DTC P0100 Mass Air Flow Sensor

This Diagnostic Trouble Code (DTC) relates to a Mass Air Flow (MAF) sensor that is not providing the expected readings for the operating conditions as observed by the Powertrain Control Module (PCM). This stored Diagnostic Trouble Code (DTC P0100) is not definitive enough to just replace the part based upon its’ indication.

The Mass Air Flow (MAF) measures the amount of air entering the engine in Grams Per Second.

How it accomplishes this task is thru the use of heated wires placed in the airflow. A simple 3 wire sensor explained; The Mass Air Flow (MAF) has a switched battery power feed (key on) and a chassis ground circuit for the heater. The third wire is a signal wire that connects to the Powertrain Control Module (PCM). (fig #1)

As the air passes over the heated wires in the sensor they require more current flow (amperage) to maintain the heat within them. This signal is sent to the Powertrain Control Module (PCM) and it monitors the frequency on the signal wire to determine if the MAF is stuck low or high (vdc).

If the sensor is less than 1.11 grams per second or greater than the maximum allowed based upon expected readings for at least 1/10 of a second the PCM will turn on the Malfunction Indicator Lamp (MIL).

There are condition that must also be met such as battery above 11 volts, engine speed above 500 rpm, and no blocking codes.

To perform the job correctly you should look at the items that could have caused the reported failure of the sensor. This would include an inspection of the basic items, such as air filter, loose or broken air duct tubing, vacuum leaks, malfunctioning Positive Crankcase Ventilation (PCV) system, lack of maintenance, etc.

You should check for Technical Service Bulletins (TSB) including those that address the possible need to reprogram the Powertrain Control Module (PCM) that may relate to the Diagnostic Trouble Code (DTC P0100). If it needs reprogrammed that can be performed with J2534 tools such as ours.

After you are satisfied that no problems exist from the basic inspection, you should use a Scan Tool*, such as our 2x80 series scan tool with a good software package and  a good Digital Multimeter (DMM) such as UEI’s ADM 4200 can be used to confirm the Mass Air Flow (MAF) sensor readings are out of range.

As you can see many things can cause a DTC P0100 like a loose connection, a bad ground, an air filter that doesn’t fit properly and allows dirty air to enter, and the sensor is only one of the possibilities.

Let’s address the idea of cleaning a sensor that is dirty. As a mechanic you will have to weigh the cost benefit ratio to determine if cleaning is warranted. If you are going to replace the sensor it will only take a few minutes (usually while waiting on the part) to try and clean it. First you should use the proper cleaner like CRC’s sensor cleaner and not brake parts cleaner. Our results of cleaning are mixed, sometimes it works sometimes it does not. Our best results are from warming the sensors heater up and using clean compressed air (not shop air) to blow off the heater. Then allow it to cool and use CRC’s product and thoroughly wash the heater. Allow it to dry, reinstall it and retest.

Fundamentals training book

Performance Diagnostics book