter, but the pencil in the comfy chair is where you'll decide what you're going to do with that meter when you go back out: what specific questions you need answered, and which one will be answered by each move you'll make with the meter.

 

You're basically going to need an oscilloscope to see what's going on. The reverse polarity can kill basically anything in the car. Most of the circuits have protection, but a reverse polarity event is not something common in a car. It's designed for short inductive spikes driving the 12v bus potentially negative with the battery removed from the vehicle and the alternator stopping. In the Prius obviously you don't have an alternator but automotive design spec's still apply.

The OBDII connector is not a monolith. I've seen you ask a few times why you can have power but no signal. It sounds like something is dead dead dead and pulling the CANBus to an invalid state. The CANBus if you aren't familiar is like a party line. 2 wires that go to all the ECUs in the car. And when one of them wants to communicate it waits for the bus to be idle then bursts some information that another ECU (or a subset or all ECUs) listens to and perhaps acknowledges. Then it gets off the bus making it idle and another ECU can try. If you have a "stuck bus" this is where one or both lines are stuck in a permanent low or high state due to physical damage and the bus never looks idle. Nobody communicates. Nothing can happen. There is really no way to find the culprit other than hunting for it one-by-one. You can do a binary search where you can split the bus in spots and see what each side of the bus looks like. Ideally 1 will be back to normal and 1 won't be. Now you've eliminated half the suspects. Then split the half of the half that is still broken, etc.

To me that's the first thing that needs to be done. Without ECU communication, nothing is going to work.

My favourite is in my DeLorean, the "RPM Relay". It does like 3 things, but one of them is taking in the tachometer signal (pulsed) and averaging it through a cap to turn a transistor on or off to turn the relay on or off to the fuel pump. This is great until the cap degrades a bit over time and then the average idle RPM signal is too low to keep it on fully and the relay just clicks itself to death soon stranding you on the side of the road with no working fuel pump.

 

What makes it even more fun is in a Gen 2 Prius has three networks, one CAN, one BEAN, one AVC-LAN, one "gateway ECU" that connects to all three. CAN is an ISO standard, BEAN and AVC-LAN are both Toyota specials. The CAN in Gen 2 has a multi-star topology, the BEAN is a ring, and the AVC-LAN is a star with the MFD at the center. The "multiplex communication" section in the docs has the details and which of the ECUs sit on which networks and where. That's important for deciding which items you might want to isolate from what while you are troubleshooting, and what exactly you would learn from isolating each one. Without those details, it will all start swimming in front of you.

 

I was thinking about the oscope the whole time as you must be able to see that signature is it distorted is it low is it gone but the op is no wheres near that. I would hang a scope on that Can rail and see if anything I do as I go along creates a little buss com. Right now its flat line.

I think and I may be wrong but on the Can system if one ecu goes offline the com rail fails. The gateway stops talking. A scope would prove me wrong.

The Inverter is a big part of the com rail and the main power source. Remember the Inverter Battery B+ sensing line that's attached to the battery assy got a reverse voltage slam too directly to the Inverter dc-dc current control section. And wasn't a jumper with a few sparks he went and turned on the lights
because it was bolted in backwards lol...Ouchy Ouch....

I have owned maybe 20 scopes in my life mostly tektronix's down now to just 2 a Fluke 123 that I beat up and my favorite all time I love it because unlike Tek scopes it has an excellent trigger circuit.
They will bury me with this bought brand new 35 year old scope lol:

Sencore SC3100 Automatic Waveform Lot P220 | eBay

 

I'm willing to believe the converter may be damaged, but it doesn't sit on any of those three networks, the CAN, the BEAN, or the AVC-LAN. It has its own separately-wired private line to the HV ECU and that's it (well, along with the one IDH wire it uses to tell the HVAC "please turn off the electric heat, I'm overloaded").

If a person wanted it completely out of the picture, besides unbolting the fat white wire aforementioned, just unplug connectors C5 and I10. Then at least one can start to attempt conversations with the various ECUs in the car and see who responds, or look for causes unrelated to the converter or inverter until some of them start responding.

If you do get to start a conversation with the HV ECU under those conditions, of course it's going to complain that it can't feel the inverter. But that's fine progress; the homework is to get to that point.