What are the methods for diagnosing car faults?

[Gale]

Methods for identifying car faults are as follows: 1. Rubber burning smell: When this odor occurs, first check the belts, brake pads, and tires to see if the rubber products in these areas are loose, slipping, or overheating. If it is confirmed that the smell is coming from the brakes or tires, immediately turn off the engine and stop the vehicle, waiting for it to cool down before driving again. 2. Plastic burning smell: This is mostly caused by overheating of electrical wiring. Since the plastic outer coating of wires is relatively thin, the smell is usually not very strong. However, when a short circuit occurs, it is often accompanied by localized smoke or heating, which can easily lead to combustion and fire over time. 3. Strong scorched smell: If you smell a special odor of non-metallic materials burning while driving, it is generally caused by the burning or overheating of the clutch friction plate. This smell may also be mixed with a charred odor, as clutch plates are made of composite materials including rubber and asbestos. 4. Unburned gasoline smell: If you constantly smell unburned gasoline inside the car, you should be highly alert. First, determine the location and extent of the fuel leak before continuing to drive.

[TaliaRose]

Last time my car was shaking badly, I figured out a few DIY methods from daily experience: when cold starting, squat at the rear to smell the exhaust—a strong oil smell might indicate burning oil; if the dashboard suddenly lights up with a yellow warning while driving, quickly use your phone to take a photo of the fault code; if the steering wheel vibrates abnormally, first check tire pressure and wheel balance; for strange noises under the hood, use a screwdriver as a stethoscope pressed against the engine to listen. Ordinary car owners can keep an OBD scanner plugged into the port under the steering wheel, connecting to a phone app to read fault codes and data streams, but don’t just rely on the codes—combine them with symptoms. For example, a P0171 (system too lean) might indicate a vacuum leak. Doing basic checks before repairs can save you unnecessary expenses.

[McNora]

In our workshop, fault diagnosis follows the principle of observation, listening, inquiry, and palpation: lifting the hood to check for oil leaks or cracked rubber components indicates aging; detecting a sweet smell from the exhaust during startup often suggests coolant leakage; feeling the carbon buildup thickness at the exhaust pipe outlet can indicate combustion conditions; using a stethoscope to distinguish wheel bearing noises between rustling and metallic knocking. When reading engine parameters with a diagnostic tool, pay attention to the long-term fuel trim value—anything beyond ±10% signals an issue. For older vehicles, special attention should be paid to ghost faults caused by oxidized wiring harness connectors and poor contact. Experience outweighs equipment, as 80% of electrical faults are simple issues like blown fuses.

[LeBethany]

Common diagnostics are divided into four levels of inspection: Basic level checks engine oil level and tire wear, low coolant may indicate cylinder gasket puncture; Functional level tests electrical components like headlights and wipers; Dynamic monitoring observes fluctuations in water temperature and oil pressure gauges; Professional level requires using an oscilloscope to examine ignition waveforms. Last week encountered a bizarre case: intermittent AC operation turned out to be caused by an obstructed temperature sensor behind the glove box. For DIY solutions, try disconnecting the battery negative terminal for ten minutes to reset the ECU - many electronic faults can be resolved this way.