Potential short circuit maybe in the CAN bus

I purchased a 2008 prius at an auction that had issues that were not defined. The lights on the dash were:
ABS,VSC,(!),SLIP Indicator Light (car swerving icon),check engine icon

I bought the mini vci that came with Techstream software (version 10.00.028) and I ran it initially and found these codes:

C1241
C1378
C1203
C1345
C1392

I believe there is a short circuit somewhere that is making the auxiliary battery go to a low voltage after only a few minutes of testing. After I charge it with the Optima charger (recommended on priuschat) it is 13.2 volts and when the ready light is on (and the engine starts) the display shows that the HV is charging and when I attach a voltmeter to the auxiliary battery it goes up to 13.9 volts. But after about 5 minutes of running and I shut it off and the try to turn it on the ready light will not come on again and the aux battery is down to 11.5 volts. The battery was tested at a local auto parts store and they said it was fine, in fact I have an addition battery that someone gave me and it was shown to be good as well but they both go down in voltage after turning on the prius.

I bought a used Skid Control ECU on ebay (because of the C1203 code) and installed it (very difficult) but after that there were no warnings on the display and I drove it with no issues.

Then I ran Techstream again and did a system check and it come up with:

U0121
B1421
B1794
B1650
B1660

That looked good but then I ran the "CAN bus check" because I thought there might still be a short (thinking it was on the CAN bus) and then all the entries (e.g. ECM (Engine), HV Battery) stayed red (= No longer communicating on the CAN BUS).

And also all of the lights that were on before replacing Skid Control Unit went on again:
ABS,VSC,(!),SLIP Indicator Light (car swerving icon),check engine icon

I ran the CAN bus check when the Ready light was on and read somewhere that you shouldn't do that so maybe that is was did the damage to either the CAN bus or the ECU's connected to it. Now I can not even get the ready light to go on.

Anyway I have been using pdf documents that show how to track down potential short circuits but I found different values for ohms. When I measure the resistance between CANH and the Battery + using the OBD connector I get about 8K ohms but one document I have says it should be more than 1M ohm and the other says it should be more than 6K ohms (see attached screen shots).

Has anyone every measured the resistance between pin 6 and pin 16 on the OBD connector? If so what was the resistance?
At least it will help me direct my attention in the right direction. I have tried measuring the resistance after disconnecting all of the ECU's one at a time to see if one of them was causing the potential short circuit but there was no significant change.

Thanks for your help!
Tim

 

Thank you all for your suggestions!

It makes sense that a short in the CAN bus would not be enough to drain the battery, so I will not look for shorts in the CAN bus anymore, good tip.

I wanted to confirm some volt/amp measurements that I had done in the past so last night I ran them.
I bought a bayite DC 6.5-100V 0-100A LCD on amazon and have been using for some time it but I am not sure how accurate it is, any thought on this?
In the past if I pressed the brake pedal and hit the power button the current meter would start flashing, I am guessing that is was above the 100 amp limit of the meter.

So I did some tests last night.
When I pushed the button twice (w/o brake), there was clicking coming from the engine, when I heard the clicking sound the amps would go up to over 20 but when it stopped the amps would go down to about 8 but after some time it stopped clicking.

Here are the results:
Power button Volts Amps
off 12.7 .86 with key inserted, w/o key .00? (meter only has 2 digits)
push once 12.6 1.38
push twice 12.3 8

I am charging my new optima battery (using the optima charger) now and will install it soon and run the tests again because I ran techstream and got the code C1241 (and C1242) and I also had the red triangle when I did these tests. It looks like this battery is too low so I don't know if it causes some of the other error codes I got:
U0100, U0293, U0123, U0124, U0273, B1650, B1660.

But it did do something that I have not see before which is when I stepped on the brake and hit the power button, the ready light would go on and the engine would start but then after a few second both would stop. I am hoping it is just because of the low battery.

As for the brakes, I have driven it a few times. I drove it from the auction but we had to have a second aux battery connected with jumper cables to the main aux battery. I don't remember having any brake problems but I should probably have them inspected, and probably should take it to the local dealer for a complete techstream test. I didn't know anything about toyota-com-owners, thanks for that tip!

Patrick, I believe in the past when I was able to get the engine running for some time the voltage on the aux battery was 13.9 volts but I am not sure so hopefully I'll be able to get the engine running again and then I'll run it for awhile and monitor the voltage.

I also think the test of pulling the fuses and checking the current will be a good one.

Thanks all, will post some new results soon.
Tim

 

Well, I have to thank everyone for the progress I made today, I think the main problem was the aux battery (although I am not 100% convinced yet). I put in the charged Optima and had some issues with lights on the dash but was able to resolve them (I hope it is permanent). The red triangle was there I believe because I had forgotten to reconnect a relay on the side of the drivers side junction box (no 90987-02027), not sure what it is for since they don't show it on the diagrams (just the 3 in the front). I cleared the other ones by putting a jumper btw pins 4 and 13 on the OBD connector and hitting the brake 8 times. The voltage of the aux battery stayed around 12.9 volts even after running it for about 5 minutes and when it was running it was between 13.7 and 13.8. The current was the same as it was in my last post but the meter did flash for a little bit when the Ready light went on and then came back showing 0 amps, is that correct?

The interesting part of all of this is that I went to the toyota site /owners (I can't upload my comments where there is a url in it) and found out that it was taken to a dealer in May of last year. I called the dealer and they looked up the repair order number and told me that the car was towed there because it wouldn't start and they diagnosed the problem as an unknown fluid in the inverter and the recommendation was to replace the inverter. The owner decided against it and I assume that is when they donated it to the non profit organization where I bought it. That makes me a little nervous taking the Prius in for a techstream check since obviously the car will start. I would also like to get the brakes checked since I replaced the skid control ECU, is there a good site to find recommendations for garage's that work on Priuses? I live in Albuquerque, but have many friends in San Francisco, and so would like to take it to the Luscious garage there but not sure if it will make it that far (it has about 167,000 miles on it) and again not sure if it doesn't have an major problems. Like fluid in the inverter, does that mean I have to take off the lid of the inverter?

Thanks again to all of you, without your help I would probably still be trying to find a short somewhere!
Tim

 

Last night everything looked good, the engine came on, there were no lights on the dash and the voltage showed 13.8 when the display showed the battery being charged, in addition no error codes showed up when I ran the techstream diag. Afterwards I disconnected the battery just in case, and it showed 12.9 volts.

This morning (thinking I would be able to drive it) I put most of the things back together that I had taken off to do measurements of resistance, like the dash components, glove compartment, etc, reconnected the battery (the new Optima), and then tried to start it but without success.

The Ready light won't come on, and I get these lights on the dash:
ABS, Check engine, big red explanation point, tire pressure.

the volt/amp measurements are these:

off 12.7V
push once 12.2V 6 amps
push twice 12.2V 9.8 amps

Techstream now shows C1241, U0073, U0123, U0124, U0126, U0293, B1650, B1660. Since C1241 means a low battery, does that mean that 12.2V is too low? And since this is a new battery does it mean that too much current is being drawn (i.e. a short somewhere)?

The other thing that happens is if I press on the brake (after pushing the power button twice). I hear clicking in the engine compartment (inverter?), and the amps goes up to about 23 and the display goes dark and then comes back on. It shows P/S in red and sometimes the hybrid system warning light (sometimes it is off), see attached photo. Sometimes when I step on the brake I hear a fan go on in the engine compartment, maybe the same one that goes on when the engine starts, I am not sure but the amps go up to about 28. Also sometimes the gear display (P,R,N,D,,) flashes (see attached photo).

It seems like Patrick was on to something when he mentioned and intermittent wiring harness issue. I wonder if the other reason might be the inverter with an "unknown fluid", could that be causing a short?

When the problems are intermittent solving them becomes very complicated!

Thanks again for your insight into these issues.

Tim

 

Thanks Patrick for your suggestions. I disconnected everything and put it back to the state it was in when everything was working but now I can not get the Ready light to come on and the Red Triangle does not go away. I did some measurements of the voltages and ohms on the connectors on the skid control ecu based on the page I uploaded an image of and all the voltages were above 11 and all the ohms were below 1. I also checked the voltage on the connector to the brake control system and it was also above 11v (pin 5 to GND), I also attached a screen shot of that test.

I played around with the wiring harness next to the skid control ecu but that didn't help. I keep rotating the 2 good batteries I have after charging them so the one in there now shows over 13v when nothing is connected. The more tests I do the lower it goes (especially if the engine fan goes on) so I don't want it to be a factor in my testing.

I also ran health check again and got the same codes but this time C1242 showed up.

Any ideas on what kinds of things I can try now? I am at a complete loss, especially since this is so intermittent.

Thanks again,
Tim

 

Yes I have 3 skid control ecu's the orignal and 2 I bought on ebay (I thought I destroyed the first one when I ran the CAN bus check with techstream, which caused the ABS and VSC lights to go on). I connected up the original SK ECU and got the same results.

I hear clicking in the engine compartment when I press on the brake (w/o pushing the power button). I removed both of the ABS relays and the clicking noise stopped and then I inserted one at a time and found that they both click when I push on the brake. Is that normal? Maybe I should just replace them and see. Thanks for your tip because I did not know what the cause of the clicking noise was, now I do!

I did try tapping on both of them with no results.

Thanks again!
Tim

 

Thanks Patrick,

I ordered 2 ABS relays on ebay (total $14) so will try them when they arrive. But something interesting happened yesterday. For some reason the radiator fan is going on when in IG-ON mode (this just started), and the current being drawn would jump up to 27 amps, I wanted to stop that while I am doing the testing with techstream so that the battery would last longer. I found out that the relay for the fan is in the Unit C box. One thing I noticed is that the Unit B box is upside down (see attached photo), and I don't know if the cables will allow be to reverse it. The other thing is when I disconnected one of the connectors in Unit C, the red triangle no longer came on in IG-ON mode and it reappeared when I reconnected it.

Does this make sense? Does this give a clue as to why the red triangle is coming on?

Getting an error when I try to upload the picture of Unit B, C. The label of Unit C is toward the driver's side while for Unit B it is toward the front bumper.

Thanks,
Tim

 

Thanks Patrick,

I got the 2 ABS relays yesterday and I tried them out but no changes, but it was worth eliminating some possibilities since there seem to be so many. I tried using all of the buttons on the steering wheel to make sure no air was being sent to the cabin, and what I noticed was different icons lighting up on the dash (e.g. A/C) and I made sure that none of them were on but the radiator fan still comes on so I might be missing other possibilities since I have never used those features. Also I disconnected all of the connectors in Unit B and C and the radiator fan still comes on. The only exception is for the connector for the 2 15A fuses (IG2 relay, EFI M relay), when I disconnect that none of the dash lights come on. Don't understand how the fan can come on without the Fan No. 1 relay connected, unless there is something wrong with the wiring.

I have been rotating batteries (charging them with the Optima charger) for quite some time, swapping them when the voltage gets below 12.4 volts so that I can be sure it is not a battery issue. Both of the batteries (one is Optima) are over 13 volts after charging.

The behavior of the car now is something I have not seen before, when I go to IG-ON the lights on the dash go on and off 3 times before they stay on, during that time there is a clicking sound coming from the engine room.

I believe I misstated which connector caused the red triangle light to stop going on, but now I just have to remove the 20A HEV fuse from Unit B to make it so the red triangle light does not come on. I will keep investigating this and let you know if I find out anything.

This car is a real challenge since the behavior keeps changing but I really appreciate all the feedback!

Tim