How To Reset Your E.c.u.

[VALKYRIE YB70]

I wrote this article a few years ago in an attempt to dispel the myth that it is not possible to alter the engine control unit`s factory settings.

In fact the simple procedure outlined below should be performed after every performance mod. (such as fitting a cold air intake) & can even be of benefit if you`ve spent the whole week stuck in commuter traffic jams & want to restore your cars performance for the weekend!.

Resetting Your ECU (Engine Control Unit)
Hyundai cars are designed to be driven in all areas of the world, by people of all ages and levels of experience and sophistication. They are set to operate at all altitudes and temperatures and to use fuels of varying octane-rating and purity.
Unsurprisingly, the electronic engine control unit of your vehicle has been pre-set to a `one-size-fits-all` state of tune. Whilst the ECU has the capacity to adapt to the owners driving-style to a certain degree, the base-settings are extremely conservative and Hyundai's are famously set to run rich!

Most owners would naturally suppose that this situation is something over which they have no control, this is not the case.
This document will instruct any owner on how to change the ECU settings of their car, without the alterations being detectable by the Dealership, the Insurance Company, or indeed having any effect on the vehicle's warranty.
The operations described are recommended as a first step after taking over ownership of the car, after carrying out any performance modifications, or after any temporary change in the way the vehicle has been used ( i.e. city-bound use, towing etc.).

Firstly bring the car to normal operating temperature by driving for 15 minutes or so.
Now open the bonnet and disconnect the earth lead from the battery, ensure this is not touching any part of the bodywork - insulate if necessary - and wait 5 minutes.
Next depress the foot brake for 20 seconds - this will completely discharge the ECU's capacitors via the brake lights.
The next step (to be carried out immediately, while the engine is still warmed-up) is to carefully re-connect the battery earth lead, close the bonnet and now drive the car in a spirited fashion (accelerating rapidly through the gears, full-throttle straights etc. etc.) for a full 30 minutes. Try to choose a quiet time on the roads for this, (i.e. early on a Sunday morning!).

This period of driving will `re-educate` your ECU into adopting more aggressive timing curves and alter the fuelling to match. It will also allow the unit to recognise any modifications you have made and to react accordingly.
If, on the other hand, you are not interested in outright performance, but are more concerned with economy and flexibility, use your normal driving style during this 30-minute run!.

Over time, the ECU will slowly revert to the factory settings......especially if it is not being driven `spiritedly` on a regular basis.
Accordingly, many owners tend to do this reset monthly, or before a track day or even a long run.

Cheers,
Nick.

[Scoupy]

thanks for the info, can this be doen on all hyundais including the series 1 scoupe? Do u know anything about the computer when changing the engines cam to a larger more powerful one. I was wondering if it were possible to do this without having to replace the computer or buying a piggy back
Thanks

[sleeperxl]

Wow thats some top info will that work on say a 98excel (accent)

[kpx]

what is a bonnet and earth lead?

[Dutch_Turbo_GT]

Bonnet: engine hood
Earth lead: the wire from the ( - ) connection from the battery to somewhere on the bodywork or the chassis. This represents the - (minus) in the DC powercircuit. The + (plus) is switched in most cars (except Subaru I believe...).

[moc]

hi,
just a question, if negative lead disconnected how do break lights work???
and as asked before is this done while engine running??
regards
mick

[Dutch_Turbo_GT]

Do you actually believe the breaklights will work when you disconnect the negative lead?? The breaklight is to decharge the power in the system because the brakelights DO work when the key is NOT in. There's no switch in between...

You have to reset while the engine is NOT running, you can try it but it's not very smart... Just shut down the engine and do as VALKYRIE told before, this is the right way.

[Ravenheart]

Only want to point that I think that the 'E' of ECU doesn't means "engine" but "electronic".

[Dutch_Turbo_GT]

Hey,

you're right, but it doesn't add any value to this topic...

[Ravenheart]

Certainly it does not, so I hope this one does:

Wouldn't it be easier to remove the ECU fuse instead of disconnecting the battery?
I guess then the capacitors won't discharge but I don't know much of electricity and only the logic level of electronics.
so, if I'm right and the capacitors won't discharge, any ideas to discharge them?
if I'm wrong, what about the first question?