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EU 355 M5.2 SLOW DOWN

Discussion in '348/355' started by Ricambio, Oct 30, 2019.

  1. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    Hi,

    here's another SLOW DOWN issue. I recently fixed a EU 355 M2.7 with one SLOW DOWN light (bank 2) by replacin both CAT modules with the aftermarket/revised units that a member here makes and sell with great results, the car never failed again, very happy.

    Now I have this EU M5.2 that was heavily serviced and many things new replaced (somewhat restored the car) and was almost ready to delivery for his owner from the nowhere the SLOW DOWN light came up and won't turn off, it's solid (doesn't blink at all), even in cold starts does light up. No check engine.

    So, we had another EU 355 M2.7 next to this car and grabbed the CAT modules just for test (both are interchangable) and SLOWN DOWN light still ON, grabbed the old ones I replaced from other EU 355 M2.7 (faulties) and still the same.

    Then we checked all the DME/wiring harness for continuity and clean contacts, checked the thermocouplers values and all 03 cars are about the same paramters in same "cold" weather so we discarted the sensors.

    As I know (i might be wrong though) since are EURO version, these cars doens't have a OBD1-2 connectors and can't be diagnosed with a scanner or SD tool, they seem to work like the old BMW e30 M3, they have the roundconnetcor for the reset oil service tool and scanner, but only can be scanned the regular e30's not the M3, so you must check values of sensors and apply certain tricks to troubleshoot the systems.

    Anyhting else to look for or check, please let me know!

    Thanks
     
  2. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    Forgot to mention, even with the SLOW DOWN light ON, I went for a spin and the engine power is intact,in other words, not affected unlike the M2.7 car that once the light comes up, you feel like half engine is dead and barely can move the car.
     
  3. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
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    "Ricambio", all 5.2 cars can be scanned with an SD-1 tool and Euro cans can be scanned with a regular OBDII tool using a 3 pin adaptor (behind the left hand seat) with the immobiliser turned off. Look for a Fiat 3 pin OBD2 adaptor or make one yourself.

    I assume the Euro car doesn't have a third thermocouple TCU, so I guess there is no chance that the wiring was mixed up. I guess that just leaves the thermocouples themselves and wiring to the ECU. Perhaps one of the thermocouples was damaged during the service?
     
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  4. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    #4 Ricambio, Oct 30, 2019
    Last edited: Oct 30, 2019
    Thanks for that. Although, I don't have SD here, I do have generic scanner (Autel) which works great in other Ferrari vehicles we have fixed. I will give a try for the "Fiat 3 PIN" connector or fabricate one here in the shop and give it a try.

    Will report back

    EDIT: Will this work?
     
  5. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
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    Yes, that's similar to what I use. A really cheap solution. I wired the red and black power leads to a cigarette lighter adaptor.
    Just plug it into the 3 pin plug near the Motronics ECU. Turn on the ignition and turn off the immobiliser. Use generic BMW /Audi selections on your scanner if Ferrari-specific selections don't work. We can help you with the codes.
     
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  6. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    Just ordered the cable, I will wait to get it and try to scan it and see what I get. I uess the TEVES ATE system / airbag is not possible to read with a generic scantool with any special adapter/connector like this right? ABS I know the sequence to diagnose it though.
     
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  7. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
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    Correct.
     
  8. drbob101

    drbob101 F1 Rookie
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    Nov 26, 2012
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    Check / change the thermocouples. They are often faulty and trigger SDL.
     
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  9. wbt

    wbt Karting

    Nov 28, 2014
    114
    New Zealand
    As drbob says, a thermocouple failed open circuit can show a solid slow down light, although both cylinder banks still operate normally. I discovered this during development of my cat ECU units as it was a behaviour I needed to replicate.
     
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  10. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    I will check again the thermocouplers and see the wires and the sensors themself , but last time we did, they were fine and the light will still keep on with other TCU (sp?) but not the sensors swaped.
     
  11. yelcab

    yelcab F1 Veteran
    Consultant

    Nov 29, 2001
    9,304
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    Mitchell Le
    I believe you can drive the car with a solid SDL for about 30 miles and then the engine will shut off the offending bank. At least that is how the US models work in 5.2 DME
     
  12. johnk...

    johnk... F1 Veteran
    Owner

    Jun 11, 2004
    7,446
    New England
    Based on experience I would not recommend that. If the light comes on, pull over. Figure out the problem before you damage the cat or something more serious. If the cat is really overheating it's a signal of a more serious problem, like a very rich condition.
     
  13. wbt

    wbt Karting

    Nov 28, 2014
    114
    New Zealand
    What is happening in your description is the cat is slowly overheating, first the light flashes, then if it heats up further it stays on solid, further heating again then it cuts fuel flow to the offending bank to self protect. This is the warning system doing its intended job. Never ignore the light or drive with it on! Often it's the common ECU/thermocouple electrical issues but if the cat is overheating for real, then your expensive cats could become toast or worse the fire risk becomes very high. Get new ECU's in there, swap out the thermocouples and drive with 100% confidence that the warning light system is working properly. Small cost for peace of mind.
     
  14. Qavion

    Qavion F1 Rookie

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    Thermocouple ECUs have already been tried (from a known good car). All that remains are the cats and thermocouples. The ECU seems to have deemed that there is no fault (no CEL), but a temperature problem. Without a CEL, will the ECU still identify which thermocouple or cat is causing the issue (using an OBD2 tester)?

    Ricambio, have you measured the actual cat temperatures using an infrared thermometer?
     
  15. drbob101

    drbob101 F1 Rookie
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    Nov 26, 2012
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    As I have advocated many times, if you really want to know what’s going on and fix these SDL issues once and for all, tap the outputs of the SDECUs and drive around with a DVOM in your lap and watch the real time voltages coming out of the SDECUs

    This is how I got involved in this issue. I diagnosed a faulty, intermittent thermocouple that was only visible by this method.

    So replace parts, including thermocouples, or tap the SDECU outputs and know what your dealing with.
     
  16. m.stojanovic

    m.stojanovic Formula 3
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    Dec 22, 2011
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    In Ricambio's case, since the SDL comes on immediately upon start-up and stays on, he doesn't need to drive the car but just measure the output voltages of the SDECUs with the ignition on. The normal voltage is about 0.5 V. If the voltage on one of the SDECUs is about 5 V, the Thermocouple for that SDECU is bad or the Thermocouple wire, or its connector, has an open circuit.
     
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  17. drbob101

    drbob101 F1 Rookie
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    Nov 26, 2012
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    I have personal experience with this.

    The faulty output was only visible when the engine was running. The micro vibrations/movement of the assembly caused and displayed on the DVOM voltage spikes that initiated SDL

    It may be visible on idle alone or when driving but it may not occur on static engine off observation.

    I have video of the DVOM display showing this somewhere.
     
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  18. Beetle

    Beetle Formula Junior
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    Apr 10, 2013
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    Paul, Australia
    Drive the car and use a thermal heat gun pointed at each cat, or in that vicinity. After 5 mins you will soon see a difference if there is an issue. If not you may have a gremlin.
     
  19. emac

    emac Formula Junior
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    Sep 14, 2014
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    upstate SC
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    ernest
    Listen to what DrBob says. I had problems with mine when I first bought my car and he helped me diagnose and fix mine. If he is still making the thermocouples just get all new ones from him to make sure that isnt the issue. They arent very expensive.
     
  20. Qavion

    Qavion F1 Rookie

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  21. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    #21 Ricambio, Nov 22, 2019
    Last edited: Nov 22, 2019
    Thanks guys for the feedback and suggestions. I'm sorry that replied late as been very busy and was waiting to get delivered the 3 PIN FIAT/OBD2 cable but it never showed up, probably a scammer shop in California. So went to purchase a similar cable from eaby and still waiting to arrive, hopefully with my Autel scanner can scan it when i get the coverter 3 PIN cable.

    Speaking of issues, the other F355 euro M2.7 that i replaced both CAT modules with the updated version that is sold from New Zeland (Technistrada as quoted)) was working top but owner left stranded after the car didn't want to start, flat bed into the shop and it did start perfect and no issues so far. Also has the suspension light comming and going off and the top of that it did blink once the 1-4 CAT overhating light uuurggggghh! These lovely cars.....

    I will report when I get the chance to try to scan it. We have checked pretty much every connection and the thermo couplers in the euro M5.2 F355 and used the old CAT modules that we replaced with the new ones from Technistrada supplier in the M2.7 and still solid red light.
     
  22. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
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    Good to hear that the Technistrada modules were not the cause. I see they also produce relatively inexpensive thermocouples now.

    Sorry to hear about your adaptor problems. They are selling for a crazy U$3.30 with free local postage here in Australia. Of course, they have to be made in China at these prices, but I still don't know how they make a profit. It takes a few weeks for them to arrive, however. Don't panic.

    With intermittent suspension problems, you may need to send your customer to someone with a Ferrari SD1 tool to help with diagnosis. It could take hours chasing problems and I'm sure the customer won't be too happy about that. You might be lucky and find a broken rear suspension actuator or broken cog on the shock absorber, but if no luck there, you have to start pulling the car to pieces. To access the front suspension actuators, you may have to remove the jigsaw puzzle of front luggage compartment liner pieces. The pieces are somewhat fragile. I had a dozen cracks in my liner pieces before I found a rare new set.
     
  23. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
  24. Qavion

    Qavion F1 Rookie

    Feb 20, 2015
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    Just to confirm, your ignition was on and your immobiliser was turned off? (to activate the Motronic ECU)

    Did you try selecting a non-Ferrari vehicle? Fiat? Audi?
     
  25. Ricambio

    Ricambio Rookie

    Dec 30, 2016
    37
    Yes, inmobilizer off (engine could start) and IGN ON. I did try with FIAT (brand) scannin and nothing...it start to scann a bunch of different modules but still won't find any.

    While scanning the M5.2 (you have seen in my previous post) if I dissconnect the OBD2 cbale from the FIAT adapter, it will still keep scanning the module until it reach 100%, so in other words it doesn't recognize a break in the communication while scanning, but it might not be important though.

    I'm clueless what else can i do for the slow down light
     

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