Fiat IAW 5NF ECU Malfunction
The Fiat Stilo, manufactured between the years 2001-2008, along with the Fiat Doblo (2000-2010), Panda (2003-2011), and Punto (1999-2010) are all fitted with the commonly failing IAW 5NF engine ECU, produced by Magneti Marelli.
What goes Faulty?
The IAW 5NF ECU is prone to developing multiple faults, which will cause symptoms such as an illuminated engine management light, erratic throttle response that leads to acceleration failure, and instances of the Fiat Stilo randomly cutting out and intermittently failing to start. In response to these faults, the Fiat Stilo will be forced into limp home mode, an emergency safety measure that restricts the engine’s performance, preventing the vehicle from rising above 2000 RPM.
How to Diagnose 5NF Faults:
If your Fiat is having difficulties with constant cutting out, non-start and no acceleration, the ECU is malfunctioning. To diagnose these faults diagnostic equipment can be used to scan the vehicle for any stored fault codes. However, it is common for diagnostics to fail in establishing communications with the faulty ECU, preventing it from reading stored fault codes.
Provided diagnostics can establish a connection to the ECU, it will likely reveal one or more of the following fault codes:
- P1687 – Motorised Throttle Fault/Signal Implausible
- P0220 – Throttle Position Circuit
- P1221 – Throttle Position 1 Circuit
Sourcing a Replacement 5NF ECU:
There is currently no remanufacturing solution for this 5NF ECU malfunction. However, this ECU can still be obtained through buying a replacement unit, which are available from specialists such as 1st Choice here: https://www.1stchoice.co.uk/.
Decoding & Reprogramming the Replacement Fiat ECU:
Please note that these ECUs are coded to each individual vehicle, therefore, the unit will need to be reset and reprogrammed to your particular vehicle. If the ECU is not decoded properly, the immobiliser will be activated which will prevent the engine from starting.
Common Failure symptoms:
- No Acceleration
- Limited to 2000 RPM
- Cutting Out
- Intermittent Non-Start
- No Communication the ECU
Common fault codes:
- P1687 – Motorised Throttle Fault/Signal Implausible
- P0220 – Throttle Position Circuit
- P1221 – Throttle Position 1 Circuit
Affected Vehicles:
- Fiat Stilo 2001-2008
- Fiat Doblo 2000-2010
- Fiat Panda 2003-2011
- Fiat Punto 1999-2010
Common failing part numbers:
IAW 5NF.T1
IAW 5NF.PS
IAW 5NF.T9
IAW 5NF.S8
IAW 5NF.S5
IAW 5NF.T2