Diagnostic Help
What is your vehicle actually doing?
You don't need to know which component has failed. Start with the symptom you can actually see, hear or feel, then work towards the cause logically.
Start with the symptom
Don't diagnose the car before you've diagnosed the car.
A lack of power doesn't automatically mean a turbo fault. A DPF warning doesn't automatically mean the DPF needs replacing. And a sensor fault code doesn't automatically mean the sensor is faulty. Start with what the vehicle is doing and gather evidence from there.
Choose a symptom
Which best describes the problem?
Pick the closest match. You don't have to get it exactly right — this is just the starting point for narrowing the problem down.
Lack of power / poor performance
→Feels sluggish, won't pull properly, struggles under load or has suddenly lost performance.
Start guided diagnosis →
Won't start
Coming soonThe engine turns over but won't start, or nothing happens when you try to start the vehicle.
Difficult starting
Coming soonTakes too long to start, needs several attempts or is worse when hot or cold.
Cuts out / stalls
Coming soonThe engine stops unexpectedly while driving, when slowing down or while idling.
Poor or uneven running
Coming soonRough idle, misfiring, hesitation, surging or an engine that simply doesn't feel right.
Warning light on
Coming soonAn engine, emissions, DPF or other warning light has appeared and you want to understand why.
Smoke from the exhaust
Coming soonUnusual black, blue or white smoke from the exhaust during starting, acceleration or normal driving.
Unusual noise
Coming soonWhistling, knocking, rattling, hissing or another noise that wasn't there before.
High fuel consumption
Coming soonThe vehicle is using noticeably more fuel than normal and there isn't an obvious explanation.
Something else / not sure
Coming soonYou know something isn't right, but you're not sure which symptom or system best describes it.
Already have a fault code?
If you've scanned the vehicle and already have a diagnostic trouble code, you can search the Speed Tweaks fault-code library directly.
Search fault codes →