The Implications of Dirty Car Sensors

Car sensors can get dirty with normal use. Symptoms of dirty sensors include reduced engine power, worse gas mileage, or an engine that hesitates.

On average, there are more than 30 individual sensors installed in modern vehicles on the road today. They range in sizes smaller than a quarter to the size of a rolled up dollar bill. Car sensors are typically used to collect data from various systems and relay it to the ECU. However, if the sensor is dirty, it's effectiveness can be compromised significantly.

If something’s malfunctioning on your vehicle and you have a mechanic inspect the issue, they may look at the sensor that has an impact on the problem. Checking to make sure the sensor isn’t dirty is one of the least expensive repair options but is the most common. By recognizing the symptoms of dirty sensors you can be better prepared to resolve these issues.

Oxygen sensor

Cars today have at least one oxygen sensor, and may have as many as four or five depending on the model. These sensors are prone to becoming dirty because they are located around the exhaust. Their job is to monitor how much unburned fuel is present in the exhaust system. When they are dirty, they may provide inaccurate information or none at all, which prevents the system from making changes in the air-fuel mixture to reduce the amount that is unburned. This will reduce the car's performance and the engine will have to work harder.

Manifold absolute pressure sensor

The MAP (manifold absolute pressure) sensor changes the voltage and frequency of the intake vacuum, depending on the air pressure in the manifold. When the sensor is dirty, it doesn't make the necessary changes, which slows down or speeds up the ignition timing. As a result, the car hesitates when you try to accelerate or go up an incline and has poor overall performance, even though it will continue to run.

Mass airflow sensor

The MAF or mass airflow sensor measures the volume and density of airflow to tell the engine how much fuel must be added. When the sensor gets dust or dirt on it, incorrect information can be sent to the diagnostic computer. The wrong amount of fuel is added, which can lead to stalling, sputtering, and hesitation as well as loss of power or lower fuel efficiency.

Wheel speed sensor

The ABS sensor or wheel speed sensor helps you maintain control of your vehicle when you need to brake or when you are driving on slick pavement. If this sensor gets dirty, it can cause the ABS light to turn on, indicating a problem when none actually exists.

In general, sensors that work with the engine impact the performance when they get dirty. The engine may sound rough, not run as well, or have less efficiency or power. For instance, the oil pressure sensor tells you when the amount of oil is getting low. If it’s dirty, it may not respond and you could run out of oil and damage your engine.

Keeping your sensors clean is important to ensure optimal performance and a long life for your vehicle. If you ever have an issue with your car you think is related to a dirty sensor, contact a professional mobile technician from AutoFactorNG.

Symptoms of a Bad or Failing Transmission Speed Sensor

Common signs include harsh or improper shifting, cruise control not working, and the Check Engine Light coming on.

The transmission speed sensors are used to calculate the actual gear ratio of the transmission while in use. There are generally two speed sensors that work in conjunction to provide accurate transmission data to the vehicle’s powertrain control module. The first is known as the input shaft speed (ISS) sensor. As described, this sensor is used to monitor the speed of the transmission' input shaft. The other sensor is the output shaft speed (OSS) sensor. If either of these two sensors falls out of alignment or experiences electrical issues, it impacts the operation of the entire transmission.

After registering data, the two transmission speed sensors, also commonly referred to as a vehicle speed sensors (VSS), send data to the powertrain control module (PCM), which compares these two inputs and calculates which gear the transmission should engage for efficient driving. The actual gear ratio is then compared to the desired gear ratio. If the desired gear and the actual gear do not match, then the PCM will set a diagnostic trouble code (DTC) and illuminate the Check Engine Light.

Should either or both of these speed sensors fail, you may notice one or more of the following issues:

1. Harsh or improper shifting

Without a valid speed signal from these sensors, the PCM will not be able to correctly control the shifting of gears within the transmission. This may cause the transmission to shift roughly or more quickly than normal. It's also common that a problem with these sensors can impact the shift timing, extending the interval between transmission shifts. An automatic transmission is hydraulically controlled and designed to shift smoothly.

When the transmission shifts hard, it can damage internal components including valve bodies, hydraulic lines, and in some cases mechanical gears. If you notice that your transmission is shifting harshly or roughly, you should contact a local ASE certified mechanic as soon as possible.

2. Cruise control does not work

Since the transmission speed sensors monitor the input and output shaft speed, it also plays a part in monitoring the cruise control. When the sensors fail to deliver accurate data to the onboard computer on your car, truck, or SUV, the powertrain control module (PCM) will send an error code to the vehicle’s ECU. As a safety precaution, the ECU will shut down the cruise control and render it inactive. If you notice that your cruise control does not engage when you press the button, contact a mechanic so they can inspect the vehicle and determine why the cruise control is not working. It may be due to faulty transmission speed sensors.

3. Check Engine Light comes on

If the signals are lost from the transmission speed sensors, the PCM will set a DTC and illuminate the Check Engine Light on the vehicle dashboard. It also can indicate that there is an increase in tailpipe emissions is occurring that surpasses acceptable limits for environmental contaminants from motor vehicles.

In any case, if you notice that the Check Engine Light comes on, you should contact a local mechanic to scan the error codes and determine why the Check Engine Light is illuminated. Once the problem has been fixed, the mechanic will reset the error codes.

If the problem rests with the speed sensors, depending on your particular transmission, the professional ASE certified mechanics from AutoFactorNG may be able to replace the sensor. Some speed sensors are internal to the transmission and will require the transmission to be removed from the vehicle before the sensors can be replaced.