# Back to stock (original) software

> Back to stock: restoring the original ECU software to sell the car, pass the ITV, visit the dealer or undo someone else's modification.

- URL: https://www.reprogramacionesmbv.com/en/back-to-stock-software/
- Index for AI (llms.txt): https://www.reprogramacionesmbv.com/en/llms.txt
- Versión en español: https://www.reprogramacionesmbv.com/software-original/
- Reviewed: 2026-10-15

---

Undoing a remap is easy if someone saved the original and a good deal trickier if not. It also matters whether only the software was touched or parts were removed. Here are the three scenarios and what can be done in each.

**In short:** Going back to stock software means writing to the ECU (engine control unit) the factory program it had before a remap or a delete. If the original was saved, as we always do on our jobs, it's a straightforward write. If the car has been modified elsewhere and there's no copy, the ECU's hardware and software version have to be identified and an original that matches exactly has to be recovered. What software can't bring back are parts that were removed: an emptied particulate filter or a blanked-off EGR valve has to be refitted. Price on request; in Alcalá de Henares or wherever the car is, in the Community of Madrid (the Madrid region).

## When does it make sense to go back to standard?

- **You're going to sell the car** and don't want the buyer to inherit something they didn't ask for, or you want to sell it with the paperwork and the software matching.
- **Your ITV (Spain's compulsory periodic vehicle inspection, similar to the UK MOT) is coming up** and the car has a delete or a modification that hasn't been legalised as a vehicle modification (reforma). We explain it in [legality, ITV and insurance](https://www.reprogramacionesmbv.com/en/legality-itv-insurance/).
- **You're taking it to the dealer** for a service, a recall or a fault, and you'd rather they found the factory software.
- **You've bought a car that had already been modified** and you don't know what was done to it or how.
- **You're not happy with the modification**: the car runs worse, uses more fuel or has behaved oddly since it was done.
- **You're a used-car dealer** and want to deliver your cars in standard form: we explain it in [used-car dealers](https://www.reprogramacionesmbv.com/en/trade/car-dealers/).

## Scenario 1: we did the remap

On all our remaps we read the ECU and copy the complete original file before writing anything. If you want to go back:

1. **We find your original** by vehicle and ECU.
2. **We check it's the same ECU**: if it was replaced because of a fault, the original read back then may not work as it is.
3. **We write the original** using the same method it was read with.
4. **We clear the fault codes and check** that the car works as standard and that no warnings remain.

If another garage remapped your car and kept your original, ask them for it: with that file the job is just as straightforward.

## Scenario 2: the car was modified elsewhere

Here there's no copy of the original, or the one there is can't be trusted. Writing "any old original" for that model is a mistake: the same engine can have different ECUs and software versions depending on the year, the gearbox and the updates the manufacturer applied. The job goes like this:

1. **Read the complete ECU** and note its hardware and software number.
2. **Identify what was modified**: it isn't always just the power map. Sometimes functions have been disabled, fault codes hidden or changes made to the gearbox control unit or other modules.
3. **Recover an original that matches** that hardware and software version exactly, or a compatible later factory version.
4. **Write it and check the other control units**: if something was also changed in the [automatic gearbox](https://www.reprogramacionesmbv.com/en/automatic-gearbox-tuning/) or another module, that has to be undone too.
5. **Check on the road** that the systems that had been disabled are working again.

In most cases it can be done. When it isn't possible because of that ECU's protection or because no compatible original can be found, we'll tell you and look at other options.

## What software can't bring back

This is the part that causes the most surprises. Many deletes have a physical side, and writing the original software **doesn't undo it**:

| If this was done… | When it goes back to standard… | What needs doing |
|---|---|---|
| Particulate filter emptied or removed | The ECU expects a filter and doesn't find one | Fit a new filter or one in good condition |
| EGR blanked off with a plate | The ECU detects there's no exhaust gas flow | Remove the plate and check the valve |
| Catalytic converter emptied | The sensors detect that it isn't working | Fit a new catalytic converter |
| Sensors disconnected or removed | Fault for missing sensor | Refit and reconnect them |
| AdBlue system unused for months | Pump, injector or fluid may be damaged | Check and repair the system |

That's why, before writing the original, we check which parts are fitted. If any are missing, we give you a quote for what needs replacing, so you know the total cost before we start. If what the car has is a delete, it's worth reading [deletes](https://www.reprogramacionesmbv.com/en/deletes/) too.

## Before writing: what we check

**Checks before going back to standard**

- ECU: That it's the one the car came with or, if it was replaced, what immobiliser data it holds
- Software version: That the original we're going to write matches that hardware exactly
- Other control units: Whether the gearbox control unit or other modules were also modified
- Physical parts: DPF (diesel particulate filter), EGR, catalytic converter and sensors fitted and in place
- Stable voltage: Battery in good condition and external power supply during the write

The last point isn't a minor detail: a write that's interrupted halfway by a voltage drop can leave the ECU unable to start the car. That's why we keep the car powered throughout the process.

### If you're going to sell the car

Going back to standard before the sale avoids the buyer discovering the modification on their first visit to the dealer or at the ITV. And if the car had a vehicle modification (reforma) legalised because of a remap, remember that the vehicle's technical data sheet (ficha técnica) will keep showing it until the reverse is processed: check with your ITV station first.

## Price

It's **price on request**. It depends above all on which scenario you're in: writing an original we read ourselves is nothing like identifying and recovering one with no copy. How the ECU is accessed and whether parts need replacing also play a part. We give you a fixed price after reading the ECU.

Tell us what car it is and what you know about what was done to it. If you know nothing, that's fine too: we'll find out by reading the ECU.

## Frequently asked questions

### How do I know if my car has been remapped?

Sometimes the car itself tells you: more pull than its version should have, a warning light that doesn't come on when it should, or a particulate filter that never regenerates. The reliable way is to read the ECU and compare its software with the factory software for that version. We do this as part of [electronic diagnostics](https://www.reprogramacionesmbv.com/en/vehicle-diagnostics/).

### Does a software update at the dealer wipe the remap?

If the dealer writes a new factory software version to the engine ECU, yes, it replaces whatever was there. But there isn't always an update available for that engine, and it doesn't refit removed parts. Also, when they plug in their equipment they may see that the software wasn't the factory one.

### I had a Stage done with you – how long does it take to go back to standard?

It's usually the simplest case, because we start from the read of the original we made before remapping: it has to be written and the car checked. How long it takes depends on whether that ECU is written via the diagnostic port or has to be removed; we'll tell you when we book you in.

### Can I keep both files and switch whenever I like?

Every switch means writing the ECU, and that's not something to do lightly. If what you want is to go back to standard temporarily (for a service, for example), tell us and we'll work out the most practical option.

### Does it work for a car I bought with the AdBlue deleted?

If the system is still fitted, writing the original software is usually enough to get it working again, sometimes with some repair to the system itself, which hadn't been working for a while. If parts were removed, they have to be replaced. We assess it by reading the ECU.