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Prius v won't start up after changing head gasket

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by hxs90, May 17, 2024.

  1. hxs90

    hxs90 Junior Member

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    Hey guys,
    I replaced my head gasket and did the EGR component cleanings last night but not my prius will not startup at all. When I go to start it up it all the lights on the dash are lit up. I can hear the inverter kick in but the cars engine doesn't kick on. I pulled the codes and got P0121, P0123, P0222, and P2135 indicating issues with the Throttle/Pedal Position Sensor/Switch.

    What I thought happened was that I somehow damaged the throttle body sensor while cleaning it. I checked the connectors on the throttle body with a multimeter and they were reading low so I went got a replacement throttle body from a junkyard. The replacement throttle body connector reading was within the 0.3 to 100 ohm range, indicating it was in working order. However, the issue still persists and I am at a loss on what to do. I went through all the electrical connections to make sure they were all plugged in properly as well.

    Has anyone come across this issue after doing the head gasket or cleaning the EGR components and can guide me on how to overcome this issue?
     
  2. ChapmanF

    ChapmanF Senior Member

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    Yeah, that SAE-standard fortune cookie tries to cover so many different cars it's like a riddle. So is it the throttle or the pedal position? And is it a position sensor or a switch?

    As it happens, the Prius doesn't have any throttle or pedal position switches, and the throttle and the pedal both do have position sensors, and the codes for both all share the "Throttle / Pedal Position Sensor" fortune cookies, except if you look at the full fortune cookie, the codes for the throttle say "A" Circuit and/or "B" Circuit, and the ones for the pedal will say "D" Circuit and/or "E" Circuit. More details are here.

    The codes you have all pertain to "A" and/or "B" circuit, so looking at the throttle body was the right move.

    What measurements did you make with the multimeter, and what were they, and what was your source of information for what would constitute "reading low"?

    Same question about what you measured, and in what source did you see a "0.3 to 100 ohm range" that would indicate it "was in working order"?

    The Toyota Repair Manual offers such a range for checking the throttle motor (pins 1 and 2 of the connector), which you would be directed to check if you had codes P2102, P2103, or P2119 pertaining to the throttle motor. But you haven't got any codes about that motor; the codes you have are about the position sensor.

    The position sensor contains Hall effect electronics so you don't really learn much by sticking an ohmmeter on it. You'll see the troubleshooting steps for the codes you have involve simple continuity testing of the wiring, and a supply voltage check.

    Does "the issue still persists" mean you have the same trouble codes with the replacement throttle body that you had with the old one? That suggests that some close attention to the wiring you disturbed might pay off.

    What are you using to read trouble codes? When you say "all the lights on the dash", that sounds like more than the check-engine light, but the only codes you have listed here are codes from the ECM. That makes me wonder whether there are more trouble codes than your scan tool is showing you. Is the triangle light on?

    What sound do you hear, and when, that you describe this way?
     
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  3. hxs90

    hxs90 Junior Member

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    I measured ohms on both the old and new throttle body connector. The original was giving me a reading of under 0.3 ohms. I referenced this from the Repair manual under the "throttle body inspection" section. If I read it correctly I think it was just to check if the throttle body assembly connector had the correct resistance, and if it was within the 0.3-100 ohms range that it was good? Since it wasn't 0.3 ohms or above to replace the whole throttle body assembly. I also checked the voltage for the connector (3rd and 5th pin) going into the throttle body and I got 4.75 volts which according to the service manual is within range (4.5 to 5.5 V).

    Yes, the codes still pop up when I scan it with Torque app. I checked and rechecked all connectors and don't see anything out of place.


    I have an OBD scanner and the Torque app to read the codes. I've rescanned about maybe 10+ times and it's the same codes that pop up. Nope, the triangle light did not come on. I'll attach a picture of what the display looks like when I attempt to power the car on. IMG20240517172818.jpg


    Sorry, I don't think that's correct. But it's the "errrr" typical sound you hear when you power it.

    I forgot to mention that we checked the wiring harness connecter (the one I mentioned above that I tested voltage on) to the throttle body with the ECM for an open, which all measured out to be 0.1 ohms. When checking for shorts we were unable to detect any measurement. Correct me if i'm wrong, but according to the picture below, it states to check the wiring harness connector to the throttle body OR ECM to a ground? Because that's what we were trying to do and we had no luck getting a reading on anyone of them they tell you to check.


    upload_2024-5-17_22-55-0.png
     
  4. ChapmanF

    ChapmanF Senior Member

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    I possibly shouldn't have said "triangle light". I meant the Master Warning Light, which was a triangle in gen 1, gen 2, and the gen 3 liftback, but I think in the v they made it the car-exclamation-point that I think I am seeing over in the right corner.

    So for short checking, your meter display just never changed from the overrange-ohms reading it was showing while you didn't have the probes on anything? That's actually ok; where the manual says > 10 kΩ, they really mean there should be at least that much resistance to ground. If it's so much resistance that your meter reads overrange, so much the better.

    But that good news is also sort of bad news, because it means you don't seem to have found a simple wiring problem.

    If I were in your situation, I would probably want to look in the code freeze-frames for the values of VTA1 and VTA2. I don't know if Torque can show freeze-frames. It might show live data and you could watch live VTA1 and VTA2 readings while moving the throttle. The two readings are not supposed to be identical, but to track each other in a mathematical relationship (as described in the manual); the ECM uses that redundancy to decide if it trusts the sensor.

    The trouble code detection conditions describe just what needs to seem wacky about VTA1 and/or VTA2 to trigger each code. Maybe seeing the actual readings would give a hint at what's going on.
     
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  5. hxs90

    hxs90 Junior Member

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    So I tried turning it on just now and the car simply won't even power on. When I try to power it on, I can hear a weird whining noise coming from the inverter in the engine bay. At this point I might just have it towed to Toyota and have them take a look at it and see what they say.
    Video of noise: VID20240518100952.mp4.
     
  6. ChapmanF

    ChapmanF Senior Member

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    Can't say I've ever heard that sound before, but the inverter wouldn't be my first, second, or third guess for the source of it. A mechanics' stethoscope (or even a stick) might be in order.
     
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  7. rjparker

    rjparker Tu Humilde Sirviente

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    Let’s backup a bit. Did you pull the orange hv battery disconnect in this process? If so a common issue is an incomplete two step insertion.

    The whirring sound is not the inverter. Typically it is the normal brake booster pressurization.

    By now your 12v may be low. What is the current voltage?
     
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  8. hxs90

    hxs90 Junior Member

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    Nope, didn't touch the hv battery or disconnect it.
    The battery was my first thought too. I checked the rear/trunk battery and its showing me a reading of 11.93 v currently.
    Interesting, what exactly would be the cause of that noise from brake booster pressurization?
    IMG20240518131009.jpg
     
  9. hxs90

    hxs90 Junior Member

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    oh lol. I just thought it was the inverter because I was hearing it there. I unfortunately don't have a mechanics stethoscope on hand.
     
  10. rjparker

    rjparker Tu Humilde Sirviente

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    Brake booster noise is normal although sometimes it gets more frequent as it gets older.
     
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  11. hxs90

    hxs90 Junior Member

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    Out of curiosity, do you guys know off hand if the harness connector going into the EFI vacuum sensor is supposed to have 3 pins or 4? I feel like there is a pin missing. The sensor itself looks like it has all 4 pins. IMG20240517170145.jpg IMG20240518132945.jpg
     
  12. hxs90

    hxs90 Junior Member

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    ahh ok, thanks for letting me know.
     
  13. rjparker

    rjparker Tu Humilde Sirviente

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  14. ChapmanF

    ChapmanF Senior Member

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    I'm not at all convinced that's what that sound is. I've heard the brake pump hundreds of times, in multiple Prii. The sound in your recording, I haven't.

    Mechanics' stethoscopes are really cheap, a handful of dollars for a real one, plus you can often learn plenty with nothing more than a long screwdriver or a stick.
     
  15. hxs90

    hxs90 Junior Member

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    I'll look further into it. Do you just kinda feel for vibration if using a ling screwdriver or stick?
     
  16. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    That works. You can also set the near end against your jawbone in just the right spot, and you'll hear it clear as day through bone conduction.
     
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  17. rjparker

    rjparker Tu Humilde Sirviente

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    This is the one I was calling Brake Booster. Before it went totally dead.

    No Ready since hg?

    It has never spun the engine since the hg?

    You never even touched the orange hybrid battery disconnect?

    Have you checked your fuses? It would be quite easy to blow one while troubleshooting.

    Normally these problems after hg repair turn out to be ecu connectors not fully engaged or fuses. If it spins and does not start that is another issue.

    Now you get nothing? If it were me I would trace the 12v at several points including those feeding the ecm since you were testing there:

    Incoming 12v
    Fusible links 1.jpeg

    ECM and Fuses p1-3
     

    Attached Files:

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  18. hxs90

    hxs90 Junior Member

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  19. rjparker

    rjparker Tu Humilde Sirviente

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    Your 12v battery is definitely bad if it goes to 7 v under load. That detail should have been mentioned earlier.

    It will sometimes float up without load but it probably has the capacity of a pair of AA batteries.

    The smart thing to do is replace that battery. If you jump it DON’T screw up with a reversed polarity and blow more stuff! Feeding that drained battery with a jump box or even another car may not immediately raise the dead battery voltage quickly. Toyota says hook up and wait 5 minutes with the jump energized in an attempt to fast recharge the dead one.
     
  20. hxs90

    hxs90 Junior Member

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    Yeah that's what I figured too. My bad, it's just been a frustrating couple of days.

    I'm looking at just replacing it today once my sister-in-law comes back.

    I really appreciate your input into this. I see that you contribute a lot to this community and a lot of the people speak highly of you.