Sensor Categories Overview
📌 The video comprehensively explains 16 different engine sensors, grouped logically into five categories for easier understanding: Position, Air Flow, Pressure, Temperature, and Air-Fuel Ratios/Emissions/Others.
⚙️ The Engine Control Unit (ECU) relies on these sensors to properly manage fuel injection and ignition timing.
⏱️ Timestamps are provided in the description for quick navigation to specific sensor information.

Position Sensors (Crankshaft & Camshaft)
📌 Crankshaft Position Sensor (CPS): Determines crankshaft position, allowing the ECU to time fuel injection and spark ignition based on piston location.
💡 CPS often uses Hall effect (3 wires) or VR (2 wires) technology, reading a ferrous trigger wheel with a missing tooth to calculate position and RPM.
📉 Complete failure of the CPS results in the engine failing to start or stalling immediately; partial failure causes rough running, misfires, or poor mileage.
⚙️ The Camshaft Position Sensor (CSPS) provides cylinder-specific data for verification and enables features like sequential injection; it reads a smaller trigger wheel.

Air Flow and Position Sensors
📌 Throttle Position Sensor (TPS): Measures the throttle plate's opening angle to inform the ECU of engine load, controlling fuel/ignition timing; modern TPS often use non-contact measurements (Hall effect, induction).
❗ Symptoms of a faulty TPS include unpredictable acceleration, incorrect idle speed (too high or low), and difficulty starting.
💨 Mass Air Flow (MAF) Sensor: Measures the actual mass of incoming air, typically using hot wire or hot film technology sensitive to resistance changes due to air temperature/flow.
📉 Failure of a MAF sensor leads to the ECU injecting incorrect fuel amounts, resulting in rough running, poor idle, and hesitation during acceleration.

Pressure and Temperature Sensors
📌 Manifold Absolute Pressure (MAP) Sensor: Measures pressure in the intake manifold using a micromachined silicon chip with a piezoelectric material to infer air mass.
💧 Oil Pressure Sensor: A vital sensor, often a piezoresistive transducer or a simple switch, usually located near the oil filter; failure can trigger limp home mode or prevent startup if oil pressure is falsely reported as low.
🌡️ Coolant Temperature Sensor (CTS): A thermistor located near the thermostat that dictates fuel requirements (cold engines need more fuel); failure causes rich running (if reporting cold when hot) or lean running (if reporting hot when cold).

Air-Fuel Ratio and Emissions Sensors
📌 Oxygen ($\text{O}_2$) Sensor: Measures oxygen in exhaust gases to determine the air-fuel ratio; upstream sensors monitor running ratio, while downstream sensors verify catalytic converter function.
⚠️ Even minor $\text{O}_2$ sensor contamination can cause rough running, but a complete failure in modern cars might prevent the engine from starting; a rich condition from failure can quickly destroy the catalytic converter.
🔥 Exhaust Gas Temperature (EGT) Sensor: A probe located directly in the exhaust stream (often near the exhaust valves) to infer air-fuel ratio or verify DPF regeneration temperature in diesel engines.
🛑 $\text{NO}_\text{x}$ Sensors: Primarily found on diesel vehicles, they verify the Selective Catalyst Reduction (SCR) system by measuring nitrogen oxides before and after the treatment process.

Engine Condition Monitoring
📌 Knock Sensor: Functions as a microphone tuned to the engine's specific knock frequency; upon detection, the ECU retards ignition timing or increases fuel to prevent damage.
🛑 Modern ECUs often trigger a limp home mode immediately upon detecting a knock sensor failure, even if the engine runs normally initially.
🌡️ Oil Temperature Sensor: Provides an added layer of protection by monitoring viscosity impact; failure can cause false warnings leading to limp mode or prevent startup if temperatures are falsely reported as too high.

Key Points & Insights
➡️ Engine sensors are categorized into five types: Position, Air Flow, Pressure, Temperature, and Emissions.
➡️ Crankshaft Position Sensor failure is critical, resulting in an immediate no-start condition.
➡️ The TPS relies on measuring the angle of the throttle plate, often using variable resistance or modern non-contact methods.
➡️ MAF/AFM/MAP sensors all aim to quantify incoming air mass, with MAF measuring directly and MAP calculating based on pressure.
➡️ If an O$_2$ sensor fails leading to a rich condition, replace it promptly to avoid premature failure of the catalytic converter.

📸 Video summarized with SummaryTube.com on Dec 11, 2025, 23:01 UTC