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Check engine light when it's warm

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by FirstFlight, May 13, 2012.

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  1. FirstFlight

    FirstFlight Member

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    I don't have a scangauge and can't afford one right now so I thought maybe posting here would help.

    Last year my check engine light came on a couple of times at the end of the summer but it went away and I can't remember how. Today was the warmest day of the year so far for us and my check engine light came on again. It seems to happens when it's warm, I'm accelerating and I think the A/C is on but I can't be 100% sure about that.

    I popped open the hood and looked around but I didn't see any issues. All of my fluids were at the correct level and my engine wasn't hotter than it should be. I believe there is a 2 MPG drop but I've only been through 1/2 of the tank so I'm not sure about that.

    Without having a scangauge, are there any other cheap alternatives to finding out what code is logged? I've heard that Toyota charges something like $80 to find out.

    Any other ideas that could help me?
  2. KL0RN

    KL0RN New Member

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    you might look online for the cheap ($20) Bluetooth OBD2 reader. yes, they have a 50/50 chance of working, but so far for my PC and Android, it works great for pulling codes.
    Cheap yes, but may be enough to get you by..
  3. richard schumacher

    richard schumacher shortbus driver

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    Sounds like a bad inverter coolant pump. If you burn up the inverter replacing it'll cost about $2K, so whatever you're gonna do, do it soon.
  4. FirstFlight

    FirstFlight Member

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    Strange. It was just replaced in December of 2010 for a recall.

    The check engine light has gone out and it hasn't come back. However, if I get a scangauge, will it show the code that lit the check engine light and if so, would that code point to the inverter coolant pump if it was the issue?
  5. HaroldW

    HaroldW Active Member

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    It is possible you have air trapped from when they changed the inverter pump. I would take it in and tell them to bleed the system properly this time. They obviously did a poor job of it when they changed the pump?. H
  6. FirstFlight

    FirstFlight Member

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    I doubt this is the cause. They replaced it at 117K miles and my car now has 168K miles. It wasn't a problem during 80% of the hottest part of the summer last year.
  7. GrumpyCabbie

    GrumpyCabbie Senior Member

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    If your a/c gassed up correctly? Do you have dogs? Do you carry anything on the back seat or was anyone sitting there when the light came on?
  8. FirstFlight

    FirstFlight Member

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    I did think about the back seat by the vent. When the light came on, nobody was in the back blocking the vent and I don't have any animals. How can I check the fan though? Does it run 100% of the time? Can I put a piece of paper over the vent and see if the paper gets sucked in towards the vent?

    Regarding the A/C, I have no idea. The A/C works pretty good though. If I can figure out in what situations the light comes on, I can turn the A/C off and see if it's the cause.

    I'm going to try and borrow someone's scangauge or OBD2 reader to see if the code is logged.
  9. FirstFlight

    FirstFlight Member

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    I got a hold of a scangauge today. My code is a P0420. Catalytic converter? How bad am I screwed?
  10. seilerts

    seilerts Battery Curmudgeon

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    It's not bad at all since you are not in CA. Eastern makes a direct fit, #40712, for about $300. Remove the downstream O2 sensor, four bolts, and slip the old one off the hanger. Installation is the reverse.
    1 person likes this.
  11. FirstFlight

    FirstFlight Member

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    Could the sensor be the problem? If so, are one of these the scangauge inputs:



  12. seilerts

    seilerts Battery Curmudgeon

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    You need a graphing scantool to differentiate a P0420 caused by a bad O2. Even then, it is very difficult to interpret the results. If you roll into a shop with a P0420, they will have you replace the cat and both O2s, because they don't want to waste time trying to confirm the diagnosis.

    If you could spot a bad O2 on a ScanGauge, the computer would set a different code.
  13. FirstFlight

    FirstFlight Member

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    Gotcha. The other thing is, the freeze data stated:

    RPM - 2742
    TPS - 34
    Loop - Open
    WT - 190
    LOD - 57
    IGN - 16
    IAT H - 101

    Shouldn't the loop be closed?

    Also, I got the red triangle and some other yellow light today. The yellow light has two arrows pointing up and down on the left and almost like a "D" inside the yellow portion. The codes that came up when the yellow light and red triangle were on are:

    P0003
    P0004
    C2D86
    B0667
    C2086
    B0665

    The car runs fine as far as I can see. My SOC was 66, battery temp was 102, engine water temp was 170, RPM was 1800 and I was gently driving at 42 MPH. I've looked up these codes and some I couldn't find but the P0003 and P0004 are a conflict - One is fuel volume high and one is fuel volume low.

    I've read that the scangauge can set off certain codes but I cleared them and disconnected the scangauge and they red triangle still appears. When I try to see what codes are there with the red triangle, the scangauge says that no codes are present.

    Too many issues here and I'm not sure where to start.
  14. uart

    uart Senior Member

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    Sorry I cant help with the codes. With the closed loop however I've heard that you may have to be in hybrid stage 4 (after the 5 to 10 second idle when the engine cuts out) before it enters full closed loop operation. Could you please try confirming this (let the prius get fully up to temperature then let it idle for 5 to 10 seconds until the engine cuts off). Then see if it goes into closed loop operation.
  15. FirstFlight

    FirstFlight Member

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    I can tell you that the car had been running for 30+ minutes and I was climbing a hill. Regarding this incident, the light went away the next day and didn't come back until today. I'm really confused. The problem is erratic but today is the first time the light came on again and it came on during light driving.
  16. uart

    uart Senior Member

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    It doesn't matter how long you've been running or how warm the engine is. It wont transition to "stage 4" until you stop and let it idle for 5 to 10 seconds, until the engine cuts out. If you stop and the engine is already off then you have to tap the acclerator until it does come on, then idle for 5 to 10 seconds and then cut out. Bizarre I know, but true.
  17. FirstFlight

    FirstFlight Member

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    I see what you're saying now. I can't remember if I stopped or not and I'm not sure if it was in S4 or not.

    If I understand your question correctly, once I start moving, never stop. Then monitor the loop to see if it's closed or open throughout the entire trip. Is this correct?
  18. uart

    uart Senior Member

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    Yeah, kind of simpler. Just warm it up and then stop and let it idle to enter S4. Then once in S4 go for a drive and see if it reports being in closed loop.
  19. FirstFlight

    FirstFlight Member

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    Do you just confirm S4 by water temp?
  20. uart

    uart Senior Member

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    I don't even have a scan gauge. I just tell if it's in S4 by how it behaves, cutting off the ICE as soon as you back off the gas pedal (even under 35 MPH). It wont do that in S3.
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