Accepted Answer

Sorry for the info request, the model and engine size was not listed when I had looked at your question. The trouble codes p0131 and p0151 are in regards to a lean situation that is being picked up by the oxgen sensors. These codes are not important as the P101 can cause for them. So the P0101 trouble code is the most important at this time. The P0101 trouble code is in regards to a mass air flow sensor issue. Here is how this code is caused.

The mass air flow (MAF) sensor is an airflow meter that measures the amount of air that enters the engine. The powertrain control module (PCM) provides the correct fuel delivery for a number of engine speeds and of engine loads using the MAF sensor signal. A small quantity of air that enters the engine indicates deceleration or idle. A large quantity of air that enters the engine indicates an acceleration or a high load condition. The MAF sensor has the following circuits:

•	An ignition 1 voltage circuit

•	A ground circuit

•	A signal circuit

The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency that is based on inlet air flow through the sensor bore. The frequency varies within a range of around 2,000 Hertz at idle to about 10,000 Hertz at maximum engine load. The PCM uses the following sensor inputs in order to calculate a predicted MAF value:

•	The manifold absolute pressure (MAP) sensor

•	The intake air temperature (IAT) sensor

•	The engine coolant temperature (ECT) sensor

•	The engine speed

The PCM compares the actual frequency signal from the MAF sensor to the predicted MAF value. This will determine if the signal is stuck because of a lack of variation, or is too low or too high for the operating condition. DTC P0101 sets if the actual frequency signal from the MAF sensor is not within a predetermined range of the calculated MAF value.

There is some serious testing that goes into diagnosing this one. Honestly you will need a scan tool to monitor certain parameters to verify what the ecm is reading from the map sensor and the mass air flow sensor for starters. If you are using a K&N air filter, this can be cause by over oiling the filter causing a build up of oil on the mass air flow electronics. There is a mass air flow sensor cleaner made by CRC that most auto part stores sell. If you have access to a class 2 scan tool, I can get you more info on the actual testing. Feel free to contact me with any questions! Good Luck!

Expert:	Carhelp4u
Pos. Feedback:	99.8 %
Accepts:
Answered:	8/10/2008

ASE CERTIFIED TECH

ASE CERTIFICATION