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355 slow down light

Discussion in '348/355' started by tim355, Apr 25, 2015.

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  1. tim355

    tim355 Karting

    Nov 7, 2003
    57
    #1 tim355, Apr 25, 2015
    OK so i've read all the threads on the slow down light issue i can find but nothing has helped me solve my problem. I have a 1995 2.7 motronic system. My 1-4 bank slow down light comes on right when i turn the key on AND STAYS ON AFTER I TURN THE CAR OFF for a few seconds. After i turn the car off I hear what sounds like a relay clicking in the passenger footwell fuse box area and then the light goes off.

    I've swapped ECU's......no help
    I've swapped thermocouples.......no help
    I've disconnected the thermocouples from the ecus and drove the car around.......no help
    I've reset the computers by turning off the battery and running 20 min......no help

    Any ideas?.....anyone?
     
  2. tim355

    tim355 Karting

    Nov 7, 2003
    57
    #2 tim355, Apr 25, 2015
    Oh..... and one other thing. The car runs great. The computer is not dropping the bank
     
  3. WATSON

    WATSON Two Time F1 World Champ
    Owner Rossa Subscribed

    Sep 9, 2010
    23,683
    WI
    #3 WATSON, Apr 25, 2015
    Does the 2.7 have a thermocouple on the bypass valve?

    On my 5.2 I had the same problem. Turned out the pro that did my engine out managed to swap the leads on the CAT ECU's between the bypass and the RH bank thermocouple. I put them back as spec'd and all was good.
     
  4. emac

    emac Formula Junior
    Silver Subscribed

    Sep 14, 2014
    851
    upstate SC
    Full Name:
    ernest
    #4 emac, Apr 25, 2015
    We must have had the same pro! I had the same issue.
     
  5. drbob101

    drbob101 F1 Rookie
    Owner Silver Subscribed

    Nov 26, 2012
    3,821
    Tinton Falls, NJ
    Full Name:
    Bob Ferraris
    #5 drbob101, Apr 26, 2015
    95s don't have the bypass TC

    The clicking in the footwell is unrelated to the SDL IMO.

    Does the SDL switch sides when you switch complements? Does it ever blink or just go solid right away?

    Tap the outputs of the cat ecu s
    and see what voltages they are sending.

    If the SDL stays on the right side even when you switch parts around then

    1) you have multiple blown parts. Unlikely because the bad part would switch the sdl to the other side

    2) there is a bias voltage in the cat ecu output line that will show 5v if anything is unplugged. If there is a wiring or connector issue on that right side this could be the issue

    I woukd start with tapping the outputs so you can see the results of your diagnostic switching of parts first.
     
  6. tim355

    tim355 Karting

    Nov 7, 2003
    57
    #6 tim355, Apr 26, 2015
    The SDL stays solid right away never blinks. The SDL stays on the right side even when I switch components.

    I will check output voltage on the ECU's and report back.

    Thanks for the feedback, everyone.
     
  7. emac

    emac Formula Junior
    Silver Subscribed

    Sep 14, 2014
    851
    upstate SC
    Full Name:
    ernest
    #7 emac, Apr 26, 2015
    Dr bob helped me out a lot with my sdl light. Follow his advice and it will all start to make sense.
     
  8. emac

    emac Formula Junior
    Silver Subscribed

    Sep 14, 2014
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    ernest
    #8 emac, Apr 26, 2015
    Did you swap the ecu's and the TC's? If so, and you still can't get the light to change, then maybe two components are bad. I would start checking for power at the ecu's if you can verify ecu and TC's are good.

    I may be wrong, but I think I read in an old thread that someone found a broken wire that was causing them an issue.
     
  9. 355rockit

    355rockit Formula Junior

    Dec 1, 2010
    893
    San Marcos, CA
    Full Name:
    Vas
    #9 355rockit, Apr 26, 2015
    How are your 02 sensors?
     
  10. drbob101

    drbob101 F1 Rookie
    Owner Silver Subscribed

    Nov 26, 2012
    3,821
    Tinton Falls, NJ
    Full Name:
    Bob Ferraris
    #10 drbob101, Apr 26, 2015
    O2 sensors have nothing to do witn the SDL system.

    It is a stand alone , cat temp warning system. It has no effect on fuel trim.
     
  11. Rice-Racer

    Rice-Racer Formula Junior

    Jan 10, 2015
    252
    #11 Rice-Racer, Apr 26, 2015
    Similar issue here, my 1997 5.2, haven't driven car yet since delivered in February.
    I've ran it off and on weekly warm up to engine temp etc, driven 1/2 block and back for fun.
    Tonight, idled it for maybe 15-20 minutes, trying roof lowering. Then, got slow down light flashing. Shut down, waited 5 min then started, same flashing.
    I brought back in garage and shut power switch off, maybe try a reset of computer?
    It ran find when I test drive it before buying, cooler temps maybe 38-45 F out.
    Any reason for this?
     
  12. Rice-Racer

    Rice-Racer Formula Junior

    Jan 10, 2015
    252
    #12 Rice-Racer, Apr 26, 2015
    Last edited: Apr 27, 2015
    Update, I had a P1451 code, cleared it with scanner, car restarted and ran fine, no lights on.
    Only thing I did was change the muffler system to a Tubi Competition version from a Tubi ?? Version a few weeks ago, will check fuse on secondary air pump first, and see what happens when I can run it on the road.
     

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