In short
A delete disables an emissions control system in software, and sometimes by removing the part: the DPF (diesel particulate filter), the EGR valve or AdBlue (SCR). In Spain it is not allowed on vehicles driven on public roads: Royal Decree 920/2017 classes a missing, modified or non-working emissions control system as a major defect, so the car fails its ITV (Spain's compulsory vehicle inspection); driving without meeting the technical requirements is a serious offence under the Traffic Act, and your insurer can reduce or refuse a payout. That is why we only do deletes on competition vehicles or vehicles not used on public roads. If yours is a road car, we diagnose the fault and fix it.
What a delete is and how it differs from a remap
A remap such as Stage 1 changes how the engine works (turbo, injection, torque) but leaves every emissions control system working. A delete does the opposite: it is not after more power, it makes the ECU stop using or monitoring a particular system. It usually has two parts:
- Software: the ECU stops managing the system and stops logging faults related to it.
- Physical, in some cases: the part is removed or emptied (the filter, the catalytic converter) or a passage is blanked off (the EGR).
The first can be undone if the original was saved. The second cannot, short of fitting new parts. Many people come to us asking for a delete when what they really have is a fault that can be repaired, and that difference is what saves the most money.
The systems usually deleted and why they fail
| System | What it does | Why it tends to play up | What to check first |
|---|---|---|---|
| AdBlue / SCR | Injects urea into the exhaust to reduce nitrogen oxides | Crystallisation, tank pump or heater, NOx sensor | Fluid quality, sensors and pump |
| DPF | Traps soot from the exhaust and burns it off in regenerations | Short trips that do not allow it to regenerate, differential pressure sensor | Accumulated ash, sensor, regeneration history |
| EGR | Sends part of the exhaust gas back into the intake | Carbon build-up that blocks it or leaves it open | Cleaning, actuator and air mass meter |
| GPF / OPF | Particulate filter on petrol engines | The same as the DPF, on petrol | Same as the DPF |
| Lambda sensor / catalytic converter (O2) | Measures oxygen in the exhaust and monitors the catalytic converter | Ageing sensor, degraded catalytic converter | Sensor readings before and after the catalytic converter |
| SAP (secondary air) | Injects air into the exhaust when cold so the catalytic converter warms up sooner | Seized pump or valve | Pump, valve and pipes |
| EVAP | Collects vapours from the fuel tank | Leaks, purge valve | Leak test |
| Swirl flaps / TVA | Intake flaps and throttle | Spindle wear, carbon build-up | Actuators and play |
| MAF (air mass meter) | Measures the air entering the engine | Dirt or ageing of the sensor | Live values versus expected values |
There are other functions people also ask to have "deleted" that are not emissions control systems, although they have their own nuances:
- Start&Stop: most cars let you switch it off with a button every time you start. Disabling it permanently means changing the factory configuration.
- Immobiliser (Immo): it is an anti-theft protection. Disabling it makes sense in motorsport or with an unprogrammed replacement ECU, but on a road car it leaves the vehicle more exposed and your insurer may require it. The right solution is almost always to clone the ECU or sort out the no-start problem.
- DTC (fault codes): hiding a code does not fix the cause. It only makes sense when the component no longer exists on a competition vehicle.
Before deleting: the fault can almost always be fixed
We are a workshop (Ronda de la Pescadería, 24, bajo, 28801 Alcalá de Henares (Madrid)), so the first thing we suggest is finding out why the system is failing. Electronic diagnostics show whether the problem is the component, a sensor giving a false reading, the wiring, or a usage pattern that does not let the system do its job (for example, a DPF on a car that only does short trips). With that we give you a quote for the repair, and you decide with all the facts.
If your car has already been deleted somewhere else and you want to pass the ITV with peace of mind, what you need is the opposite: get the original software back and, if it is missing, refit the component.
When a delete does make sense
- Competition vehicles used on circuits or at events that are not driven on public roads.
- Vehicles and machines that only work inside closed premises or private land, without going onto public roads.
In those cases we work just as we do on a remap: a saved copy of the original software, a modification developed for that specific ECU and a check afterwards. The most requested ones have their own page: AdBlue, DPF and EGR.
AdBlue
Start countdown, NOx sensor, pump or crystallisation: what fails and how it is fixed.
DPF
Why the diesel particulate filter clogs, how it regenerates and what to do before you even think about deleting it.
EGR
Jerking, smoke or limp mode: how to tell whether it is the EGR and how it gets fixed.
What we need to assess it
- Make, model, engine and year of the vehicle.
- What the symptom is: warning light on, limp mode, AdBlue message, constant regenerations…
- Whether anything has been done to it before (cleaning, parts replaced, modified software).
- What the vehicle is used for: road, motorsport or closed premises.
Tell us the symptom and the vehicle. We will tell you what might be going on and what options you have, starting with the ones that let you pass the ITV.
Official sources
- Royal Decree 920/2017 regulating vehicle inspection (ITV), Annex I, sections 8.2.1.1 and 8.2.2.1 (BOE, Spain's official gazette)
- Royal Legislative Decree 6/2015, Spain's Traffic, Motor Vehicle and Road Safety Act, arts. 12.7, 76.o) and 80.1 (BOE, Spain's official gazette)
- Act 50/1980 on Insurance Contracts, arts. 10 to 12 (BOE, Spain's official gazette)
- Royal Decree 866/2010 on vehicle modifications (BOE, Spain's official gazette)
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