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Cat ECU'S 355

Discussion in '348/355' started by Vegas-Guy, Feb 2, 2008.

  1. Vegas-Guy

    Vegas-Guy Formula 3

    Nov 25, 2007
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    Hey guys,

    My 1/4 light came on again today, stayed on most of the day...:( I've already put in a new Cat, and replaced both O2 sensors. Now I want to switch the EC's to see if my 5/8 will come on instead of the 1/4. My question is do I need to do anything special for this, or can I just switch them and start it up.:confused: Thanks again for the help.
     
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  3. 3forty8

    3forty8 F1 Rookie
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    95? Motronic 2.7? I'm pretty sure you can pull the error codes on that ECU using the procedure that the 348 2.7 Motronics uses (No Doubt's page/Ernie's instructions). Might be more useful than swapping ECU's; if you switch them it would be a good idea to disconnect the battery and let it idle for 10-15 minutes to re-learn on start-up.
     
  4. Vegas-Guy

    Vegas-Guy Formula 3

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    yep it's a 2.7
     
  5. Ricambi America

    Ricambi America F1 World Champ
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    Just change them from side to side.

    Honestly, you can probably tell if it's broken just by taking a good hard look at the backing seal. If it's black, it's crap. If it has cracked away from the housing, it's almost certainly cooked.
     
  6. UConn Husky

    UConn Husky F1 Rookie

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    Mine is black and cracked...isn't that ok as long as water hasn't gotten into it yet? I'm hoping to just seal it up with silicone.
     
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  8. Ricambi America

    Ricambi America F1 World Champ
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    Yes, it's probably ok. Use something that can withstand the heat... and just realize, it is probably going to fail eventually. Odds are, it'll be when the *next* owner has the car, so who cares, eh? (I'm just kidding of course. My car doesn't even have those damn things)
     
  9. Vegas-Guy

    Vegas-Guy Formula 3

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    #7 Vegas-Guy, Feb 3, 2008
    Last edited by a moderator: Sep 7, 2017
    I just want to make sure were talking about the same ECU's. It's #69 on this picture?

    I should be able to just switch them from side to side to see if the 5/8 light comes on instead of the 1/4?
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  10. Ricambi America

    Ricambi America F1 World Champ
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    Correct.
     
  11. Oengus

    Oengus F1 Veteran
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    Why dont you just get some test pipes from Daniel and be done with the ECU's?
     
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  13. Vegas-Guy

    Vegas-Guy Formula 3

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    I've been thinking about the hyper-flows...:D
     
  14. Oengus

    Oengus F1 Veteran
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  15. Vegas-Guy

    Vegas-Guy Formula 3

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    #12 Vegas-Guy, Feb 3, 2008
    Last edited by a moderator: Sep 7, 2017
    Ok so I took off the covers to change the ECU's for the cat's and found this. Could this be the reason for the 1/4 light to come on?

    The first picture is the drivers side..:) the second the passenger side..:eek:

    I also switched the ECU's just in case, what a pain in the a@@. It was easy just a pain..

    P.S. Both of the ECU's looked ok for the most part. But they both had a very slight crack starting at the base of one of the inserts.
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  16. No Doubt

    No Doubt Six Time F1 World Champ
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    Not getting much ram air that way, eh?!
     
  17. Oengus

    Oengus F1 Veteran
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    Yikes,

    Id put the mesh tube back and give it a try....
     
  18. Vegas-Guy

    Vegas-Guy Formula 3

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    I wish I could it's raining today...:( I hope I can take it out tommorrow
     
  19. Vegas-Guy

    Vegas-Guy Formula 3

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    I was able to take the car out today to see if the 1/4 light would come on again. I'm still not sure if the air intake in the picture above would make the light come on or not, never really got a answer from anyone.

    I put 50 miles on it and NO light...:) I would have drove more but it's really windy (40mph) and didn't want to chance it. Just as I was pulling in the garage the light came on...:( but this time it was the 5/8. Since I was in the garage I grabbed the lazer temp gun and put it on the cats just to make sure they weren't to hot. Both were about 390-400 on the intake side...:)

    Guess that means I need a new ECU...:(
     
  20. No Doubt

    No Doubt Six Time F1 World Champ
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    The Motronic 2.7 355's should have 4 dash lights that matter, yes?!
    SlowDown 1-4
    SlowDown 5-8
    Check Engine 1-4
    Check Engine 5-8

    You are seeing which?
     
  21. Vegas-Guy

    Vegas-Guy Formula 3

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    slow 1-4
    and today after switching the ECU's slow 5-8
     
  22. No Doubt

    No Doubt Six Time F1 World Champ
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    OK!

    Time for a new cat ecu, then.
     
  23. Oengus

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    Sounds like a new ECU is in order
    or some test pipes :)
     
  24. ernie

    ernie Two Time F1 World Champ
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    Okay

    1) Check the resistance on your Mass Air Flow sensors. Make sure that they are at 383 ohms.

    2) Don't be so quick to change the cat ecu's just yet. The thermocouples have been known to go bad. So you may want to try swapping those from side to side and see what happens.

    3) You want to check the cat temp on the exit side of the cat. Because that is the side that the thermocouple is on, and where the exhaust will be hotter if indeed your cat/s are running hot. If you get are getting 390-400deg F reading with the infrared temp gun then it has to be a bad thermocouple, or cat ecu, or both. The slow down lights will flash if the cat temp gets to 1652 deg F (+/- 30*F), and if the cats get up to 1724 deg F (+/- 36*F) the light stays on steady. So if you are get a slow down light, and then you take a temp reading immediately off of the exit of the Cat of 400 deg F, then you know the cat ecu is getting/giving a false reading to the Motronic.
     
  25. jetfixr

    jetfixr Formula 3

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    +1 on test pipes. Get rid of that junk....
     

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