Mechanic say code there...My scanner say...Not there

Discussion in 'Newbie Forum' started by LEARNER, Sep 4, 2021.

  1. LEARNER

    LEARNER Junior Member

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    Not Newbie but thought this would be a good place to post.

    Run into this twice now.

    Mechanic did a scan on their professional scanning device and they come up with a code that my scanner or AC Self-Diagnostic can read if present does not see before or after or in the future.

    They say they cleared it before I can tell them (should have) not to clear any codes (I can do that).

    I do a scan afterwards and that extra code is not there and never presents in the future.

    I'm thinking a code is there or not and if your device can scan that code (Power plant code, Battery codes) and the AC Self-Diagnostic can scan AC trouble codes you should be able to see it if it exists.

    I've heard of subcodes but just speaking about the main codes.

    Please correct me if I'm wrong.

    If I'm right. I thinking keep your mechanic honest by telling them in advance not to clear any codes but then again they won't likely report that code you can't see and IF they are lieing that would be a really good test among others to screen mechanics/shops.

    Any insights? I could be completely wrong.......open to be corrected but owned a 2004 Prius since 2004 and have read a lot and have done some repairs although I know doesn't make me an expert by any means.

    One these mechanic/owner sounded pretty reputable talking with him including every review I could get my hands on.
     
    #1 LEARNER, Sep 4, 2021
    Last edited: Sep 4, 2021
  2. LEARNER

    LEARNER Junior Member

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    Correction: one mechanic did not say they cleared the code (AC trouble code)
     
  3. ChapmanF

    ChapmanF Senior Member

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    A Gen 2 Prius has about a dozen different ECUs in it that all can set diagnostic codes. Later generations have even greater numbers of different ECUs, on the order of twice that many.

    Many people have code scanners that are able to retrieve codes from at best the engine control module and maybe the brakes, because the scanners are lowest-common-denominator generic and pretty much all cars have engines and brakes. Codes in any of the other dozen or so computers in the Prius are invisible to them, and that explains the high volume of first posts on PriusChat from people saying "my car has warning lights on and there aren't any codes!"

    Some people's scan tools don't even manage to read brake codes (even though pretty much all cars have brakes). That makes it fortunate that there's an alternate light-blink method for reading brake system codes that doesn't depend on any scan tool.

    A person buying a new scan tool might want to check it, before it is really needed, to find out how many of the Prius ECUs it can actually get codes from. It can be used to pull codes from the car in the dark, or with a dark cover thrown over the solar sensor on the right side of the dash. The car will always have a B1421 code when that sensor is in the dark, so if the scan tool shows that code, at least you know it is able to talk to the A/C controller.

    Flipping the handle on the service plug on the traction battery will create a P0A0D code (in Gen 1 the code was different), so if the scan tool shows that code then, it is able to talk to the HV ECU (a/k/a power management control ECU in Gen 3).
     
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  4. sam spade 2

    sam spade 2 Senior Member

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    Do your own scan BEFORE taking it in.
    IF......your scanner is not designed specifically for a Prius, then in likely will NOT be able to properly display codes for systems that are unique to the Prius......like the traction battery and the AC system.
     
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  5. LEARNER

    LEARNER Junior Member

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    I had a Bad break accuator that was making that thumping noise driving me crazy for months. There was an extended warranty a while back for the Brake Accuator but only if the lights went off and codes set and they would replace it even though my 04 Prius was long out of regular warranty. When those light went on it was such a relief. Drove straight to Toyota to get my free accuator.

    Wonder why the long delay in the codes setting. Took there before and they knew it was the brake accuator was acting up but wouldn't change it until codes set and light went on.
     
  6. LEARNER

    LEARNER Junior Member

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    Dr. Prius will scan Engine and HV Battery codes but didn't have the engine code the mechanic reported (and cleared).

    I remember on the AC Self-Diagnostic a couple codes presenting once (I think 42 or 43) but on a recan they dissapeared. Haven't seen them since. May do physical checks for the codes using Toyota Manual.

    Maybe they are conditions that aren't quite there yet. Wondering if that's possible....
     
  7. ChapmanF

    ChapmanF Senior Member

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    That "long out of regular warranty" is part of the story. Things in cars long out of regular warranty start wearing out. The warranty extension on the actuator is to cover cases where a specific cause is why the actuator went bad, and they need the codes to confirm that. The extension is not a blanket "my sixteen year old part wore out I would like a new one please" program.

    Even the codes that they do require can be set for other reasons, but they surely figured it's better to just cover it when the codes are present than to explain to customer B why it isn't covered if customer A's was covered with the same codes.
     
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