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Slow down light yet no Catalyst ECUs in F355 Challenge

Discussion in 'Challenge/GT Cars' started by ExcelsiorZ, May 9, 2020.

  1. ExcelsiorZ

    ExcelsiorZ Formula 3
    Silver Subscribed

    Nov 7, 2003
    1,117
    Beverly Hills
    I recently removed the plug fitted to the thermostat on a F355 Challenge and fit a proper thermostat. Odd thing now though, although the car warms up thanks to the thermostat (whereas before it would run too cool under normal driving), now the car, after being driven for 10-20 minutes and at normal oil and water temps, throws slow down lights. The first time it was for 5-8 and if pushed one bank would momentarily cut out. Babied the car home. Checked everything (and did a synthetic oil and filter change for good measure) and all seemed fine. Took the car out again and it did it again. Drove a little farther and 1-4 and 5-8 lights came on as well as red slowdown light. But here's the odd thing. I looked for the dual ECUs for the cats and of course this is a 355CH so no cats. But there are no ECUs for the cats either. Car ran perfectly fine before installing the thermostat, albeit cool. Any thoughts on what might be causing this issue after I removed the plug and installed the thermostat?
     
  2. thibaut

    thibaut Formula Junior

    Feb 28, 2004
    488
    London, UK
    Full Name:
    Thibaut A.
    Strange. I did have the odd CEL once in a while and mostly on start up: wouldn’t go away after engine starts. I unplugged both, cleaned contacts with WD40 and toothbrush and seemed happy afterwards.
    Did you try pulling the codes ? On these early models there is a way to do that with a couple of wires. It is documented in the 355 section
     
  3. ExcelsiorZ

    ExcelsiorZ Formula 3
    Silver Subscribed

    Nov 7, 2003
    1,117
    Beverly Hills
    I'll look into pulling the codes. Odd thing is I don't see any Cat ECUs and before I removed the 355CH plug and installed the thermostat I got no CEL
     
  4. thibaut

    thibaut Formula Junior

    Feb 28, 2004
    488
    London, UK
    Full Name:
    Thibaut A.
    Mine doesn’t have cats but on each side the straight tube has a lambda sond which is connected to the ecu.
    Did you try clearing memory of the ecu (battery disconnect for a fee minutes) and then doing a re-learn (idle without throttle or any electrical drain) ?
     
  5. ExcelsiorZ

    ExcelsiorZ Formula 3
    Silver Subscribed

    Nov 7, 2003
    1,117
    Beverly Hills
    Yes, but I may try this again. Does it really work?
     
  6. thibaut

    thibaut Formula Junior

    Feb 28, 2004
    488
    London, UK
    Full Name:
    Thibaut A.
    So far I managed to get rid of CEL by either cleaning up contacts of the motronic and doing the re-learn especially if for any reason I had to drive off immediately after had the battery switch off.
     
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