Information guide
Read common engine and emissions fault-code explanations. A code is not a definitive diagnosis: vehicle-specific checks are needed before a solution is chosen. This guide does not offer cleaning, sensor replacement or mechanical repair, and does not recommend deletion for road-going vehicles.
4.9/5500+ Google ReviewsSee Google ReviewsThe diesel particulate filter is no longer trapping soot effectively. Common on high-mileage diesels and cars used mostly for short trips. Diagnosis confirms whether the filter is blocked, damaged or whether sensors are at fault before any solution is discussed.
DPF specialist service scope and restrictionsThe filter has collected more soot than regeneration can clear. Frequent on vehicles that never complete a regeneration cycle. A forced regeneration may help if caught early; heavy accumulation needs further assessment.
DPF specialist service scope and restrictionsThe pressure across the filter is lower than expected, which can indicate a damaged or emptied filter, or a pressure sensor or pipe fault. Proper diagnosis distinguishes between the two before any work is quoted.
DPF specialist service scope and restrictionsThe exhaust gas recirculation valve is not flowing enough, usually due to carbon build-up. Symptoms include rough idle, hesitation and increased emissions. Cleaning or software solutions depend on the vehicle and the diagnosis.
EGR specialist service scope and restrictionsAn electrical fault in the EGR valve circuit: wiring, connector or the valve motor itself. Diagnostics will confirm whether the valve has failed electrically or mechanically.
EGR specialist service scope and restrictionsThe SCR system is not reducing NOx as expected. Causes range from AdBlue quality and injector faults to NOx sensor drift or catalyst ageing. Left unresolved it triggers countdown warnings and eventually a no-start condition.
AdBlue / NOx enquiry informationThe AdBlue dosing system is not performing within tolerance, often a pump, injector or pressure fault. Typically accompanied by a mileage countdown on the dashboard.
AdBlue / NOx enquiry informationThe system believes the AdBlue quality is poor. Sometimes genuinely contaminated fluid, sometimes a failing quality or level sensor. Diagnosis identifies which before money is spent on parts.
AdBlue / NOx enquiry informationAn electrical fault in the upstream NOx sensor circuit. Sensor failure is common and often misdiagnosed as a catalyst problem, so testing comes first.
AdBlue / NOx enquiry informationThe downstream NOx sensor readings are implausible, pointing to sensor drift or failure. One of the most frequent causes of persistent AdBlue warnings.
AdBlue / NOx enquiry informationThe turbo is not producing expected boost: boost leaks, sticking vanes, actuator faults or a failing turbo. Must be diagnosed and resolved before any remap, as tuning an underboosting engine masks the fault and risks damage.
Turbo / Boost enquiry informationBoost pressure exceeds the expected level, often a sticking actuator or control fault. On tuned vehicles it can also indicate a calibration issue, which is why we only calibrate within safe tolerances.
Turbo / Boost enquiry informationSwirl flaps or intake runners are stuck, commonly from carbon build-up or failed actuators. Affects low-end response and economy. Options depend on the engine and are confirmed after inspection.
Intake enquiry informationThe position sensor reports implausible flap positions, usually wear in the flap mechanism or sensor. Common on several VAG and Mercedes engines.
Intake enquiry informationThe upstream lambda sensor circuit has an electrical fault. Affects fuel mixture control and emissions. Sensor testing confirms whether the sensor or wiring is at fault.
Lambda / O2 enquiry informationThe catalytic converter is not cleaning exhaust gases as expected. Causes include catalyst ageing, misfires or sensor faults. Diagnosis identifies the real cause before any solution is discussed.
Emissions enquiry information