Engine light P0101

Which model 9-5 do you have aero arc or linear?Also which engine do you have?

Heres the long verion.
P0101 OBD-II Trouble Code
Technical Description

Mass Air Flow (MAF) Circuit Range/Performance Problem
What does that mean?

Basically this means that there is a problem with the Mass Air Flow (MAF) sensor or circuit. The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4.0 seconds. Other MAF sensor circuit DTC trouble codes are P0100, P0102, P0103, and P0104.
Symptoms

You will likely not notice any serious drivability problems, although there may be symptoms.
Possible Solutions

The simplest thing to do is to reset the code and see if it comes back. Then start with the cheapest, easiest repair procedures:

* Inspect for the following conditions:
An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:
- The secondary ignition wires or coils
- Any solenoids
- Any relays
- Any motors
* A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.
* A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 230 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
* The barometric pressure (BARO) that is used in order to calculate the predicted MAF value is initially based on the MAP sensor at key ON.
* When the engine is running the MAP sensor value is continually updated near WOT. A skewed MAP sensor will cause the calculated MAF value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
* A high resistance on the ground circuit of the MAP sensor can cause this DTC to set.
* Any loss of vacuum to the MAP sensor can cause this DTC to set.

If you suspect the condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

As for the location of the sensor, it is located behind the right headlight if I read correctly.

Try what I had originally posted first clear the light and see if it comes back. If not then problem solved. If it reappears then we go from there. Also run a quick look over your intake system from the air filter box back look for loose broken pieces or any place air can penetrate the system besides coming through the filter.

Also look for a vacuum leak you could also try cleaning the ass air flow sensor with some mass air flow sensor cleaner. To see if that makes any difference.

That code is related to the Mass Air Flow sensor. If you have a live scanner, start the vehicle and read the live data from the MAF and let me know what you find. My guess is the sensor is bad.