What Are Engine Sensors and What Happens When They Fail? - Part 1

Engine sensors play a vital role in the smooth running of your vehicle. They send important data to your car's powertrain control module (PCM) allowing it to make critical control decisions. Engine sensors work similar to the nerves in the human body sending messages to our brains. Without accurate data from these sensors, the PCM is unable to function properly thus having a negative effect on emissions, drivability and performance.

Your vehicle's on-board diagnostic system is usually able to detect when one of the sensors is failing. This will result in your dashboard's "Check Engine" light coming on. Many motorists simply ignore the "Check Engine" light and continue to drive since the vehicle keeps running. This however, is not a good idea. Since you cannot tell the reason for this light coming on, it is important to have a diagnostic done on your vehicle as soon as possible to determine the cause. The professionals at Hansma Automotive can diagnose engine problems for you, eliminating the guesswork. Contact us for an appointment today.


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There are many different types of sensors connected to your vehicle's PCM. Over the course two articles, we will discuss the function of several standout ones.

Oxygen Sensor

Your powertrain control module uses input from the oxygen sensor to constantly adjust the ratio of air to fuel to maintain an optimum fuel mixture. The sensor measures the amount of unburned oxygen in the exhaust and generates a proportional voltage signal to the PCM. The PCM then uses this information to re-balance the fuel mixture. Accurate readings from the oxygen sensor are crucial to maintaining low emissions and good fuel economy. Oxygen sensors need to be replaced more often than any other sensor. Generally, an oxygen sensor will last approximately 100,00 km (possibly more). To ensure that you are getting the best fuel economy and low emissions, you should have your sensors tested by a professional.

Coolant Sensor

The coolant sensor's job is to monitor the temperature of the coolant in the engine. The PCM uses this information to operate the engine's electric cooling fan. A faulty sensor could result in the engine overheating, where the PCM doesn't know to turn on the fan when it is needed. Incorrect temperature readings could also result in the control system remaining in an "open loop", which is a temporary state only meant to occur when the engine is cold-started. If this occurs, it could mean higher fuel consumption and increased emissions.

Throttle Position Sensor

The throttle position sensor monitors -you guessed it- the position of the throttle. This sensor is located on the throttle body. As the engine load changes, the PCM will use the information from the sensor to adjust spark timing and the fuel mixture. A worn-out throttle position sensor can cause a "flat-spot" when you try to accelerate. This sensor's effectiveness can be measured by a voltmeter. It will need to be replaced if any drops in output are recorded when the throttle is open. If you have noticed a flat spot while accelerating contact us to have this test done.

For a quick and accurate analysis of any or all of your vehicle's engine's sensors, come and speak with one of our trusted and qualified staff today. Hansma Automotive is located at 88 Shoemaker Street in Kitchener, Ontario. Let our 25 years of experience work for you.   .

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Sensors: When to Replace Them

Automotive Engine Sensors
Oxygen Sensor photo by Martin Olsson (username 'mnemo' on en/sv wikipedia and commons, martin@minimum.se)
Throttle Body photo By No machine-readable author provided. M100~commonswiki assumed (based on copyright claims). [Public domain], via Wikimedia Commons
ECM photo By User:Mgiardina09 (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Posted on May 1, 2016 .