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Sensor shorts leading to ECM replacement?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Dave Newbold, Dec 16, 2015.

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  1. Dave Newbold

    Dave Newbold New Member

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    I am hoping the combined experience I read in this forum can help me out. I have a 2005 Prius with a history of cooling system repairs (water pump, thermostat replacements) and recently I had the dealer replace the coolant storage tank after P0116 and P0118 codes cam up indicating a defective storage tank sensor. When this happened, the dealer technician "followed the test procedure for the P0118 code and found ECM has internal failure." I declined the $ 1,150.00 repair only to discover that my passenger heat does not work (it worked fine before the coolant storage tank was replaced.)

    I live in Boston and need heat during the winter. I asked if the dealer could verify that they could find and fix any other shorts before the ECM replacement and therefore guarantee that the repair would give me a few more years of use. They could not and actually told me it could fry again immediately if there was another short.

    This seems like either this Toyota dealer is incompetent or Toyota has a poor test harness for ECM repairs. Would you recommend getting another dealer's option? Trying a salvage ECM (presumably with my local mechanic, if he dares)? or going ahead with the ECM replacement and crossing my fingers?

    I'm really not equipped to do my own repairs or diagnostics, so I'm at the mercy of the dealer. Help!
     
    #1 Dave Newbold, Dec 16, 2015
  2. Britprius

    Britprius Senior Member

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    Faulty sensors do not cause failure of the ECM. Are there still any warning lights showing faults exist? and if so what are the fault codes now showing?
    A SH ECM would be the way to go as they are not normally problematic, and readily available at cheap prices.

    John
     
    #2 Britprius, Dec 16, 2015
  3. valde3

    valde3 Senior Member

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    P0118 Is engine temp sensor high resistance. ECM has seen that engine is colder than -40c/-40F. If they did follow the diagram correctly and did get to replace the ECM problem has to be there all the time. Most of time ECM is replaced it’s not broken…
    -Basically proses is to check the engine temperature with scan tool (Mini-VCI works fine)
    -If temperature is too cold: Remove the connector from temperature sensor. Bridge the connector and check that scan tool gives engine temperature of 140c/284F
    -If it did not: Connect THW and E2 together at ECM and check that scan tool gives engine temperature of 140c/284F
    -If it did not: Confirm connections at ECM
    -If they are good: Replace the ECM
    Many times charts like that aren’t followed correctly and ECM is replaced and fault is not fixed. So I would recheck all of that.

    Has your Prius been in some accident? Rebuild? Damage to wire harness?

    If there is no heat in your car it has to be caused by some other problem than this.
     
    #3 valde3, Dec 16, 2015
  4. Dave Newbold

    Dave Newbold New Member

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    Thanks John. I do have a Check Engine light on, so I assume there are codes available. Therefore, I assume you think I should verify those first, even though the heat doesn't work and the dealer already mentioned the faulty ECM (and told me the heat issue is from the faulty ECM.)

    What is a SH ECM? A third party version or a salvaged version? Is this something my usual mechanic could install for me (the dealer says that ECMs are bound to specific vehicles and "normal" mechanics can't do this. Correct?

    Thanks in advance for any further details!
     
    #4 Dave Newbold, Dec 16, 2015
  5. valde3

    valde3 Senior Member

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    SH is short for second hand.
    What do you mean by no heat? No heat even in max hot? If you’re really not getting any heat there has to be some other problem.
     
    #5 valde3, Dec 16, 2015
  6. Dave Newbold

    Dave Newbold New Member

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    Valde3,
    I am thinking that your diagnosis is probably better than my dealer's. I'm not a DIY type and don't have the tools, so I guess I should either try another dealer or see if my local repair guy can follow your advise. Right?

    Correct, no heat even in max hot.
     
    #6 Dave Newbold, Dec 16, 2015
    Last edited by a moderator: Dec 16, 2015
  7. valde3

    valde3 Senior Member

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    Anyway start by checking or having somebody else check (with correct diagnostic tool (Mini-VCI is good and cheap)) all fault codes.
     
    #7 valde3, Dec 16, 2015
  8. Britprius

    Britprius Senior Member

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    It is quiet possible the dealer has not removed all the air from the system after the work on the cooling system. This could be the reason why you have no heat, and a fault code.
    Bleeding all the air from the cooling systems in a Prius is a little problematic "needs patience", and can lead to a number of problems indicative of those you are experiencing.

    John
     
    #8 Britprius, Dec 16, 2015
    valde3 likes this.
  9. Dave Newbold

    Dave Newbold New Member

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    Thanks John and Valde3. Will get the new codes and ensure air is bled from the system and report back on this thread.
     
    #9 Dave Newbold, Dec 16, 2015
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