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By YOUCANIC on May 7, 2019

Troubleshooting Fiat Check Engine Light Problem

In this guide, you will find instructions on how to diagnose Fiat check engine light yourself. 

Fiat Check Engine Light (CEL) may come on and stay on for multiple reasons.

In newer Fiat models such as late model Fiat 500, you will get  "HAVE YOUR ENGINE CHECKED" message on dashboard. 

The problem could be something as simple as a loose gas cap (fault code P0456) or an indication of another problem ranging from turbo boost issue, engine malfunction or misfire and even transmission problem.


The light itself does not provide much information other than warn you to get the car diagnosed as soon as possible.

Without reading the codes, it is impossible to know why your Fiat check engine light is on. 


The symptoms of Fiat check engine light vary.

Here is a list of symptoms you may notice when you Fiat check engine light comes on.

  • poor throttle response,
  • engine jerking when changing gears,
  • engine overheating
  • "high coolant temp, turn the engine off" warning,
  • engine stalls at idle or car is difficult to start. 

Sometimes you may not notice any performance issues at all.

If you don't notice any performance issues, you can continue to drive your Fiat but get it diagnosed as soon as possible. 

Common Problems

Some of the most common problems with Fiat such as 500 are listed below.

  • Poor fuel: Low-quality gasoline can trigger the CEL on Fiat vehicles
  • Turbo problem: Under boost pressure
  • Thermostat: Engine overheats or takes too long to reach operating temperature
  • Oxygen sensor: Increases emissions, a decrease in fuel economy. 
  • Mass air flow sensor: Often results in multiple codes and poor throttle response
  • Spark plugs: If one fails it will cause engine misfire and engine shaking
  • EVAP:   The EVAP emissions canister can fail triggering CEL and codes such as P0499. 
  • PCM: Failure changing spark plugs and wire harness does not fix the CEL. PCM replacement may be required.

Note that there are many more possible problems and hundreds of Diagnostic Trouble Codes (DTC) that can trigger the CEL on your Fiat.

Without diagnosing the vehicle it is difficult to know what the problem is in your particular case. 

How to diagnose Fiat Check Engine Light 

Instructions on how to read Fiat check engine codes yourself. 

What you will need


The following instructions work on Fiat vehicles manufactured from 1996 to present.


  1. Turn on Ignition. All your dashboard lights should be on. It is not necessary to start the engine. fiat cel on, turn on ignition
  2. Plug in your scanner into the OBD II port under the obd2 port location to diagnose check engine lightHere is how your Fiat OBD II port looks obd port locaitonThere is only one port like this. Sometimes it has a small cover, so you may not notice it easily. It may be hidden under the dashboard as well, which will require you to look carefully under the dashboard.
  3. Allow the scanner to communicate with your Fiat and detect the correct protocol. fiat check engine scanner


  4. Press read codes on your OBDII scanner or phone app to retrieve the codes. 

These instricuctions will allow you to read check engine codes on Fiat models such as Fiat 500, 500x, Abarth, Panda, Fremont, Viaggio, Ottimo, Ducato, Dublo, Tipo, Toro, Mobi, Argo, Punto, Panda, Croma, Seidici, Bravo etc. 

Read codes, what's next? 

It is strongly recommended to write down the code and research the problem.

Many owners get a code and start replacing parts based on the code alone.

Later they find out that the replaced part didn't fix the problem.

Don't start replacing parts without doing research on the code first. There are more than one problems that can trigger one code. 

Loose Gas Cap

fiat loose gas cap triggered check engine light

If you scan your Fiat and the code that you get is for a loose gas cap, make sure you tighten the gas cap until you hear two clicks.

You can also use an OBD-II scanner and clear the code once you tighten the gas cap.  If the CEL comes back to replace the gas cap.

If the CEL comes back on again, with a code for a small EVAP system leak, have a mechanic or your Fiat dealer would have to perform a smoke test to find the leak. 

You could have a leak at the detector evaporative system integrity module.

It is possible for a leak to develop at the filler neck as well. Without performing a leak test it is impossible to determine where the leak has developed.

Check Engine Light Flashing

If your Fiat check engine light is flashing, it means that the onboard diagnostic system (OBD) has detected engine misfire. In other words, one or more of the cylinders is not working properly.

It is not recommended to drive your Fiat if the check engine light is flashing. Driving your Fiat with CEL flashing can cause more damage to the engine and catalytic converter. 

As long as your Fiat check engine light is NOT flashing, it is usually safe to drive.

If you decide to drive your Fiat when the CEL stays on, you should carefully monitor dashboard warning lights and the engine temperature.

Do not drive if the engine is shaking or hesitates when pressing the gas.

Frequently Asked Questions

Yes, disconnecting the battery usually clear the ECU codes. By turning the check engine light off this way you will not fix the problem. If you believe the check engine light needs to be off, drive the car for a few days and the CEL will reset itself. The Onboard Diagnostic System in your car continually monitors your vehicle and will turn off the CEL if the problem is solved. If the problem hasn't been resolved, even if you disconnect the battery, the CEL will come back up again which can be as soon as you restart the car or up to a few days.

If check engine light is on, it will not pass emission inspection/smog test. If the light was recently reset with an OBD2 scanner or by disconnecting the battery, you need to drive the car for a couple of days for the systems to be ready for testing.

It could be because you are using an OBD2 scanner that does not support the protocol used in your car. Try a different scanner. Also, there may be an issue communicating with the ECU due to a damaged wire or ECU malfunction.

No. The check engine light is not the reason why the car doesn't start. If the car doesn't start, read the codes and maybe the CEL will give you a code that can help you diagnose the car. Clearing codes will not make your car start.

It may be just bad timing. An oil change is not going to trigger the CEL. Unless MAYBE a sensor got accidentally unplugged, disconnected or damaged during the oil change. Take your car back to the auto repair shop that changed your oil and have them diagnose the problem.

No, the CEL should not turn on after routine maintenance. If you modified your engine, transmission, exhaust, intake, fuel system or other systems it can affect engine and emission control system, causing check engine or service engine soon light to come on. CEL should not come on if you changed tires or tire size.

Drive the car for a couple of days and allow the ECU to reset itself. If the CEL still remains on, read codes.

The check engine light is trying to tell you that there is a problem with your engine. It could be low coolant, stuck thermostat, transmission not shifting. Figure out why your car is overheating first and address that problem. DO NOT CONTINUE TO DRIVE IF YOUR CAR OVERHEATS.


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