Blocked or aged SCR catalyst
Catalyst efficiency drops with mileage, contamination, or short-trip driving.
SCR System Repair & Diagnostics
The catalyst is only half the SCR system — we fix all of it.
The Selective Catalytic Reduction (SCR) system is what turns harmful NOx into harmless nitrogen and water. When any part of it fails — catalyst, sensors, pipework, temperature probes — the entire emissions system loses confidence and the warnings begin.
Symptoms we fix
- AdBlue / SCR warning light
- Reduced power / limp mode
- Failed MOT emissions test
- Excessive AdBlue consumption
- Visible exhaust leaks before or after the SCR can
Common causes
Temperature sensor failure
T-sensors before/after the SCR feed the control strategy — failure stops dosing.
Pipework leaks
Exhaust leaks upstream of NOx sensors throw all downstream readings off.
Crystallised injector
AdBlue not delivered correctly = SCR cannot work, even if the catalyst is healthy.
Our diagnostic & repair process
- Step 1
Full SCR diagnostic
Live NOx in/out, temperature data, dosing pressure and quantity all read in real time.
- Step 2
Targeted repair
We replace only the failed element — catalyst, sensor, pipework or injector.
- Step 3
Adaptation reset
Many SCR repairs need a fresh adaptation/learn cycle to clear long-term fuel and dosing trims.
Why choose Fastlane
- Specialist SCR knowledge
- Fleet-friendly scheduling
- Honest part-vs-replace decisions
Vehicles covered
Cars, vans and light commercials across all major brands.
If your SCR system is throwing warnings, get it looked at by specialists — not generalists.
Google Reviews
5 / 5
Based on 297+ Google reviews for our sister business Fast Lane Performance — the same team behind Fastlane AdBlue Solutions.
Read all reviews on Google →SCR Repair vs AdBlue Delete — which makes financial sense?
Repairing an SCR system means replacing whatever has actually failed — the catalyst, a temperature sensor, pipework, or the dosing components. On some vehicles a full SCR rebuild can run up towards £5,000, while smaller sensor or pipework jobs start from around £300. The downside is that a repair puts the original system back in place, so further SCR or AdBlue faults can appear later as the vehicle ages.
Our AdBlue delete is a fixed £300–£400 one-off, permanently removes the SCR/AdBlue fault, does not impact your MOT, and carries our lifetime warranty so the fault cannot return. Where an SCR repair quote is high — or the vehicle has a history of repeat faults — a permanent delete is very often the more economical route.
We'll give you a straight comparison for your vehicle so you can decide. See our AdBlue delete service →
Frequently asked questions
In some cases, mild contamination responds to professional cleaning. Heavily blocked or damaged catalysts need replacement — we will tell you honestly which yours needs after a proper diagnostic.
Related help
Quick links to popular services, brands, fault codes and coverage areas.