2015-2017 Fiat 500 Engine Control Module: Misfires, Programming, and Replacement
This guide covers the common failure points, programming requirements, and replacement costs for the Engine Control Module (ECM) in the 2015-2017 Fiat 500 with the 1.4L non-turbo engine.
- This ECM fits the 2015-2017 Fiat 500 with the 1.4L non-turbo engine, identified by the 8th VIN digit 'R'.
- Programming is ALWAYS required. A replacement ECM must be programmed to your car's VIN to disable the immobilizer and function correctly.
- The most common failure symptom is a severe engine misfire with a flashing check engine light, often caused by an internal ECM defect.
- Before replacing the ECM, check for simpler issues like a loose battery terminal or blown powertrain-related fuses.
Is This The Right Part For My Fiat?
This Engine Control Module (ECM) is specifically for the 2015-2017 Fiat 500 equipped with the 1.4L MultiAir non-turbo engine. The easiest way to confirm you have this engine is to check the 8th character of your Vehicle Identification Number (VIN). If the 8th digit is an 'R', this is the correct engine for this part. The most common OEM part number for this module is 05150956AC or 5150956AC.
Warning: This ECM will NOT work for the Fiat 500 Abarth or Turbo models, which use a different engine and engine computer.
Symptoms of a Failing Fiat 500 ECM
A failing ECM in the Fiat 500 often presents with very distinct and frustrating symptoms. The most common issue reported is related to internal failures that affect the ignition system.
- Engine Misfires: The most prevalent symptom is a sudden engine misfire, which can occur on one or multiple cylinders. This often happens when the car has warmed up or is driven at speeds over 40 mph.
- Flashing Check Engine Light: A misfire will almost always trigger a flashing Check Engine Light, indicating a severe issue that could damage the catalytic converter.
- Limp Mode: The vehicle may enter 'limp mode,' drastically reducing engine power to prevent further damage.
- Stalling or No-Start Condition: The engine may shut off for no reason or fail to start intermittently or entirely.
- Loss of Communication: In some cases, a diagnostic scan tool may not be able to communicate with the ECM, which is a strong indicator of module failure.
- Associated OBD-II Codes: A failing ECM is commonly associated with codes for cylinder misfires (P0300, P0301, P0302, P0303, P0304) and ignition coil circuit malfunctions (P0351, P0352, P0353, P0354). One potential cause is a faulty ignition coil pack shorting out and sending a high-voltage spike to the ECM, damaging it internally. 🎬 Watch: How to test your coil packs and diagnose ECM misfires.
Pro Tip: Before condemning the ECM, always check the basics. A loose battery terminal can cause symptoms that mimic ECM failure, including a no-start condition and communication errors. Also, inspect the related fuses and the ECM power relay (T09 in the under-hood fuse box) 🎬 See this video to locate and replace the ECM power relay. to ensure the module is receiving power.
Known Issues, Recalls, and Technical Service Bulletins (TSBs)
As of early 2026, there are no active safety recalls from the National Highway Traffic Safety Administration (NHTSA) for the Engine Control Module on the 2015-2017 Fiat 500 with the 1.4L non-turbo engine. Recalls you may find for Fiat vehicles often pertain to the larger 500L model or other modules like the Tire Pressure Monitoring System (TPMS).
A widely reported issue on forums and by rebuilders is a potential manufacturing defect within the ECM itself that makes it prone to failure, specifically causing the misfire conditions described above. Some sources claim that even new replacement units from the manufacturer can eventually fail in the same way, making a high-quality remanufactured unit with corrected internal components a potentially more durable option.
Buying a Used Engine Control Module
Purchasing a used ECM can be a cost-effective solution, but it comes with critical requirements. You cannot simply swap a used ECM from another car and expect it to work.
Programming is Mandatory: The ECM is tied to the vehicle's anti-theft system (immobilizer) and is programmed to a specific VIN. A used module must be 'virginized' (wiped clean of its original vehicle data) by a specialist before it can be programmed to your car. After installation, a dealership or a qualified independent shop with Fiat-specific software (like wiTECH) must perform a 'Proxi Alignment' procedure to introduce the new module to the car's other computers.
What to Look For:
- Verify the Part Number: Ensure the part number on the used module (e.g., 05150956AC) matches your original exactly.
- Inspect for Physical Damage: Check the connectors for any bent, corroded, or damaged pins. Look at the casing for any signs of being pried open, water intrusion, or heat damage.
- Choose a Reputable Seller: Buy from a seller who guarantees the part is in good, working condition. Many online vendors sell used or remanufactured ECMs that are pre-programmed to your VIN, offering a 'plug-and-play' solution. This is often the easiest path for a DIY replacement.
Cost Comparison for a 2015-2017 Fiat 500 ECM
The cost can vary significantly depending on the source of the part and labor rates. Here is a general breakdown:
| Part Type | Estimated Cost | Notes |
|---|---|---|
| New OEM | $350 - $480 + $100 Core Charge | Purchased from a Mopar dealership or online OEM parts retailer. |
| New Aftermarket | Not Widely Available | Major aftermarket brands like Dorman and Cardone do not commonly list new units for this application. |
| Remanufactured / Pre-Programmed | $250 - $500 | Often sold online as a 'plug-and-play' solution, programmed to your VIN before shipping. |
| Used OEM | $80 - $250 | Sourced from an auto recycler. Will require additional cost for programming. |
| Shop Labor (Installation & Programming) | $150 - $500 | Typically 1-2 hours of labor. Dealer rates are often higher than independent shops. |
ECM Location and Replacement Overview
Replacing the ECM is a relatively simple task for a DIYer with basic tools. The module is located in the engine bay, mounted to a bracket next to the battery.
- Disconnect the Battery: Using a 10mm wrench, disconnect the negative battery terminal first, then the positive. This is critical to prevent electrical damage.
- Remove the Battery: Unbolt and remove the battery and potentially the battery tray to gain clear access to the ECM.
- Disconnect the ECM: The ECM has two large electrical connectors with locking levers. Disengage the locks and carefully pull the connectors straight off the module. 🎬 Watch this step-by-step walkthrough of the ECM removal and replacement process.
- Unbolt the ECM: Remove the bolts holding the ECM to its mounting bracket.
- Installation: Installation is the reverse of removal. Mount the new ECM, reconnect the electrical connectors, reinstall the battery, and connect the positive terminal first, followed by the negative.
Important: If you did not purchase a pre-programmed 'plug-and-play' unit, the vehicle will not start until the new ECM is programmed by a professional.
Frequently Asked Questions (FAQ)
Do I have to take my car to a Fiat dealer for programming?
Not necessarily. While a Fiat dealership is a guaranteed option, many independent auto repair shops that specialize in European vehicles or auto electronics have the necessary tools (like wiTECH or a compatible J2534 device) and software subscriptions to program the ECM. You can also use a mail-in service to have a replacement module pre-programmed to your car's VIN.
Can I drive my Fiat 500 with a bad ECM?
It is not recommended. If the ECM is causing severe misfires, stalling, or unpredictable behavior, the vehicle is unreliable and potentially unsafe to drive. A flashing check engine light indicates a severe misfire that can quickly destroy your catalytic converter, leading to a much more expensive repair.
Will a used ECM from the exact same year and model work without programming?
No. The ECM is linked to the original car's immobilizer system and VIN. A used ECM must be professionally 'virginized' (reset to a factory state) and then programmed specifically to your vehicle's VIN to function.
Could a bad fuse cause my ECM to seem dead?
Yes. Before replacing the ECM, check the related fuses in the under-hood fuse box. Fuses F09, F11, F17, F18, and F22 have been identified as being related to the powertrain control module. Also, check the main ECM power relay, T09.
Helpful Videos
Technical Specifications
OEM Part Numbers: 05150956AC 5150956AC P68240362AF 68240362AF
Fits 1.4L MultiAir I4 16V non-turbo engine (VIN 8th digit 'R').
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Fiat 500:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is This The Right Part For My Fiat?
- Symptoms of a Failing Fiat 500 ECM
- Known Issues, Recalls, and Technical Service Bulletins (TSBs)
- Buying a Used Engine Control Module
- Cost Comparison for a 2015-2017 Fiat 500 ECM
- ECM Location and Replacement Overview
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off