Prius C water damaged ECU rebuild

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.

 

• 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.

 

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.

 

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.

 

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

 

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.

 

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.

 

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.

 

Got the wiring issue resolved so that the Prius c goes ready right away now. Wiring problems was associated with 5 pin mini relay between certification ecu and stop light switch. 5 pin mini relay did not show on Chillton schematic I was using. From all the starts I tried battery block 9 is now 5v. All other battery blocks are 14.2-14.4v. Now getting p3000-389.(Battery Control System code). Next steps that I am thinking about - see if there is enough power in hybrid battery to spin the motor generator and perform a compression test. If not then charge hybrid battery and perform a compression test. Leak down test that I performed a few weeks ago appeared ok. Still getting clanging noise when ice starts. Ice engine keeps shutting down. Still getting p0a0f (fail to start) and p3190 (low power). Not getting any other codes like camshaft sensor, crank shaft sensor. Considering new fuel also since the Prius C has been sitting for over 10 months. If I decide to swap out the fuel I will try to use techstream to command the fuel pump and drain the fuel after removing existing fuel line at pump and adding a fuel line at pump and placing the other end in a fuel container.

 

Chap, in response to your question the attached picture I provided is the relay that did not show up in the Chilton schematic. I grid charged to Hybrid battery back up to 163 volts, drained some of the fuel and confirmed that water was in the fuel as shown in the attached. Prius C is now running well.

 

Chap, I wanted to update you on the damper/clutch on the Prius C water damaged rebuild. I am still getting a high pitch knocking noise when the ICE is running on the Prius C. A few weeks ago I test drove the Prius C and had the car up to 90 mph. I installed a timing chain kit, cleaned the EGR valve and cooler and installed new fuel injectors. Misfire codes p301 and P 303 went away after fuel injectors were replaced but the knock still exists with the ICE running. Since I did not know if the previous misfire codes damaged the clutch/damper I disconnected the exhaust, egr, right engine mount and applicable electrical connectors and then swapped 3 bell housing bolts with 3 long 10 mm x 1.25 x 110 mm. Attached is a picture of one of the 3 bolts. I used these 3 long 120 mm bolts as a guide and moved the engine up against the right side as far as I could. Jacks, blocks and boards were used underneath to hold up the engine as I moved the engine to the right. The timing cover hit the right side of the car. However, with a lot less effort than pulling the engine out of the car I was able to get a good look at all 3 springs on the clutch damper and all springs were in tact. I also removed the 6 bolts that secure the clutch to the flywheel. I got the clutch loose but did not have enough space to remove it. There were some slight cracks on the damper. I attached some pictures of the slight cracks, the gap I was able to get between engine and transmission and the timing cover up against the right side. As mentioned above I am stumped on what to try next to find what is causing noise. Seems too high pitch to me to be rod knock. Took valve cover off earlier and valve springs seemed ok. Took each cylinder to just passed tdc and checked for play through spark plug hole - seemed ok. I may need to check for slightly bent connecting rod or slightly bent valve. Any comments will be greatly appreciated.

 

Chap, last night I placed the clutch/damper onto the transmission shaft and then reached in the opening between the engine and transmission and grabbed the clutch/damper and moved it back and forth and the tapping/noise seemed like it could be similar to the high pitch knocking noise I heard with the engine running. I attached a picture of one of the 3 springs. All 3 springs are in tact but could be weak due to the misfiring that previously occurred. The 6 bolts that hold the clutch/damper to the flywheel have been removed. When I figure out the best way to get the damper/clutch out I will be able to inspect the clutch/damper more.

 

Picture of one of the three clutch/damper springs.

 

Chap, I checked out the clutch/damper in more detail. I think the clutch damper is ok and not a problem.