Prius C water damaged ECU rebuild

Discussion in 'Prius c Technical Discussion' started by Prius city, Aug 29, 2021.

  1. Prius city

    Prius city New Member

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    Making progress with the water damaged Prius C rebuild. Any recommendations on next steps will be greatly appreciated. I now have no codes under hybrid control in techstream after I recently removed the hybrid battery and rebuilt the battery. I cleaned all the bus bars and swapped out the battery ecu (voltage sensing unit) and junction box assembly(where the 3 main relays are located). I then performed a grid charge of the hybrid battery and the hybrid battery is currently reading around 158 V after sitting for 2 weeks. Water damaged caused damage to the battery ECU (burn marks) but may not have caused long term damage the 20 hybrid battery modules. All 20 battery modules are reading approximately 7.9V each after sitting for 2 weeks.


    However still need to figure out how to correct the remaining codes so I can get the car in ready mode.


    Remaining codes are as follows:


    Engine and ECT


    U0293 - lost communication with hybrid vehicle control system


    P2118: Throttle actuator control motor current range performance


    P0102: Mass air flow circuit low


    P0113: intake Air Temperature circuit high input


    Air conditioning


    B1441 Air Mix Damper Control Servo Motor Circuit Passenger Side


    B1442 Air Inlet Damper Control Servo Motor Circuit


    B1443 Air Outlet Damper Control Servo Motor Circuit


    B14B2 Lost Communication with Front Panel LIN.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Umm, how water damaged?

    You might want to look at this post and the TSB it refers to, early in the process.
     
  3. Prius city

    Prius city New Member

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    • Chap thanks for taking time and providing the link to the post and the TSB it refers to. I have rebuilt other flood cars but this one is the toughest challenge so far. The Prius C has now been completely dryed out. So far I have replaced the smart key Ecu and had the replacement smart key ecu programmed with the original smart key ecu eeprom data transferred over to the replacement smart key ecu (Avi from Hybrid fix did the eeprom data swap after I sent him the old and replacement Ecus). 3 Prong Paul from Boulder Hybrids also helped a great deal with options to try to get the car in accessory mode. When I first got the water damaged Prius C with 16K miles in January 2021 i could not get the car in accessory mode. This was the the first big challenge that needed to be overcome. The body control ECU was then replaced and I got all the lights working again. The air bag ECU was replaced and the SRS is now showing no errors in techstream. The hybrid vehicle ECU was swapped out. The shift lever ECU has also been swapped out. After I replaced the hybrid battery Ecu (voltage sensor) and hybrid battery junction block assembly containing 3 relays and cleaned all bus bars and grid charged the batteries I was able to get rid of codes C1259 (hybrid vehicle control system regenerative malfunction) and C1310 (hybrid vehicle system malfunction). At the time I performed the grid charge of the battery Aug 2021 the hybrid battery was down to just over 50 volts. Many people became interested when I told them the hybrid battery quickly charged back up to full charge - approximately 160 volts since the 20 hybrid battery modules were exposed to fresh water and sat uncharged for over 9 months. I have not been able to get rid of the U code U0293 (Lost communication with hybrid vehicle control system). The car does not go in ready mode yet, the rear brake lights do not light up and the shifter does not move unless the override button is pressed. This may be because I still have the U code 0293. I need to try to pull more data with techstream that may help with assessing on how I may be able to get the car to get in ready mode.
     
  4. ChapmanF

    ChapmanF Senior Member

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    U0293 is another one of those communication codes that can be logged by different ECUs. It always means "hey I can't communicate with the HV ECU (or power management control ECU, as they started calling it in Gen 3)", but to know what that really tells you, you also should know who's saying it. A Techstream health check will show which codes are being reported by which ECUs.

    I don't have a Prius c repair manual, but in a Gen 3 liftback, the ECUs that can say U0293 include the power management control ECU itself*, the ECM, the steering, the brakes, the body (if the car has LED headlights or remote A/C), the certification ECU (smart key/wireless), the A/C, and the driving support ECU (stuff like adaptive cruise and parking assist).

    The repair manual has an extensive NETWORK -> CAN Communications System section explaining how the CAN networks are laid out, which devices are on which one, where the junction connectors are, which port is used for what, and the wire colors on each, and where the issue is likely to be based on thing A not talking to thing B.

    * Yeah, it's weird that the power management control ECU can complain about not communicating with itself, but internally (in the liftback anyway) it's divided into three different functional units. so maybe that makes it less weird.
     
  5. Prius city

    Prius city New Member

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    Chap thanks for taking time again and providing the extremely helpful information including the gen 3 ECUs that can show a U0293 (Lost communication with hybrid vehicle control system (trouble code), CAN network and repair manual information.


    You mentioned below that the main body and ECM on a Gen 3 liftback are two of the ECUs that can say U0293. Great information.


    I was curious and performed a test and confirmed that the main body as well as the ECM on a Prius C like the Gen 3 liftback can also say U0293.


    For the test on the Prius C I disconnected the hybrid vehicle electrically and tried to see if U0293 would show up in other ECUs in techstream.


    When I disconnected the top 2 of 4 connectors to the hybrid ECU I checked in techstream the main body ECU and U0293 showed up and U0101(Lost communication with TCM).


    Also of significance, with the hybrid ECU disconnected electrically I got the same codes as with the hybrid ECU connected electrically under Engine and ECT with techstream (U0293, P0102, P0113, P2118).


    I have access to Chilton DIY, Mitchell On Demand and need to decide if Toyota TIS will provide better troubleshooting procedures to help in trying to resolve the U0293 trouble code.


    I am also puzzled that when I first got the car my Innova 3160 and action scanners would read trouble codes on the vehicle and now only techstream can read trouble codes. The innova 3160 and Actron now show no communication with the vehicle. I also need to research to see if u0293 will prevent the brake light from coming on and the EV switch from lighting up and working. Any additional input from the Prius Chat community will be greatly appreciated on this challenging project - how to clear U0293 and get the car in ready mode.
     
  6. Prius city

    Prius city New Member

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    Continuing to make progress on rebuilding the water damaged Prius C. Since the stop lights (left,right and center mount) would not come on nor would the gear shifter move out of park when in accessory mode I performed further troubleshooting. I removed the 3 rear lights. I then used a small 9 v battery and confirmed that all 3 stop lights worked. I then tested out the 5 connector stoplight switch. It failed the test specified in the Chilton repair manual. I opened up the 5 connector stop light switch and saw that the internal circuit board of the stop light switch was water damaged. The stop light light switch on a 2016 Prius C has diodes and transistor(s), unlike many Toyota’s that have contact switches. I ordered a new stoplight switch from a Toyota dealer and will provide a further update once I install and provide further testing.
     
  7. Prius city

    Prius city New Member

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    Pictures of the left, right and center stop lights that were tested as well as the water damaged stop light switch.
     

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  8. ChapmanF

    ChapmanF Senior Member

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    I'm kind of hoping that you've already removed all the carpet and you've identified and checked every last electrical connection up to at least the height of that brake switch.

    If not, happy hunting and restoring ....
     
  9. Prius city

    Prius city New Member

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    Chap, I removed the carpet but checking every last electrical connection up to at least the height of the brake switch is going slow. However on a positive note brake light lights now working and gear shifter moves when car is in accessory mode. Still cannot get car to go in ready mode. Still getting


    u0100 lost communication with ecm/pcm a


    U0293 - lost communication with hybrid vehicle control system


    P2118: Throttle actuator control motor current range performance


    P0102: Mass air flow circuit low


    P0113: intake Air Temperature circuit high input


    B1441 Air Mix Damper Control Servo Motor Circuit Passenger Side


    B1442 Air Inlet Damper Control Servo Motor Circuit


    B1443 Air Outlet Damper Control Servo Motor Circuit


    B14B2 Lost Communication with Front Panel LIN.


    P0ac0 Hybrid battery pack current sensor range performance


    I am thinking as a next step I need to check to see if the ecm/pcm is bad. The ecm/pcm is sealed with adhesive and it may be hard to get open and inspect the internals. Any comments from you or anyone on Prius chat. Has anyone ever removed the cover on a late model Prius ecm/pcm that is sealed with adhesive.
     
  10. Prius city

    Prius city New Member

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    Chap, I was curious to see the condition of the inside of the ECM (located in engine bay) and if it was really water tight like Toyota claims so last night I used a a razor knife, screwdrivers and slight amount of heat from a heat gun and opened up the ECM and it was completely dry as shown in the attached. Toyota sealed that Prius C ECM very well. I will be purchasing another ECM from EBay and will then install, try to sync with the other ECUs by shorting OBD pins 4 and 13 for 30 min and then checking for changes in data with techstream to see if I can get closer to getting the car in ready mode.
     

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  11. ChapmanF

    ChapmanF Senior Member

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    I won't be surprised if the reported communication errors and HVAC servo issues turn out to be real stuff to fix in the wiring. A lot of that stuff is near or below the level of the brake switch.
     
  12. アレン・スピクタロン

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    The corrosion that is probably going to form on the fuse box and connections is going to be very difficult to remove. This repair will take long most likely, and won't be cheap, and problems could start showing up later on.
     
  13. Prius city

    Prius city New Member

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    Chap, thanks for taking time and providing the information. Still have some challenges that need to be overcome with the ac system (4 codes), connectors that need to be cleaned and 2 p codes that need to corrected.

    Avi from Hybrid fix provided a recommendation to consider to try to start the Prius C. He recommended using techstream to clear the 2 current P codes to try to trick the network of computers and then immediately try to start the car.

    The 2 current P codes are P0010 is camshaft position “A” actuator circuit (bank 1) and P0A84-123 Hybrid battery pack cooling fan 1 control circuit low.

    The recommendation that Avi from Hybrid Fix worked and the car started. Attached is a photo of the Prius C in ready mode.
     

    Attached Files:

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