Warning Signs Your Vehicle Needs Diagnostics

Modern vehicles monitor themselves constantly. When something is not right, they often tell you, through a warning light or a change in how the vehicle drives.

The check engine light

A steady check engine light means the vehicle's computer has stored a fault. It is not always serious, but it should be checked soon. On many vehicles, even a loose fuel cap can turn the light on.

A flashing check engine light usually means a more serious problem, such as a misfire that can overheat and damage the catalytic converter. Reduce your speed, avoid heavy acceleration and have it checked as soon as possible.

Other warning lights

Lights for oil pressure, engine temperature, charging (battery) or brakes need attention. If the oil pressure or temperature warning comes on, pull over safely and turn off the engine. Your owner's manual explains what each light means on your vehicle.

Signs you can feel, hear or smell

• Rough idling, hesitation when you accelerate, or stalling
• Hard starting, or the engine cranking for longer than usual
• A noticeable drop in fuel economy
• New noises such as knocking, ticking or whining
• Unusual smells: a sweet smell can point to a coolant leak, and a burning smell can mean oil or another fluid is leaking onto hot parts
• Smoke from the exhaust that is blue, black or persistently white

What diagnostics involves

A diagnostic check usually starts with a scan tool that reads the trouble codes stored by the vehicle's computer. A code points to the system where a problem was detected, but it does not always name the exact part that has failed. That is why the codes are followed by further checks and testing to find the real cause before any parts are replaced.

This article is general information. Every vehicle is different, so check your owner's manual and have a qualified technician inspect any problem you notice.