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How To: Reset the ECU

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  • [All Models] How To: Reset the ECU

    This is another extremely common question.
    "How do I re-set the ECU and why do I need to?"

    The reason why is due to any number of factors. Commonly the introduction of a dirty great new air filter or induction kit will upset the ECU's fuelling as the MAS (mass airflow sensor) will be reading a far greater volume than it will inside a stock airbox.
    Also the fitting of a FSE powerboost valve may well give the same erratic symptoms as the fuel is now being pressured into the injector rail at a higher rate than before.
    There is also the occasion when nothing seemingly makes sense and its just running either too rich or too lean.

    So before you go straight for an expensive diagnostic check up or start replacing expensive sensors, re-setting the ECU is the easiest things to do and it costs nothing.

    You'll need to disconnect the battery, ideally overnight (as a residual charge can sometimes mean 30 mins isn't enough). For those with alarms, you might have to just lock it manually with the key and "wing it" for the night or borrow a wheel lock if your nervous.

    In the morning, re-connect the battery and turn the car over. Let it idle for a good 5 mins and be happy that its found base idle satisfactorily (can sometimes take as long as 20 minutes), then take the car out for a 5 mile run using the gears to a decent range / revving freely. This will allow the ECU to recalibrate and hopefully take onboard what the sensors are reading and balance out the fuelling.

    So there you have it. It's costless and it's a doddle. You should always look at this simple method before spending ludicrous amounts on sensors that are actually ok.
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