Diagnostic trees
Follow a guided decision path from symptom to probable cause.
Engine Won't Start
The engine does not start — either it does not crank or it cranks but will not fire.
beginnerEngine Overheating
Temperature rises above normal, coolant may be lost and the warning lamp may illuminate.
intermediateBattery Keeps Discharging
The vehicle is hard to start or the battery goes flat, especially after standing.
intermediateCheck Engine Light On
The malfunction indicator lamp is illuminated, steady or flashing.
beginnerLoss of Power
The engine feels flat, especially under acceleration or on hills.
intermediateRough Idle
The engine idles unevenly, shakes or nearly stalls at rest.
intermediateABS Warning Light
The ABS or stability warning lamp is illuminated, possibly with a flashing traction light.
intermediateAir Conditioning Not Cooling
The vents blow warm or weakly cool air.
intermediateBlack Smoke from the Exhaust
Dark smoke under acceleration, often with poor economy.
intermediateWhite Smoke from the Exhaust
White or grey smoke, sometimes with a sweet smell or coolant loss.
intermediateBlue Smoke from the Exhaust
Blue smoke on start-up or under acceleration, with possible oil consumption.
intermediateAirbag / SRS Warning Light
The airbag or SRS warning lamp remains illuminated.
advancedAutomatic Gearbox Jerking
Harsh or delayed shifts, juddering or slipping.
advancedBrake Noise
Squealing, grinding or a scraping noise when braking.
beginnerSteering Wheel Vibration
The steering wheel shakes at certain speeds or when braking.
intermediateExcessive Fuel Consumption
The vehicle uses noticeably more fuel than before.
intermediateSeveral Unrelated Electrical Faults
Warning lights, dim lights and odd behaviour across several systems at once.
intermediateTransmission Slipping
Engine speed rises without a matching increase in road speed; rough or delayed shifts.
advanced