CarFix · Guides
Engine diagnostics: warning lights, DPF, EGR, sensors
What a steady vs flashing lamp means, and which bay to book before limp mode.
Check-engine light: what to do before you drive on
A steady lamp is a diagnostic event. A flashing lamp is a stop-driving event. The difference protects the catalytic converter.
DiagnosticsDPF cleaning and diesel particulate filter warning light: what to do
A DPF warning light after short urban trips is common. Learn regeneration, forced clean, and when to book diagnostics.
DiagnosticsEGR valve cleaning symptoms: rough idle and limp mode on diesel
A clogged EGR valve causes rough idle, smoke, and limp mode. Cleaning or replacement often follows a proper OBD diagnosis.
DiagnosticsTurbocharger failure symptoms on diesel and petrol engines
Loss of power, blue/grey smoke, and whistle or siren noises are classic turbo fault signs. Book diagnostics before the catalytic converter suffers.
DiagnosticsAdBlue problems and SCR warning light: crystals, range, and no-start risks
AdBlue crystallisation and quality issues trigger SCR warnings and eventual no-start countdowns on modern diesels.
DiagnosticsOxygen sensor failure: check-engine light and sudden fuel economy drop
A lazy O2 / lambda sensor triggers mixture codes and thirsty running. Diagnose before replacing catalytic converters.
FAQ
Can I drive with the check-engine light on?
Steady: carefully to a workshop. Flashing: reduce load and book diagnostics immediately.
Will clearing the code fix the car?
No. The fault returns until the cause is repaired.