RS 275 shuts off randomly

Discussion in 'Electrical & Interior - Security, ICE, Wiring Loom' started by deniru, Sep 13, 2023.

  1. Hi everyone,

    Fresh owner of an 2015 RS Trophy which has one of the most absolute weird symptoms I've encountered in a car.

    So the car essentially dies randomly while driving and won't start or will die again shortly after.

    Absolutely no issues with cold starts, engine power is fine, but after around 30 mins or so of usage, the engine stops, I still have dashboard/radio lights, no errors. If I lock the car and let it be for couple of minutes it usually starts again but will just die on me again within minutes or seconds (it's a lottery).

    As a bit of context, sometimes when the car does not die on me and I stop the engine voluntarily, the dash dials remain in the same position as if the car would be turned on (RPM needle at ~850 RPM and fuel tank needle). What I would do is to reinsert the card and the dash would reset to a zero position , else, if I would leave it be and lock the car, the dash light and needles would stay lit which most likely would eat up the battery over night.

    No errors on an official Renault tester, checked all fuses, previous owner changed battery and the "Unite Control Habitaclé" last year, problem persists.

    Initially I went to a mechanic since I was suspecting the fuel pump but the car is not lazy, mpg is normal, he was suspecting the immobiliser and sent me over to a guy who was specialized in Renault computers and he said that the ECU, UCH are fine and since there are no remaps installed on it and no errors in the tester, symptoms indicate a sudden loss of power preventing the ECU to log anything.

    I also have the auto start/stop function disabled and he said this shouldn't impact or have this behaviour.

    Tonight, luckily I had just parked the car, but haven't turned it off to let the turbo cool off for a sec and got out of the car to get my stuff from the trunk in the meantime. I noticed the number plate light flickering like Christmas tree and few seconds later car did its thing and engine died. May this be related to the issue I'm having?

    Forgot to mention, when I'm pressing the start button after it dies, it does nothing. It doesn't try to turn the engine over, doesn't try to charge the fuel pump, it's like I'm not doing anything.

    Oh and one time the car died on me on a traffic light, I left the card inserted and not pressed anything (car was in neutral, I was busy calling someone to pick me up) and literally turned itself back on without me pressing any buttons/pedals.

    It's like it's possessed... I will preventively change the camshaft and crankshaft sensors (I had another 1.6L Mk3 Meggy which had a similar issue) but in that case the starter was trying to crank it and won't die on me once engine runs so it's not the same situation.

    I will book an electrician soon, but just wondering what else can I ask him to check/go after besides wiring as I'm running out of ideas and tired of just spending money on "I don't know's".

    Very not fun having a 1400kg piece of metal with no engine running at 60kmh...

  2. Seeing an auto electrician is the right move - I suspect it is an earthing issue ("xmas tree reference, tacho not zeroing, etc)

    Not sure how hands on you are but I've attached a few drawings showing location of the various earthing points - anything shown with a code starting with "M" is an earth.

    It may be as simple as a welded earth stud nut being loose causing these issues. Trace the locations thru and see if all are tight, as well as the crimped wire lugs. Some are easy to see/access, others are pretty difficult.

    Also I noticed that you mentioned accessories staying on etc overnight - make sure all the battery negative connections and crimped lugs are all tight, including the one on the body stud connection, and not just around the battery.

    Good luck

    Attached Files:

    autronix likes this.
  3. also check main relay / relays
  4. thanks a lot @Zoto and @autronix really helpful!!!

    update so far: went to a mechanic to change the oil and filters and asked to tighten the gearbox earth while at it, wasn't loose but it got tighten a bit more so i had my hopes up, checked and cleaned the relays - seems the stuck tacho issue is now gone, they go down when shutting off the car myself or itself. (around 10 stops and no issue, usually 4 out of 10 stops needed me to reinsert the card to reset them to 0 position previously).

    car still died at around 30 min mark this night, behavior is a bit different now. died while driving (as expected, kinda used to driving on sidewalk lane side at this point) what is changed is that the engine light flashes 2 times (it dies the first time and i think the ECU tries to restart the car but it just doesn't and thus the second flash), dash stayed lit, being at night and in a dark area i could clearly see there wasn't any difference in dash intensity and also headlights were working fine.

    Everything electronic was working normally, the car just won't start (i even had power steering - not sure how, the engine was definitely off, was driving with the windows down and could clear if the engine would have been running).

    Same old story, pressing start button, nothing happened. Got out of the car, closed it, re-opened, got back in, dials and everything else were working fine, just won't start (no sound of the fuel pump loading up, it's as i'm not pressing the button).

    Got back off, let it be for 15 min, got back in, it started no probs, then died within seconds - power steering was working which helped parking it better. Let it be for another ~45 mins, got back in, started with no issues, got home (~10 min drive) as nothing happened.

    No errors, nothing, but having the engine light popping up before cutting out is leading me to change the lambda probe sensor which i will order soon and makes me circle back to maybe a fuel pump/filter issue which I initially suspected. Again, all of my expertise and self-suggestions come from having owned the 1.6 L 16v 110hp 2009 Coupe Meggy which had its fair share of abuse in 8 years of ownership and having to go through the quirks of identifying what was the issue with what sensor so I'm inclined to believe that the real deal of its version might still have inherited bit of these quirks but the behavior and cars are ultimately not the same although the symptoms are sometimes comparable.

    Since the first events, it's sort of an improvement as the car dies around 30 min mark regardless of temperature (thought this could be the issue as in an overheated ECU - ~35c in daytime, but night time is ~16c, still dies within the same time frame). Doesn't care if you drive it like an old lady or redline it, doesn't care if you are driving or just idling in a parking lot, all it needs is a working engine to shut off around 30 min of usage. If it has a coin slot where I need to put some spare change to keep having fun with it for extra time let me know...
  6. Post on the Megane forum on Facebook, they are quite active over there. Let us know how you get on.
  7. Sporadic faults are the worse to trace.
    Different car but similar symptoms was an earth split (where the big cable is soulder to two smaller earth cables) that was dodgy. It only happened when the car was hot and radiator fan kicking in. Not sure if the Mégane RS uses this kind of harness though.
    Anyway from what you are saying, it definitely sounds like a component that doesn't like to warm up.
    Maybe try to leave the car home, let it warm up a little bit and wiggle the engine harness to see if you can replicate the cut off. Might sounds simple but it's free to try by yourself .
    Best of luck
  8. I didn't read all of post but I know the solution for your problem... ECU is dead. I have had same problem with mine I changed ecu and that fixed all the problems.
  9. Did you manage to fix the problem?.
  10. not yet, though the problem looks 99% like what was reported here:

    However, I stopped having issues with the car completely since the temperatures have dropped as of November and the max outside temp I drove wasn't higher than 15c.

    I went to few other places to check and try to diagnose the problem and so far I've been only proposed as a permanent solution to replace the ECU, BCM and UPC however I'm not really keen on doing that just yet since the BCM and UPC have been replaced by the previous owner (he had the issue too, however per his words it didn't occur that often) and after replacing those two the problem stopped for a year or so and then it came up once and had it sold over to me.

    The issue with the newly replaced BCM and UPC is that they might not have been programmed properly by the Renault dealer he went at so whereas the parts are relatively new, they could still be a culprit. Previous owner has also shut off the auto-start-stop as he thought that's what could cause it. I have reactivated it (though the physical button does not work anymore) and it works absolutely beautifully now in cold weather as intended - stops the car nice when it needs to or it doesn't if in Sports mode.

    After months of research and considering we do have relatively high temps here (summer day is around 42c, oil temp was reaching close to 98c per the monitor reading) I do think this is temperature related and that the ECU might be faulty but I'm not happy with the other components too. I have agreed with a Renault technician to get in touch once the problem will come up again since at the time he saw the car it was quite cold outside 5c temp and the car performed absolutely normal. It also makes sense that most of the times the car was dying was at stop lights or relatively low speeds because it was getting hotter enough to trip whatever it's tripping.

    Normally now at 5c outside oil heats up to 72c and stays around that if driven normally or redlined only in 1-2-3 gears. I could at most get it to 86c after 15 mins of driving at ~240kmh or averaging 150kmh but again, the car is magnificent and the intake temp stays anywhere close to 30c whereas in summer the intake temp was close to 70c and oil casually over 90c.

    I was told the BCM rarely fails and if it's anything that could go bust it could be either ECU or the UPC but first point would be for the car to start acting nasty again (which i'm fairly confident it will around March/April when we will get over 20c or so) and they will try to re-write the BCM, UPC and to update the ECU as it is on the very first factory version. If that doesn't work, I will replace the ECU and if that doesn't solve it either I will replace once again the BCM, UPC and pretty much closing the loop of the first suggestion of replacing everything.

    Alternatively to having it reprogrammed and dealing with Renault again I could also go on the route of getting a starter kit, but was told apparently I need an exact 275 donor as a 250 or 265 won't work. I thought the power output differences are only from software (as if I use a custom map of 310hp won't matter if I'm coming off an 250 or 275) but at least from what I was told, there are differences in turbo and other mechanical bits.

    The thing is I'm pretty sure I have more chances meeting the person who assembled this car if I go on holiday in Spain than ever finding a 275 full starter.
  11. If you really think heat is a factor, try heating up the ECU. I use a hairdryer at work for this kind of thing.
    Heat = hairdryer
    Cold = chuck the thing in the fridge
  12. ianplymouth

    ianplymouth RSM Club Member

    The face lift 265's and the 275's don't have the cooling for the ECU as the 250's do, i have heard of others that have had a problem on the later cars have there ECU's overheating, just a thought
  13. quick update: car started acting up on its own given the recent high temps and I finally gave in and put my faith and went to the dealer. They have identified the ECU mass connector loose and per their words the ECU itself has been tinkered with as the seal was broken. They recommended full ECU replacement which I agreed to.

    950 EUR and 3 weeks later the car seems to be fixed though I have managed to drive only around 100KM, consider the past behavior it would have stopped by now given the driving conditions. So yeah... ECU replacement.

    Just wanted to thank everyone for their thoughts and suggestions!
  14. that was EMS3125? what dealer replaced it? Serus?

    many thanks
  15. it's EMS3110 (took a picture from the bay directly - manufacturer code matches repair paperwork I've received 237105248R).

    Yes, I replaced it at Serus, very positive experience overall and they kind of won me as a customer, I plan to do the regular service at them too, if the work quality is the same, I don't mind paying the dealership premium knowing the car is on good hands.

    update 2: almost 2000 kms since replacement, still no acting up. Had to take the car last week since the AC on my old faithful daily Mk2 Meggy is dead and we had a heatwave of 38c here. After 1.5h in rush hour gridlock Mumbai traffic like the car performed flawlessly despite 42c outside temp and 70c intake temp, so at this point I'm 100% confident the problem is fixed. Turning off the car sounds a bit rough when in Sport mode (comparing here with my ex-Mk3 Meggie 1.6L) so I'm always switching to Normal mode before powering off, but at this point I'm just nitpicking, the car definitely works like a charm.

    Attached Files:

    • ECU.jpg
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  16. from today I can offer EMS3110 and EMS3125 cloning , full boot 1:1 image transfer

    no immobilizer tampering (immobilizer active)
    no adaptations needed (cluster , UCH , BCM , etc etc)
    full data flash + eeprom transfer (boot password not needed)

    based in EU

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