K&N has millions of satisfied customers, yet we do occasionally get instances where a dealership or service provider has blamed our product for a vehicle problem. We attempt to resolve these misunderstandings by speaking directly to the service technicians.  In any event, we take care of the consumer through our Consumer Protection Pledge.  In issues regarding MAF sensors, we have been able to recover many of the allegedly “bad” sensors and test them to diagnose the actual cause of the failure.  In most of these cases the "bad" sensor was actually functioning properly and was misdiagnosed by the dealership or service provider.  The diagram below is a summary of our findings.

In addition to out of range sensors, functioning and failed sensors have also been sent to an independent forensic laboratory for analysis.  A few of these sensors were found to have trace amounts of oil on the thermistor.  The amount of oil was so minimal that an accurate analysis of the oil's source could not be determined.  The trace amount of oil can conceivably be found from two possible sources: fuel in the combustion chamber or motor oil used as an engine lubricant that gets suspended in crankcase vapor.  Our experience in the lab is that trace amounts of oil don't change the sensitivity of the sensor enough to cause an "out of range" electronic signal.  Furthermore our testing has shown that K&N air filter oil will not come off a K&N air filter even in extreme conditions.  More on this topic here.

As of the date of our last test shown below, K&N air filter oil cannot be confirmed as the source of contamination on a sensor nor can any oil type be attributed to a sensor’s failure.
 

MORE DETAILS ON SILICONE & TESTING Mass Air Flow Sensor Electronic Testing at K&N: The MAF sensor is placed on a test bench designed and built by K&N Engineering.  The test bench can flow air through the sensor at variable flow rates, ranging from idle to full throttle.  The flow of a sensor is then compared to a new sensor.
	MAF Sensor Test Bench

Example of Sensor reading Normal		Example of Sensor reading Out of Range
Example of Failed Sensor (flat line)

Microscopic Examination:

Example of Clean Thermistor		Example of a Contaminated Thermistor

A MAF sensor is located under the hood of your vehicle and is subject to a heat, cold, vibration, etc., in other words, a hostile environment.  An engine performing as expected can contribute to contaminating a MAF sensor. The presence of gas fumes, a vehicle backfiring, combustion blow-by and even water condensation can contribute to contamination of a sensor. Ironically, the presence of contamination does not necessarily conclude the sensor is not functioning properly and requires replacement.

Independent Forensic Analysis:
An elemental and chemical analysis of the contamination has more often than not shown to be silicone.  K&N filter oil does not contain silicone.  The silicone can actually be traced to the sensor’s housing of the electronic circuitry. The silicone can seep out of the housing area onto the sensor.
 

		MAF sensor thermistor probes connect to the circuit board.  Silicone covers the circuit electronics and it can seep down contaminating the thermistor.  This photo shows the silicone compound referenced, covering/protecting the electronics. The probes leading to the thermistor are connected to the underside of this circuit board.
		This photo shows a probe demonstrating the stickiness of the silicone material.
		This photo shows a sensor with silicone covering the electronics.  Note the small gold processor in center.
		This photo is a close up of the processor under the silicone.
		This photo is an extreme magnification of the processor. As can be seen, this is a complex sensor with thousands of connections and components all of which must be intact for the sensor to function properly.

Below is a more detailed summary of our actual test results.

Electrical Failure:  Electrical issue within sensor compared to a new sensor's specifications
Manufacturing Defect: A layer of the membrane sensor peels back causing electrical failure - known as de-lamination
Sensor Never Failed:  Service provider error; sensor was not malfunctioning
Severe Silicone Leak:  The silicone leak was too severe to run on the test stand

* Well over 50% of the "damaged" sensors sent to us were functioning properly meaning they were never damaged in the first place and cannot be attributed to any vehicle problem.  Click here for more information on how this may happen.

Below is the list of MAF sensors that were sent to K&N for testing.  The list includes dealerships that misdiagnosed the problem and blamed a K&N product for the failure.  Test results are also shown.