Hi, I have had 2 fiat 500's 2011-2015 that go into limp mode when I drive over 70-80mph. The first indication of a problem is stop/start unavailable lights come on the dash, then the engine management light comes on. If I restart the car, it resets and drives fine until I do a high speed again. Any similar experiences or ideas please. Thank you.
Technical Limp mode past 70mph
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Limp mode past 70mph
You say “I have had”. Does that mean you no longer have the cars? If you do still have one or both, what engines please?
I still have the cars, they are 1.2 8V engines
This is a very common Fiat 500 issue and the symptom order you describe is the big clue:
Stop/Start unavailable → then engine management light → limp mode at sustained high speed.
On these cars that sequence almost always points to a charging/voltage control problem, not a random engine fault. At higher speeds the ECU monitors alternator output, battery condition and voltage stability very closely. If voltage goes out of range, the ECU disables stop/start first, then throws the EML and limits power.
The most common causes are:
Weak or incorrect battery (especially non-AGM)
Failing alternator/regulator
Poor engine or body ground
Battery current sensor (IBS) issue.
Quick checks:
Measure charging voltage at idle and at motorway speeds
Check battery age, type and state of charge
Inspect and clean main earth straps.
Restarting clears it temporarily because voltage stabilises again until sustained high load/speed brings the fault back.
Get it scanned with Multiecuscan or dealer diagnostics and look specifically for voltage or charging-related faults, generic readers often miss them.
Stop/Start unavailable → then engine management light → limp mode at sustained high speed.
On these cars that sequence almost always points to a charging/voltage control problem, not a random engine fault. At higher speeds the ECU monitors alternator output, battery condition and voltage stability very closely. If voltage goes out of range, the ECU disables stop/start first, then throws the EML and limits power.
The most common causes are:
Weak or incorrect battery (especially non-AGM)
Failing alternator/regulator
Poor engine or body ground
Battery current sensor (IBS) issue.
Quick checks:
Measure charging voltage at idle and at motorway speeds
Check battery age, type and state of charge
Inspect and clean main earth straps.
Restarting clears it temporarily because voltage stabilises again until sustained high load/speed brings the fault back.
Get it scanned with Multiecuscan or dealer diagnostics and look specifically for voltage or charging-related faults, generic readers often miss them.
The next question I would ask is have either of these cars recently had a new cam belt fitted?
Thank you so much for that detailed response. I will do those investigations and report back
Not a recent change but do you suggest a proxy alignment if they had been changed recently?
Oh ok thank you
The Panda Nut
Nutty about Pandas Infected by Panda virus and OPD
Ive had a Panda (2009 169) doing this. The 319s were all lifeless too when bought. I dont know what exactly was causing the 169 issues but it was permanenty fixed by cleaning MAP sensor, cleaning the accumulated gunge out of the manifold, cleaning the throttle body, changing the plugs leads and coil, cleaning the VVT solenoid. You could guarantee at 70mpg it would hit a wall, the EML would come on and it would report a fault misfire on 1 & 2. AT about the same time I replaced the thinner of the two breather tubes from air box to manifold which was cracked. I suspect a poor seal of airbox to throttle body may also have been involved. I cleaned the rubber seal and applied silicon so it was re stuck to the throttle body. As I did the whole job lot in one go I dont know which it was. I have found that if these jobs are not done and maintained the performance of all teh ones I have had is badly dented. They just become flat and lifeless. Our oldest one is 2014 at the moment and that car truly sparkles, its a total gem to drive. The VVT seems to stick if the car isnt driven hardish regularly. The amount of muck washed from the VVT solenoid was astounding. Washing followed by bathing in clean oil for half an our prior to refitting has really made a big difference. You can feel the VVT work at 3600 rpm. I now make sure the car is driven at 4500 rpm for 20 to 30 seconds a few times at least once a fortnight. The affect of doing this has been profound. The 1.2s are all now quite brisk for 69HP. They had become like slugs prior to treatment. The beauty of this is apart form the coil pack these are cheap things to do and not difficult or time consuming. I hope this may help.
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Never do that! Never put silicon there. It can easily be sucked in while accelerating and that is not good at all. If there is a problem, just put new seal.
The Panda Nut
Nutty about Pandas Infected by Panda virus and OPD
I dont agree. The seal is u shaped and a thin bead into the U effetcively sticks the edge to the throttle body when its pressed back on, exactly as it was when new. There should be no excess. It hold the seal correctly in place so it stays put when the airbox is removed for maintenance. The gasket / grommets on the throttle body are done this way when new. Over several years oil and muck degrades the silicon and the seal comes off with the airbox. Degraded dealant in the u shaped deforms the seal and it will not sit true if just put back. It is fiddly turning the seal inside out and getting the original sealnt off but it seems t be worth the effort. Fitted back loose as most are they move around and wear out fater as well as not doing the job they are there for, then becoming a problem. A small amount of silicon on a properly cleaned grommet plumps the seal amd ensure it is more effective. I would wipe off excess although this is clearly not done at the factory. It seems to take 5 to 7 years for the airbox seal to work loose after which inaction leads to poor running in my experience.
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Wow!! Thank you so much for this information. I will endeavour to follow and report back. Thank you
I see what you mean. A tiny bead inside the U-shaped seal can help it stay in place, especially on older seals where the original sealant has degraded.
Just be very careful, any excess silicone wiped off, and nothing should touch the throttle bore or be exposed to airflow. Otherwise it can get sucked in and cause problems.
So yes, done carefully it’s a pragmatic fix, but for anyone unsure, replacement of the seal is still the safest long-term solution.
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If the car goes in to limp mode over 70mph...then don't drive more than 70mph. You cannot legally in the UK anyway. Issue solved. Sorry. I couldn't resist
Did the car run fine over 70 then suddenly developed the issue, or, did it run fine but was rarely driven over 70?
Classic cam belt problem
Classic cam belt problem
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The Panda Nut
Nutty about Pandas Infected by Panda virus and OPD
I know ours was OK below 70 but this happened every time you tried to go 70+ which.... for the benefit of the jokers ha ha, is 63mph. I used to tell my daughter to stay under 70 for the good of the engine. Allthe things I listed have the potential to cause the issue but I guess I suspect the coilpack may have been failing under load. I think I still have the old one as it worked normally and may not have been the cause.
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