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Author Resetting the ECU

Registered: 1st May 01
Location: Hurstbourne Tarrant
User status: Offline
22nd Jan 03 at 20:10   View User's Profile U2U Member Reply With Quote

Whilst viewing these boards you may have heard people speaking about resetting the ECU.

What is the ECU and what does it do??
The ECU is an Electronic Control Unit, what this means is that it controls everything regarding you engine on the electronic side of thinks. It controls fueling rates, air flow rates and such like.

Why and when would you need to rest the ECU
When you make modifications that effect the running of your engine, i.e. adding and Induction kit or a new performance exhaust system or backbox then you need to reset the ECU. The reason you have to do this is because your ECU is set up as standard to run with your standard equipment, when you add an induction kit for example you increase the air flow so increase fueling rates, because the ECU cannot sense what change you have made to your engine it will still try and run it as standard so when you add a performance moddification you can actually get lower performance or a 'lumpy' drive. Its a simple thing to do and as you can see from what I have told you its best to do it.

How to do it
To reset the ECU is a quite simple job to do. You will need a 10mm spanner for this, just find the negative side of your battery. If you look in the right hand side of the picture inside the red squares you will find where the negative (-) terminal is.

Undo this and take it away from the battery, you will need to leave the battery disconnected from the circuit for at least 1 hour. This means that the backup for the ECU runs flat and it looses all its data. After the hour is done reconnect the neg (-) terminal up, you may get a few sparks and your alarm beeping but nothing more, dont worry (Please note any Thatchem approved Alarms may cause problems, I am running a Toad A101CL which isn't at CAT approved alarm so I get no problems). Then start the car up, for the first 10-20 seconds DO NOT do anything, just sit and let the car idle. The car may sound lumpy and run wierd for the first few seconds but this is because the ECU has to re-calibrate to the engine settings.

When the 10-20 seconds have passed and the car sounds smooth then take it for a drive, try and do the kind of driving that you normally do in your car so that it sets up your car for that kind of driving.

Please not, for more serious moddifications to the engine you will probably need a mappable ECU or a special chip for it so the engine runs properly. But when you get to the stage of putting such serious mods onto your engine you will more than likely know what you need and will no longer need to refer to this tutuorial.

I wish you all well and many happy hours of motoring.

Submitted by Makarus

[Edited on 22-01-2003 by Adam Petherick]

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