Poor mpg?
Rough idle?
Failed emissions?
Mobile Lambda and O2 sensor diagnostics and repair, at your driveway or depot across South & West Wales — finding the sensor at fault before it costs you fuel, emissions or an MOT.
What Lambda sensors do, and why they fail
Lambda (oxygen) sensors measure how much unburnt oxygen is left in the exhaust and feed that data back to the ECU, which uses it to fine-tune the fuel mixture in real time. Most cars have at least two — one before the catalytic converter, one after.
Sensors degrade with age and mileage, and can be damaged by oil leaks, coolant contamination, or a failing heater circuit inside the sensor itself. Once a sensor reads incorrectly, the ECU starts making the wrong fuelling decisions.
We connect to the ECU, compare live sensor readings against expected values, and confirm exactly which sensor is at fault before recommending any repair.
Not every sensor fault means the same thing
Slow / Lazy Response
A sensor that's aged and slowed down reacts too late to changes in the exhaust, causing inefficient fuelling.
Oil, Coolant & Silicone Damage
Leaks or the wrong sealants can coat the sensor tip, giving false readings or killing it outright.
Heater Circuit Faults
Most sensors have an internal heater to reach operating temperature quickly — a failed heater triggers a fault even if the sensor itself is otherwise fine.
Wiring & Connector Faults
Chafed wiring, corroded connectors or heat damage near the exhaust can mimic a failed sensor.
Upstream vs Downstream Faults
A pre-cat and post-cat sensor fault point to very different problems — we identify exactly which one and why.
Failed Emissions / MOT
A faulty sensor often shows up first as a failed emissions check, before the warning light even appears.
Four steps to a properly running engine
Book Your Slot
Tell us the warning light or symptoms and we'll get a visit booked in quickly.
We Come To You
Home, work or depot — anywhere across South & West Wales, no towing to a garage.
Diagnose & Repair
Live sensor data reviewed against expected values, the faulty sensor identified, and repaired on-site.
Test & Confirm
Live data re-checked and fuel trims confirmed back to normal before we leave.
Book a DiagnosticOther faults sorted in the same visit
Full Fault Diagnosis
A complete system scan if you're not sure what's actually wrong yet.
EGR Solutions
Sticking or faulty EGR valves diagnosed and resolved at the source.
DPF Solutions
Blocked filters and failed regenerations diagnosed and resolved.
Economy Tuning
Once fuelling is reading correctly again, ask us about getting even more from every tank.
The right sensor, not just any sensor.
Cars often have several oxygen sensors, and replacing the wrong one wastes money without fixing anything. We confirm exactly which sensor is at fault using live data before any parts are touched.
Genuinely Mobile
We bring the full diagnostic and repair kit to your driveway or depot — no towing or waiting for a garage slot.
All Major Manufacturers
From everyday petrols to high-mileage diesels, we work on Lambda and O2 systems across the vast majority of makes and models.
MOT-Safe, Compliant Repairs
Every repair restores proper fuelling and emissions control — nothing that risks an MOT failure.
Straight-Talking Diagnosis
A clear explanation of what's actually wrong before any work starts, with no pressure to over-spend.
From drivers chasing a fuel economy or emissions issue
"Fuel economy had been dropping for months. Turned out to be a lazy downstream sensor — fixed on the drive."
"Failed the emissions part of my MOT. WCH found the faulty sensor and had it sorted before the retest deadline."
"Previous garage wanted to replace both sensors on a guess. WCH confirmed it was just the one — saved me money."
Mobile across South & West Wales
If you're within reach of these areas, we'll come to you. Based further afield? Get in touch — we regularly travel beyond our core patch for the right job.
