More Sensor Details

 

Oxygen (O2) Sensor: Measures the amount of unburned oxygen in the exhaust so the electronic control module (ECM) can determine if the air/fuel mixture is too rich or too lean. It may become less responsive with age or when contaminated by coolant, sulfur or motor oil. Failure can produce a rough idle and poor fuel economy. O2 sensors usually have replacement intervals of 30,000 to 50,000 miles on older vehicles, and 60,000 to 100,000 miles on newer vehicles.

Coolant Temperature Sensor (CTS): Reports the temperature of the engine coolant so the ECM will know when the engine has warmed up. This sensor may degrade with age. Failure can result in excessive fuel consumption and high levels of carbon monoxide emissions.

Knock Sensor: Detects engine vibrations that can indicate a "knock" or premature detonation of the air/fuel mixture in the cylinders. The ECM can then adjust the timing to eliminate the knock. Sensor failure can cause engine damage if the knocking persists.

Vehicle Speed Sensor (VSS): Monitors vehicle speed so the ECM can regulate shifting and torque converter lockup. Sensor failure can cause erratic shifting and also disable cruise control.

Manifold Absolute Pressure (MAP) Sensor: Measures the load on the engine by reading the amount of vacuum pressure in the intake manifold. The ECM can then adjust ignition timing to compensate for increased load. MAP sensors may drift out of calibration, which can trigger the MIL light and cause the engine to hesitate and run poorly. Various conditions such as a plugged or loose vacuum hose also can cause erratic MAP readings.

Mass Airflow (MAF) Sensor: On some fuel-injected vehicles, this sensor measures the speed and density of the air entering the engine. If the sensing element becomes contaminated, it can cause stalling, hesitation and hard starting. It eliminates the need for a MAP sensor.

Manifold Air Temperature (MAT) Sensor: Measures temperature of the incoming air so the ECM can adjust fuel mixture according to air density. Failure can result in the engine running too "rich" or too "lean."

Throttle Position (TPS) Sensor: Tells the ECM the engine is at idle, at wide-open throttle or somewhere in between. The computer can then adjust fuel mixture and ignition timing accordingly. If theTPS fails, the engine should still run, but is likely to experience surging and misfiring.

Crankshaft Position (CPS) Sensor: Tells the ECM which cylinder is going to fire next and also reports engine speed. Failure of this sensor will normally cause the engine to shut down because the ECM cannot function without this data and it will not activate the fuel pump.

If all of this seems confusing, no need to worry. This is precisely why you bring your car, light or medium truck to Quality Care Auto, where highly trained and fully certified technicians with access to state-of-the-art diagnostic equipment and computer-based technical reference data are ready to meet your needs.

If you have additional questions about preventive maintenance, diagnostic systems, sensors or anything related to the safe and economic operation of your passenger car or light/medium truck, visit our Ask the Expert page.

 

 

 

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