Help ICE wont start, Comm buss Down after Cat stolen/replaced

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Douglas88, Jul 28, 2021.

  1. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    My 2005 prius had the Cat stolen. Drove it 20 miles to repair shop ok....but did not have it repaired after got estimate. Then 2 miles home and entire Gas gauge bar was flashing on and off all the way home. Parked it outside. Later drove it into garage and entire gas bar was still flashing, AND red triangle was now on, along with abs, vsc, traction, brake lights. I assumed it was just cus the O2 sensor and cat were gone. I jacked up one side, replaced the O2 and cat. Took it down, and all the above lights were still on. Took it down the road 1/4 mile, realized ICE engine was not coming on, turned around, and ran out of power. Synergy drive had now disengaged. All above lights on and red turtle energy monitor light on in lower display. 12 volt battery was also going dead, as it had mostly discharged while I was working on car with hatch open earlier. Had to jump 12 volt to get car to go into neutral and then pulled it 1000 feet home.
    Charged 12 volt up, put 5 gal of gas in the car after reading it takes 3 gal if you run out before car will start ICE motor, for it was low on gas all this time as one bar was flashing before any trouble started and cat was stolen. CAR will STILL not start ICE. Used Torque . IT says no communication with ECU, Buss is down. Fault Code "U0100 Data bus ECM no communication" No other fault codes. I then used Dr. prius, IT says battery is at 24% 212 volts, 7.59 cell voltage, .05 voltage differences. No communication with ECU... Error codes are POAA4, CC100, CEOAA, P1300.
    I have used Torque app and Dr Prius to reset codes, and disconnected 12 volt battery, and orange drive battery cut off switch, for 30 min after resting codes. NO change. Same codes, same messages about no communication, ICE will still not start. All the above lights are on and entire fuel gauge bar is still flashing. I have no idea why red triangle came on in first place, but had at first thought it was because of no cat or O2 sensor. I speculate that Maybe during the repairs, jacking up one side of car pretty high, with the tilt, it felt it was out of gas and that is why ICE did not start after the cat repair? I have no idea. Please help. I have no idea were to go from here. ??? PS. Just did Torque again to get a screenshot and now it also shows POAA4 powertrain code, along with U0100 from before . Here is short video of how it all looks when I turn the car on.
    And am attaching screen shot of Dr. Prius. and Torque display.

    Please help, what can I try next? THANK YOU
     

    Attached Files:

  2. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    6,543
    2,755
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    If you didn't tape up those loose 02 sensor wires they could of been blown around under the car when driving and caused a short that fried your ECU. This has been mentioned on here a few times as a problem people have had because they didn't know the wires could short out.
     
  3. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Well I sure hope not, I would not have thought that could happen, good to know for the future. Do you think if it had, that the car would have kept running? I guess more important any ideas on how I could check if the ECU is ok? Further I guess a replacement salvage ECU would have to be programmed by the dealer before installation too? Thank you for the idea...though I hope this did not happen. hope it will prove to be something else....
     
  4. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    1,207
    499
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    You unfortunately do not have adequate tooling to try and diagnose this. Torque app is "better than nothing" but you have to have a scanner that is OE level so that you can be sure that you are scanning all the control ecu's on the car and that whatever codes you pull are correct. Several codes that were posted earlier don't come up at all for a 05 Prius- which means if the app is "lying" to you, then when should you believe what it tells is correct?
    Many here get a mini VCI cable from amazon or ebay (usually comes with a bootleg copy of Techstream - toyota's diagnostic software. It can be a bit fiddly to install it on an old windows laptop but it is worth it.

    Also use the search feature on the forum to see what it takes to find a copy of the factory service manual.

    Now one thing you can try is to test ALL the fuses on the car to see if any are bad. But do not try and start or drive the car until you correct the loss of comm fault- your battery is near the point of not being able to start the engine. The engine ecu is "behind" the lower glovebox and you need the wiring diagrams to check for good powers, grounds, and comm lines while the ignition switch is on (you will want to use a battery charger to keep the 12V power up while you do testing.)

    The engine ecu is quite cheap on ebay (which is plug and play on a Gen2)- find one that matches the number on yours (FYI, for testing you don't necessarily have remove the old unit, there is JUST enough slack in the wiring to flip the four connectors around and plug in the replacement - which can just "dangle" while you can see if it helps).
    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Jul 29, 2021
    Last edited: Jul 29, 2021
  5. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    6,543
    2,755
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Seems to me your symptoms: Fault Code "U0100 Data bus ECM no communication" point to a a fried system. When you keep driving a car that's damaged you can cause more damage.
     
  6. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    THank you much! to all who have replied! I ordered the VCI cable and techstream as you suggested....so I will be able to do more detailed testing. I found no bad fuses, all seem to be OK. I also found that in torque in settings it claims it is indeed not communicating with ECU. I found a place that said to check the communication circuit by using a DVOM to read resistance between diagnostic port connection terminals 6 and 14, and if it is 60 ohms that is good. I did this and it is 60 ohms. I am adding images about this now.

    I wonder if anyone has any comment on the other code that is coming back POAA4 "Hybrid Battery contractor circuit stuck closed" I have the drive battery open already, is there a place I could meter to see if this relay is really stuck open or if it is a communication issue giving this code? IF so can someone advise me were to meter and what to look for?

    I also got some sort of a PDF manual, but it is too complex for me to identify just what connections to meter to see if ECU is getting ground and power. Nothing happened to the car that should have created such a physical issue. If there is anyone who knows what wires to meter and what to look for, I think I can find the wires and test this?

    Sounds like to me the consensus, as I understand it, is that perhaps I could buy a used ECM and try it. IS that a correct assessment of a good thing to try??? And if I do, and plug it is while leaving the old one in, do I need to ground it?? OR do the connectors take care of that?

    Thank all for assistance again...
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    1,207
    499
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    Well, the resistance test on the CAN bus is good. Since there are two terminating resistors (one 120 ohm in the ECM and one 120 ohm in the battery ecu- in parallel = 60 ohm) it means that the network wiring is intact - to the ECM. No comm fault is gotta be missing power , ground, or damaged ECM. Will see if I can go over diagrams later.
    I wouldn't worry about the P0AA4 until you have techstream working (so you can confirm that it's correct) and you fix the ECM problem (because a contactor doesn't matter if the ICE can't run).
    If you get an ECM ($20-40 from ebay, why not?) then you can just plug it in, it (should) be grounded through the wiring, not the case.

    Posted via the PriusChat mobile app.
     
  8. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    6,543
    2,755
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    yep... if a wrecker has a prius near you and you can easily go pull the ECM for cheap that's probably the fastest way to get back to focusing on fixing the rest of the cat theft mess.
     
  9. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Thank you, I am not driving it, could not if I wanted to. By fried, I think you mean, ECU is toasted. I am planning on trying a new one. Do you know if I have to do something to get a new ECU to recognize my keys?
     
  10. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Thank you very much. THis post is helpful! Helps me know what is important and direction I need to take next. I am going to get a replacement ECM and try it...seems like the next step while I wait for my techstream stuff to arrive. Do you know if, a new ECM will require me to reprogram my keys, or if they will still work?
     
  11. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    5,872
    3,123
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    The fobs will work as the ECM does not handle that. That job is done by the immobilizer ECU. The ECM is plug-n-play.
     
  12. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Yea. I recieved my tech stream and got it installed and working. I hooked up to the car and tried to access the Engine ecu. It said "selected system is not responding or is not available Please check the repair manual for applicable systems" So I checked the HV battery system live for codes and it said "code U0100 lost communication with the ECM/PCM "A" " SO is there anything else to do, or to check now that I have the techstream up and working, (per above suggestions to get TS for deeper diagnosis someplace above) or is it time to replace the ECU? Also is there a good place to learn about how to better use this TS tool...pretty cool! and as always...thank you!
     
  13. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    5,872
    3,123
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    Do a "Health Check" from the main screen. This will interrogate all the ECUs and report all DTCs found.
     
  14. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Thank you, I would love to do this, but I do not see that option. I am attatching a picture file of what I see on my main techstreem screen. I can not find health check in the menus or on screen, can you guide me as to how to get to this choice please?
     

    Attached Files:

  15. mr_guy_mann

    mr_guy_mann Senior Member

    Joined:
    Sep 3, 2020
    1,207
    499
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    The "health check" button isn't there on your installation. On some installs, the "patch" that allows the program to work has a side effect of removing health check. So you would have to manually check codes on every system in your car to see if there are any other comm problems.
    If it turns out that only the engine computer isn't talking, it's up to you whether you want to get a used ECM and try that or do you want to test for powers and grounds to the ECM.

    Posted via the PriusChat mobile app.
     
  16. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    5,872
    3,123
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    As mr_guy_mann said above, it appears the Health Check Button is absent from your System Selection Menu screen.

    TS System Selection Menu Health Check.JPG
     
    #16 dolj, Aug 4, 2021
    Last edited: Aug 4, 2021
  17. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    15,199
    10,578
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
  18. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    OK thank you much, as well as the poster below. I checked other modals and they are working. I would love to check the ground and power voltage to the ECU if anyone can tell me which pins on which connector and what voltages to look for I would appreciate that guidance.
     
  19. Douglas88

    Douglas88 Junior Member

    Joined:
    Jul 26, 2018
    30
    4
    0
    Location:
    missouri
    Vehicle:
    2005 Prius
    Model:
    Two
    Well I went ahead and got another ECU and put it in. The car acts excatly as before... Red triangle, yellow lights, red turtle, etc...says "problom" for a moment on power up, will not engage into nutral, or drive or reverse, or start engine. Dr Prius and torque both say codes PoAA4 and U0100 power bus issue...no ECU communication. ANY IDEAS on what to try next??? Measure the power and ground wires to ECU?? IF so does anyone know what wires and what voltages to look for?? Other ideas?? Reminder that above I checked this circit resistance and it was good...and this was suggested...."Well, the resistance test on the CAN bus is good. Since there are two terminating resistors (one 120 ohm in the ECM and one 120 ohm in the battery ecu- in parallel = 60 ohm) it means that the network wiring is intact - to the ECM. No comm fault is gotta be missing power , ground, or damaged ECM. Will see if I can go over diagrams later." Can anyone help me with checking the power and ground lines??? or other ideas?? I can not imagine what happened to cause this problem to happen. THank you to all in advance!!
     
  20. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
    5,872
    3,123
    0
    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    The repair manual advises if you have another DTCs in addition to a CAN communications DTC, fix the CAN communications error first.

    For CAN comms errors it is advisable to get the repair manual as the diagnostics are involved and the procedure links multiple sections of the repair manual so it can't practically be conveyed via a forum thread.

    You can find more info here and here.

    The following links provide examples of the type of information for a 2004 Gen 2 Prius and what might be involved with the U0100:

    U0100/211,212 | Lost Communication With ECM/PCM ”A”
    U0100 | Lost Communication With ECM/PCM ”A”

    Keep us updated.
     
    #20 dolj, Aug 5, 2021
    Last edited: Aug 5, 2021
Loading...