96 GM Astro has code P0101 and low fuel mileage

Symptoms:

This minivan set a code P0101 (Mass air flow A circuit range/performance) after driving in the highway for over 65 mph. The code was reset but returned after a week. During this time, the gas mileage also dropped.

Basic Concept:

This code deals primarily with the mass sensor and can be tested normally with a scanner like "All in One" scanner recommended in this blog. With engine running and scanner hooked up, the sensor readings can be monitored and analyzed for faults.

Repair Strategy:

Before buying the scanner, the map sensor and top of the engine can be viewed by removing the doghouse (see picture) to have a visual condition of the wirings and vacuum hoses to the map sensor.

Note:

To locate the wiring colors of the map sensor and location, please contact ATS if you are a member.