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P0A4C & P0A4D - ICE shut down at about 70 mph

Discussion in 'Gen 2 Prius Technical Discussion' started by Mattp, Apr 11, 2021.

  1. Mattp

    Mattp New Member

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    Location:
    Fort Worth, TX
    Vehicle:
    2009 Prius
    Model:
    N/A
    The issue...
    Red Triangle and all the warning lights

    The car
    2009 Prius - 230,000 miles

    When I hit about 70mph on the highway the ICE completely shuts off leaving me to coast off the hybrid battery. If I pull over and turn the car off wait about 30 seconds the car comes on and will operate on the ICE for a short burst then back to battery. I can use this to get off the highway.

    Once off the highway and taking normal residential like streets (anything below 60mph) the car will operate like normal. The ICE and hybrid system will operate in tandem just like you would expect. During this time the warning lights stay active.

    First time it happened after the car sat over night it was fine the next morning with zero warning lights. On the way to work after about 20 miles it triggered off and I had been going 70+mph for about 10 miles. Let it sit all day and work and the lights are off again. Then on the drive home after only a little bit of driving at 70+ it lit everything up and shut off the ICE (I should state that every time the warnings pop that the ICE shuts off). Limped home via backroads under 70 and never had an issue but the warnings were still on.

    I've heard the hybrid battery fan kick on the first 2 times this happened, but not this last time. This is because I did see my inverter pump had hardly any flow in the tank. Swapped it out and had a dude. Swapped in another and now that tank has tons of movement. I've pulled the codes P0A4C & P0A4D.

    Looked at the wires behind the glove box and they look fine. Can't see any issues with the little connectors on the side of the transaxle. But the issue still surfaced again today after I went ahead and swapped the battery with a new one. The old one had a production date from 2012.

    Todays event I was watching the info screen. Battery had 2 bars as I entered the highway. Hit 70mph and off went the ICE, just at the end of the on ramp. Immediately plugged in the scanner and found only my trusty old P0A4C & D codes. Limped off the highway via stopping, turning off entire car, waiting 30 seconds, turning back on so that the ICE was alive, driving about .5 miles before ICE shuts down, and repeat. Once on the access road and road home (about another 7 or 8 miles) the car ran fine never once killing the ICE. But again Triangle and check engine stayed on the entire time. Oh and the hybrid fan never kicked on during this issue today.

    So my issue is that the ICE will shut off at highway speeds but seems perfectly fine cruising around doing little around town tasks. I've done the inverter pump, I've visually inspected the wires, and I've cussed the gods. My fear is that it is the hybrid generator, but nothing I can pull up says "oh yeah btw the ICE will shut down with this issue". Would love to have help with this please.
     
  2. SFO

    SFO Senior Member

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  3. T1 Terry

    T1 Terry Active Member

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    Vehicle:
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    My guess is either a blocked fuel tank breather or a blocked fuel filter. My Australian built 2008 Gen 2 suffered from a blocked catalytic converter and it turned out a blocked fuel filter was causing it to run lean and this lean run cleaned the carbon build up out of the exhaust before the Cat and blocked it. Fortunately here in Australia, you can buy an after market Cat for $120 and the fuel filter is under the body between the fuel tank and the ICE so easy to swap out for a new unit. Now the 2008 Prius goes like a rocket again, even though it has 730,000km on the clock.

    Worth doing a fuel flow test, unfortunately I know nothing about how the US model Prius powers their fuel pump so I can tell you how to just power up the pump so you can measure the fuel delivery over 1 min, how many ltrs, well USgal i guess for a US production model.

    T1 Terry
     
  4. TMR-JWAP

    TMR-JWAP Senior Member

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    Battery had 2 bars as I entered the highway.

    This is a bit unusual. Perhaps you're having some engine power issues? While you're rolling along at speed, is the battery recharging or is it depleting further?
     
  5. ChapmanF

    ChapmanF Senior Member

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    I would definitely go through the workup for the codes you have, as posted by SFO.

    The generator resolver is a critical component that tells the HV ECU the rotating position of the MG1 rotor to 1/4096th of a revolution at all times, which information the ECU needs so it can properly shape the electric waveforms to/from MG1's coils. If it can't trust that signal it can't control MG1. If it can't control MG1 it has no way to make use of power from the engine. I don't think it would be time well spent here to be looking in other directions than where the codes point.

    The resolver itself is the only part of the resolver circuit that's inside the transaxle, but it is such a simple device there's hardly any way for it to be bad. The issue is probably something else fairly simple and repairable,
     
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  6. Mattp

    Mattp New Member

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    Location:
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    Vehicle:
    2009 Prius
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    N/A
    The scanner I used was a - INNOVA 5310

    I've kind of looked at the wiring in those instructions. The wires on the HV ECU behind the glove box all looked good. Pulled the top plugs and inspected it for any defect, looked perfect. As for the 3 plugs on the transaxle, I've only visually check the top to by the water pump, which looked ok on the wires. I'll get the jack out and look at the one above the drain plug this weekend.

    As for what the battery is doing once the engine shuts off. While trying to stay with traffic to get to a safe spot to pull over the battery drains down. But if I get a chance to coast or brake the battery does show that it is getting a receiving charge, via the HUD.

    While on roads below 50mph the car operate exactly as it should.

    But my real question as someone who has always worked on my own cars since I was 15 is this... WHY would the hybrid system shut down the ICE, if the problem (based on the codes pulled) is based in the hybrid/electric system? This feels kind of counter intuitive as the codes say issue with hybrid parts, but the computer says ok kill the ICE and lets keep operating the part we have an issue with.

    Thanks for the additional ideas. The fuel filter would make sense as a lean out issue at higher speeds thus killing the ICE.
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    The synergy drive system MUST have proper function of MG1 in order to do anything with the ICE. So if there is any glitch with the MG1 resolver, it can't use it to charge or transfer torque to the wheels etc- so shut down is the safest option. You might be able to keep MG2 going a bit until the HV pack is run down (as a "get out of the middle of the intersection" option).

    I suspect you have an intermittant open circuit in the wiring at or near the transmission connector. For your problem I suggest unplugging the hybrid ecu connector (for the harness to the transmission), then back probe two of the wires for one of the resolver coils and measure resistance- watch (or listen if your meter has an audible continuity function) while gently wiggling the harness at the trans and its connectors. Repeat for the other two coils.

    Posted via the PriusChat mobile app.
     
  8. Figster10

    Figster10 Member

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    Hey I'm currently having the same issues with my car. 2005 prius 200k or more since not true mileage. I work on a lot of hybrid batteries as a side gig and have installed 3(three) batteries reconditioned. I am going to see about messing with the 12v and getting another hyrbid battery from another car to rule that out. If I coast 45 mph I notice know problems as well. When I drive 20 miles on the freeway it runs almost like quietly going limp and the charge drops to 2 bars struggling to get back up. I work on these gen 2 a lot but this one is weird. I have techstream just need to see what exactly to do first.

    Issues: drives fine on roads, struggles after 10 miles on freeway. Abs, vsc, Triangle turns on and I ride through it until eventually car dies out and after I let it sit and delete codes it turns on and I have to coast it back like nothing happened.

    Codes that pop up are u0100, u0111 lost control with ecm/pcm, lost communication with battery energy

    Live diagnostic readings show all leveled cell readings on hybrid battery.

    talk to me, folks.

    I'm hearing clogged fuel filter, possible 12v battery connection/voltage
     
  9. mr_guy_mann

    mr_guy_mann Senior Member

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    Connect your techstream and pull up data for the engine ECM or the battery ecu then drive it to confirm what loses communication when the fault occurs. From the codes given, you have something messing up the CAN network data bus between those modules. If the engine, hybrid control and HV battery ecu's can't talk, then the car can't run at all.

    That could be an intermittant CAN wiring fault (short or open circuit, possibly a loose connection) or a module on that network could be briefly losing power or ground. You need to get wiring diagrams for your car and get REALLY good at reading and understanding them. Network comm faults can be among the most challenging problems to fix.

    A bad 12V battery or connection can cause all sorts of grief on a Prius, but I would not expect that to affect it only at higher speeds. Usually it would glitch right when you started the car.
    Posted via the PriusChat mobile app.
     
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  10. ChapmanF

    ChapmanF Senior Member

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    If you're really having "the same issues", namely the P0A4C and P0A4D in the title of this thread, then it would make sense to focus on the workup steps for those issues, which were posted upthread.

    If not, starting a different thread for the issues you are having would help avoid mixing up suggestions.
     
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  11. Figster10

    Figster10 Member

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    I was asking what exactly happened in your experience perhaps it could be my exact issue. Nothing more and nothing less.
     
  12. ChapmanF

    ChapmanF Senior Member

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    What codes do you have? If they're not P0A4C and P0A4D, that rules out being the same issue.
     
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