ECU Remapping – What You Have to Know

Here are things you should have before mapping/remapping a car.


  1. Math

you need to have a reasonable understanding of maths, and how to use a scientific calculator as you get more involved. By the end of this guide you will know what 14x(1-2.373 to the power of 0.263)/ A squared x (B + 460) means, now don’t worry I will break this down into each part of the equation later on and it is not as complicated as you may think, that said it would help if you knew why there are parts of the equation inside ( )and what “to the power of” means


  1. car condition & components

To design a map you need to understand what condition a car is in, who is driving it and for what purpose and what its mechanical problems are. A 20,000 mile car will be able to be mapped further than a 80,000 mile car, assuming they have had identical daily use, as the internal condition of the engine will be better. A car with auto transmission will want a different map from a manual one. A family man will want a different map to tow his caravan than a sales Rep in an identical car. Does this car have known gearbox issues? Increasing the torque low down will cause potential failure sooner. There are many more things to consider, these will be covered in “designing your map”

What components make up the car, not just things like how many cylinders and its total cc but you need to know is it mechanical injection, common rail, variable fuel pressure, direct injection, does it have mechanical or electrical turbo bypass, does it have EGR or DPF even down to air-conditioning, are the sensors on it voltage variable or pulse variable?


  1. maps inside ECUs

What maps are actually inside the ECU, there can be 6 or many hundreds, you need to know

what map is actually the “limiting map” for example when there are 6 maps in a basic system one of those maps will be the limiting map, it usually the “torque map” but not always it may be the “fuel temperature map”. So you need to know what maps you actually have and which ones limit the others before you can actually tune it correctly.


  1. Chemistry

yes you need to be a chemist to be a high quality tuner, you will be dealing with the effect of altitude on air quality, the effect of temperature on air density, the burning of fuels and the amount of gases produced, the effect of compressing gasses and how temperature’s build up from both compression and expansion. What gasses can be used to aid “gains” and what causes “losses”, how we can use these things to improve our tuned map.


  1. computer knowledge

Use a computer, not just the basics you really need to know how to use:

In Excel you need to be able to write formulas for multiplication and division of cells, you need to be able to map cells, format numbers and set borders, text and cell colours and of course Copy and

Paste functions. Why? Well you’re going to start by doing maths on non-existent maps to understand the changes and calculations required to make those changes, then you’re going to link one map to another map and see how changes in one affect another map.

Notepad++, this is not Notepad this is a different version that will allow you to open and convert files into different file extensions.


  1. HexEditor

Hex Editor, you will need to know what “HEX” is so you can start to understand what language is inside the ECU this will help you when you have a problem, its not something you will need until much later on in this guide and by the time I introduce it you will have the basic knowledge to use it


  1. Tuning software

Tuning software, from the easy to use ECM titanium to the harder WinOls. Easy to use does not mean it’s what you should use. Whilst ECM is designed to be an easy to use program it really shouldn’t be used beyond the training level. I will explain later why I say this.


WinRar and or 7-zip, because you’ll be sending files via the internet.

Email, and additionally a file transfer program such as “We transfer” because your zip’d file will be too big to send via email or you’re anti-virus will block the zip’d file as it may contain a virus!!! Well that’s how viruses are transmitted by email attachments so they do not look at the file just see a zip’d file and go “oh no it’s bad” and block it.


  1. ECU reading program, combined with an ECU reading tool.

You need to connect your computer to the ECU, often via the 16 pin OBD port, however a lot of ECU’s need to be removed from the vehicle and taken apart, inside there is a programming port which is just a line of gold pads about 1mm in diameter that you need to connect to. So you’re going to need 2 tools, one for a OBD connection the other for a direct to ECU connection, then you’ll need the software to operate each tool and you need to know how to use this software and save the file you have read from the ECU so you can work on it.


  1. good bench and comfortable chair

You need a good wooden toped bench, preferably with a light coloured top so you can find all the screws you have removed and as it may be necessary to remove a chip from the board to be able to read the main chip you’ll need to find

this afterwards. A comfy chair, it’s important to be sat at the correct height for you bench and you’ll be there for a few hours so if it’s not the right chair you’ll get neck and back pain, maybe so much so you decide to “that’ll do I’ve had enough for today” rather than “yep that’s finished”


  1. magnifying glass

Well you need a magnifying glass so you can look on the ECU and read which is pin 1 and a good light source, I use a telescopic magnifier with a built in tube light, its mounted on the end of the bench and I can pull it in front of me or push it out of the way in a second so as not to have to look for it and drop what I’m holding.

Oh and its worth buying a tool called a “third hand” it’s usually a metal base with a few random clips on it, this allows you to hold something still whilst holding solder in one hand and a soldering iron in the other.


  1. supply of 1k and 10k resistors

Then you want a supply of 1k and 10k resistors, a handful of capacitors personally I have quad buffers, canbus transmitters and more, there is a full list in the Equipment Appendix at the end of this guide, but its about £25 for all these items and you have them so that IF you need them you don’t to stop what you’re doing and drive into town.


  1. tools for soldering and scratching

You’ll need a good selection of tools, ECU’s are normally well hidden requiring removal of many parts to get to them before you can remove them.

Then you’ll need a proper soldering workstation that is temperature controlled with both a hot air blower and a solid tip soldering iron. You will also need a “flux pen” this needs to be “ROSIN” flux to aid any soldering you do, then you’ll need a cleaner to remove old flux and old solder.

A sharp knife to scratch away any coverings, then you need a few different shaped tweezers and thin nosed pliers so you don’t burn your fingers…

So now do you see that the £200 clone Kess V2 at wasn’t such a cheap way into this job!


  1. ecu remapping abilities

Apart from removal of the ECU (where needed when an OBD read is not possible) you will also need to be able to carry out mechanical checks before you start to even think to re map this ECU. Sensors need to be checked, cleaned or renewed, oil changed, airfilter replaced, airfilter housing modified, inlet manifold cleaned, EGR flap blanked, DPF filter removal, crankcase filter replaced and modified the list goes on and these things need to be done before any map changes are made, you can never map a car because it has a problem. Too often I see that a map has been done with a DPF delete because the car had a DPF problem. All this will do is mask the fault codes, the ECU will still be dealing with the fault and your map will not be doing its job because the ECU will have a map that over rides the actual output signals.

Additionally you will need a battery stabiliser and a bench power source.


  1. bench power source

Your bench power source will be required to power up an ECU removed from a car to allow you access to the programming pads, you need 12 or 24 volts dependant on what it has normally and I recommend a 2amp supply, in reality you need about 0.5 to 0.75 amps to power an ECU however if you use a 1amp supply it may just cause you to “brick” the ECU ( the term “brick” refers to the fact that it is now only useful as a brick to stop the car rolling down the hill) this is because a 1 amp rated supply will have an efficiency rating on an cheap power supply around 10%THD that means it’ll give between 0.9 and 1.1 amps in its normal operating temperature range, but hang on your in your garage and it’s been 3 degree’s overnight and now its 10 am, the power unit will be out of range and may only give 0.6 amps, then your ECU is cold so it now needs more power so instead of 0.75amps it needs 20% more so that’s 0.9 amps and you have just shut down your ECU, if that’s mid read, or worse mid write it’s a brick. So why 2amps and not 5amps? Well you have an open ECU and your connecting wires to it, drop a wire with 5amps and it turns into a portable welder sparks fly and ECU is brick, at 2amps which is really 1.6amps it should survive any short circuit you do.


  1. battery stabiliser

Right then what’s a battery stabiliser? Well as your sat there car door open, ignition on the battery is losing volts, as it can take 30mins to read or write an ECU that’s a lot of volts its losing drop to low and bosh ECU brick, why not use a battery charger? Well these give current, and current will damage your computer interface, never use jump leads onto another car or battery if the lead slips it’ll spike the system, battery booster…no these are designed for a short sharp boost not a constant slow drain. If you have no choice a 2amp battery charger is the last result, often sold in local stores such as Argos or Halfords as “battery maintainers” these will not produce enough current to damage things, but they are not to be trusted as they will not maintain a level they will just trickle away a bit of power so as things turn on and off (you will need to turn ignition on and off several times) the voltage will be up and down, this will cause an error at the least it will give you a “wake up error” which is a no read situation.


  1. “crib” sheets

I have a set series of things to do during the entire process.

My first crib sheet includes driving the car to make sure it hasn’t got a fault, checking all the lights work, check the remote door locks work, the heated seat and more.

Mechanical condition deal with checking all the mechanical things are ok, perform a check of the sensors, you will need a generic scanner for this to read out the ECY fault codes. You must check that all the sensors on the engine are working correctly, test with the engine off, with the engine just on idle and then with it held at 3500rpm for 30 seconds.


Self-preservation sheet,

has the customer got the radio code because you will disconnect the battery, check under the seats for mobile phones or other valuables, never remove anything ask the customer to remove it. Look in the boot check what is there and make a list of items. Check the tyres, look for anything like a nail in the tread that may actually be a slow puncture, make sure the tyres are legal and check the tyre pressures, this will tell you how well he looks after the car and also if there is a slow puncture. I also check brake pads, oil level and condition, air filter etc. If anything is not correct do not proceed with the map. Fix the car first or you will have problems after the map which you will have to search for and fix before you get paid, if you did not know the condition before you started you will spend a lot of time trying to understand and undo what you’ve done.

I record all these on my crib sheets either by a tick to say I’ve checked or by writing in a number or a note, then I get the customer to sign it before I start work on his cars maps. We will also keep sheets for the changes we make, we will have one that looks at each component of the system to see who

it’s made by, what’s its part number, what does it do? It’s working range so we can refer quickly to the information and make job easier.



Btw, it’s not original. thanks for who have made contribution on the web.