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'04 Prius intermittent loss of traction motor. Codes point to inverter.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by stonehome, Oct 3, 2016.

  1. stonehome

    stonehome Junior Member

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    Hello, everyone. My 2004 Prius (267,00 miles, original traction battery) has been randomly losing the traction motor. If powered off and then on after 5 minutes It's driveable. I recovered these codes, and, per the service manual, checked the harness between the HV ECU and Inverter for shorts, opens and "less than 0.5volts to ground" with switch in "IG on" That last item confuses me since each end of the harness is disconnected from its electronics.Testing for induced voltage due to a bad shield, maybe?

    Anyway, here are the codes I recovered:
    CAN BUS CHECK:
    NO DTCS REPORTED
    ENGINE AND ECT
    P0171: SYSTEM TOO LEAN;
    P0420: CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)
    P0446: EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL
    P1116: COOLANT TEMPERATURE SENSOR CIRCUIT STUCK FOR COOLANT HEAT STORAGE SYSTEM
    P1121: COOLANT FLOW CONTROL VALVE POSITION SENSOR CIRCUIT STUCK
    U0293: LOST COMMUNICATION WITH HYBRID VEHICLE SYSTEM
    HYBRID CONTROL
    P0A63: MOTOR A PHASE W CURRENT (INFORMATION CODE 302)
    HV BATTERY
    U0293: LOST COMMUNICATION WITH HYBRID VEHICLE CONTROL SYSTEM (HISTORY)
    ABS/VSC/TRC
    C1241: LOW BATTERY POSITIVE VOLTAGE OR ABNORMALLY HIGH BATTERY POSITIVE VOLTAGE
    U0073: CONTROL MODULE COMMUNICATION BUS OFF
    U0123: LOST COMMUNICATION WITH YAW RATE SENSOR MODULE
    U0124: LOST COMMUNICATION WITH LATERAL ACCELERATION MODULE
    U0126: LOST COMMUNICATION WITH STEERING ANGLE SENSOR MODULE
    U0293: LOST COMMUNICATION WITH HYBRID VEHICLE CONTROL SYSTEM
    EMPS
    U0121: LOST COMMUNICATION WITH ANTI-LOCK BRAKE SYSTEM
    AIR CONDITIONER
    B1421: SOLAR SENSOR CIRCUIT (PASSENGER SIDE) (HISTORY)
    GATEWAY
    B1200: BODY ECU COMMUNICATION STOP (HISTORY)
    B1207: SMART KEY ECU COMMUNICATION STOP (HISTORY)
    B1271: COMBINATION METER ECU COMMUNICATION STOP (HISTORY)

    NOTE: wherever a code is followed by "History" it means it was previously recorded but not part of the current problem. I recorded, cleared DTCs, and then recorded a second time when the problem recurred 2 days later.

    Here's what I'm wondering: apart from the engine DTCs which I will address after this problem is resolved, is it possible that the HV ECU is failing? I ask due to the number of communication failures that show up in the recorded DTCs . Or is the inverter's current sensing of the motor's W phase failing? Or something else, like the motor itself?
    Any input, especially from those with first hand experience of this problem, will be greatly appreciated.
    Thanks.
     
    #1 stonehome, Oct 3, 2016
  2. andrewclaus

    andrewclaus Active Member

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    The P0A63 INF 302 sure sounds like sensor problem. A quote from the manual: "The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system. Thus, this does not intend detecting a malfunction in the high voltage system." Good luck fixing that--a used inverter might be the solution.

    How old is the 12V? Many codes often arise due to poor voltage.

    Sorry, no first-hand knowledge.
     
    #2 andrewclaus, Oct 3, 2016
  3. andrewclaus

    andrewclaus Active Member

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    The P0A63 INF 302 sure sounds like sensor problem. A quote from the manual: "The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system. Thus, this does not intend detecting a malfunction in the high voltage system." Good luck fixing that--a used inverter might be the solution.

    How old is the 12V? Many codes often arise due to poor voltage.

    Sorry, no first-hand knowledge.
     
    #3 andrewclaus, Oct 3, 2016
  4. andrewclaus

    andrewclaus Active Member

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    The P0A63 INF 302 sure sounds like sensor problem. A quote from the manual: "The HV control ECU monitors the inverter current sensors to detect a malfunction in the sensor system. Thus, this does not intend detecting a malfunction in the high voltage system." Good luck fixing that--a used inverter might be the solution.

    How old is the 12V? Many codes often arise due to poor voltage.

    Sorry, no first-hand knowledge.
     
    #4 andrewclaus, Oct 3, 2016
  5. stonehome

    stonehome Junior Member

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    Hi Andrew, Thanks. I changed the 12 volt aux battery about 3 years ago because things were a bit strange; engine ran the generator longer than normal after traction battery was charged, and it may have been trying to charge a very old aux battery replacement resolved the problem.
     
    #5 stonehome, Oct 3, 2016
  6. stonehome

    stonehome Junior Member

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    One additional test I neglected to mention: Removed the 3 wire plug between the inverter and traction motor and measured the following with my trusty Tektronix DMM: winding to winding resistance (50 ohm scale) 0.1 ohms. winding to ground resistance (99 Megohm scale): Open.
     
    #6 stonehome, Oct 4, 2016
  7. andrewclaus

    andrewclaus Active Member

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    Have you changed the transaxle oil? You might want to do that, and look for metal debris.

    Have you checked the 12V battery? Many threads here on threshold voltages in several conditons.

    Assuming the transaxle's okay, it sounds like you might need a salvaged inverter (only about $200 on eBay, $50 coolant), a new 12V battery (another $200+, hopefully solving the comm problems), then some engine accessory work (another $3-400) (all costs DIY).
     
    #7 andrewclaus, Oct 4, 2016
  8. exstudent

    exstudent Senior Member

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    A better question: How old AND what is the voltage under a load?

    The battery should still have some years left in it. However, it may be discharged to less than ideal voltage due to repeated short trips, a discharge event (interior light left on: trunk, cabin, map), etc. If so, this battery may be at an early death, and in need of replacement.

    The most meaningful measurement of the 12V AGM battery, is voltage under a load.
    If the car has been off for hours, or overnight, measure the voltage this way:
    1) No load (everything OFF) - measure at the battery or the jump terminal points under hood w/ a DVM.
    2) Load measurement - make car IG-ON (foot off brake, press POWER twice), turn headlights on HIGH, turn vent fan on High, turn radio on, defrost, etc. The more electrical stuff that is on (the LOAD), a better load measurement will be attained, and better idea of the battery's overall health/SOC.

    If the readings are less than ideal, try recharging the battery w/ a smart charger that has an AGM setting. Reason for using a smart charger that is AGM compatible, is the higher voltage charging threshold (13V-AGM vs 12.5-traditional). After sitting for some time, say overnight, perform a load and no load voltage measurement. If readings are still poor, time to replace the battery. At 3 years, your battery may have some warranty.

    This chart will give you a better idea of your battery's SOC and overall health. SOC is more meaningful than age. Temperature affects the reading. Colder ambient temps will produce lower voltage readings. Warmer/Hotter ambient temps will produce slightly higher voltage readings. There are charts that reflect this.
    Battery SOC Chart.jpg
     
    #8 exstudent, Oct 7, 2016
    Last edited: Oct 7, 2016
  9. stonehome

    stonehome Junior Member

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    Hi exstudent. Thanks for the SOC chart. That battery was older than I first thought, so I bought a replacement. Open circuit voltage was 12.45, but under load with switch in "IG On" it dropped down to 11.38. This with just vent fan ( highest speed), radio and HID headlights on.
    .I have a $300.00 used inverter from an '07 Prius, newer part # G9200-47120, heading my way, as I am not convinced all the codes are only from a low aux battery. I hope it's not the motor, but am changing the transaxle fluid as it's overdue. I have changed it every 70-80 K miles.
    Also have a new valve on hand to deal with the P1121 code: I can hear the existing valve cycling repeatedly (NOT a familiar noise to me from this vehicle). For $60.00 I'll swap it out......also checked the "coolant add" reservoir and the radiator: reservoir shows turbulence with car turned on, radiator was full up. Coolant was changed around 200K because inverter pump failed.
     
    #9 stonehome, Oct 7, 2016
  10. stonehome

    stonehome Junior Member

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    Update: I installed a used inverter from a 2007 salvage Prius ($300.00 + shipping). So far so good; driven about 300 miles. The coolant valve issue I reported was, well, a stuck coolant valve, which I replaced. Again, no further codes and no problems. Changed inverter coolant, engine coolant, and transaxle oil. I did use an Airlift, which made very short work of the coolant changes. Thanks to everyone who either responded to my post or had posted very useful information about the aforementioned issues.
     
    #10 stonehome, Oct 24, 2016
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