Inverter pump relay, inverter or other problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by JoeG1, Feb 23, 2021.

  1. JoeG1

    JoeG1 New Member

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    Vehicle:
    2005 Prius
    Model:
    Two
    2005 Prius would not start, red triangle of death and yellow triangle followed by orange car symbol with exclamation point in center console. Car would not go into ready mode and would only shift into neutral or park. After repeated attempts it did start but stalled after about 1 minute.

    Looking for some advice on what the problem might be. Here is what I checked so.
    12V battery was a bit low maybe 11.5 volts - I recharged the battery and under load when re-inserted in the car it was reading about 12.2 volts. When I say under load the electronics booted with the above symbols being displayed and then made use of the center console and associated procedure to use the center console to read battery voltage.

    I checked the inverter coolant tank and did not see any vibration of the fluid. Again the computers were booted but the car was not in ready mode. I checked the AM2 fuse both visually and with an ohmeter and it is fine. I did not realize there are two pumps - one for the inverter and the other for coolant thermos. I checked the CHS WP relay and it appears to be defective - this relay is for the coolant thermos. I removed the relay and metered infinite resistance across pins 3 and 5. Subsequently, I applied power (12v) to pins 1 and 2 and measured the resistance across pins 3 and 5: Sometimes infinite resistance and sometimes around 20K ohms. I understand that this is the wrong relay I have been checking if I suspect the inverter, but it seems odd that I could have more than 1 electrical problem.

    I have the Haynes guide that presumably covers my model year although the wiring diagrams shown are for 2004 and 2007 - I am guessing I should be looking at the 2004 wiring diagrams? This shows a relay labeled INV WP relay which is a single pole single throw relay. It is wired in series with the Inverter water pump - at least according to the 2004 wiring diagram. I have seen others mention the IGCT relay but I think that may be for different model years.

    The problem I have is that the physical diagrams in the Haynes manual I have do not show a INV WP relay in either the engine compartment relay block 2 or engine compartment junction block/relay block (This one has all the fuses and some relays)

    My thoughts were since the fuse was OK perhaps the relay is defective, but I have no idea where it is?

    Has anyone run into this before?

    Much thanks for any replies.
     
  2. M in KC

    M in KC Active Member

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    Rather than blindly trouble shooting you really need to read the DTC that have been logged with a reader that is compatible with your prius as not all are. It will really narrow the scope for all. There are countless threads on this forum where folks had chased ghost codes from incompatible OBD II readers.

    Generally a mini VCI cable sourced from Amazon or Ebay paired with a Windows7 laptop is the most cost effective code retrieval tool. There are other compatible aftermarket readers or your local dealership can read the codes for a fee.
     
  3. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    How many miles on the vehicle, and is the HV battery the original?

    As @M in KC mentioned, use a hybrid compatible OBD2 scanner to read the codes (DTCs), this will set you in the right direction.

    Many prefer scanning with a 'mini-vci' cable (20 usd) and techstream (dealer technician software) installed on a windows device. Others get by using an OBD2 bluetooth adapter with a App like Dr Prius or Hybrid Assistant. If going the bluetooth route, be sure to read up on which adapters not to purchase : Hybrid battery diagnostic and repair tool for Toyota and Lexus

    If you feel that the inverter coolant pump isn't getting power, you can touch the pump housing using a stick/rod/pencil/finger/screwdriver, there should be a vibration. Many pumps can last between 80-100k miles, when was yours last replaced?

    Check the dealer related service history by running the VIN at : Track Your Service Records with Your Toyota Owners Account

    If you've had 12v issues, or recently disconnected the 12v battery, it would be best to also clean the throttle body and butterfly using a toothbrush wetted with rubbing alcohol or vodka, unless already clean. Spray the MAF, if you have MAF cleaner.

    Going by your description, you might have a HV ground fault, possibly in the HV battery case. After the above 'clean up', try disconnecting the 12v to reset the stored codes (DTCs), now will the vehicle start one time, and then not start the second time?

    tl;dr : Once you've retrieved the stored OBD2 codes (DTCs), please post them in this thread for additional guidance.
     
  4. davecook89t

    davecook89t Senior Member

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    I agree that your first course of action should be getting the codes read with a hybrid compatible device. I suspect you have some problem other than a non-functioning Inverter Coolant Water Pump, though. If the AM2 fuse is not blown, your car should still go to Ready mode, even with a non-functioning ICWP. To confirm that the the ICWP is not the problem, you can take it completely offline by unplugging the connector shown in Post #4 of this thread. Taking it offline is the recommended procedure when the AM2 fuse is blown and the car will not power up. It is safe to go a few miles with the ICWP not working, since it takes some time for the inverter to heat up to a harmful temperature.
     
  5. JoeG1

    JoeG1 New Member

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    Two
    Thanks for all the replies. I had the car towed to an independent shop and apparently all my symptoms were the results of a bad hybrid battery P0AA6 with subcodes 526 612. The good news was I still had full replacement warranty on the battery so I got a free replacement. Some things that I don't understand though, according to my testing the CHS WP relay was bad - but it's possible someone had posted incorrect information - not from this forum elsewhere.

    But yes working blind w/o a code reader is a waste of time.
     
  6. dolj

    dolj Senior Member

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    I presume the "new" battery with the warranty was some flavor of rebuilt/remanufactured?

    If so, expect more of the same rinse and repeat in the short term.
     
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