The 2001 Rio’s 96-horsepower, 1.5-liter engine uses a mass airflow sensor to monitor the amount of air entering the engine’s intake system. As air passes through the mass airflow sensor, a heated element inside the sensor, also called a hot wire or hot film element, cools and requires additional voltage to keep it hot. This voltage increase is how the electronic control unit knows how much air enters the intake. Over time, this heated element becomes contaminated, causing a false reading. If you catch the contamination early enough, you can clean the element instead of replacing the entire MAF sensor.
Trace the air intake hose, the hose running from the air filter box to the engine, until you reach the plastic tube connecting the two halves of the hose. This tube is the mass airflow sensor.
Lift and hold the locking tab on the mass airflow sensor’s wiring harness and unplug the harness from the MAF sensor.
Loosen the hose clamps securing the air intake hose on both sides of the MAF sensor, using a flat-head screwdriver. Pull the air intake hose from both ends of the MAF sensor.
Remove the two bolts securing the MAF sensor to its bracket, using a ratchet and socket, and remove the MAF sensor.
Look inside the MAF sensor’s tube and find the small element housed inside a smaller tube; this is the hot film element.
Hold the MAF sensor over a drain pan and spray parts cleaner into the smaller tube so that it directly contacts the hot film element. Keep spraying for three to five minutes to wash away any dirt and debris from the hot film sensor. Do not touch the hot film element with your fingers or attempt to scrub it, as that can damage the element.
Set the MAF sensor back into place in the engine compartment and connect the two halves of the air intake hose to their respective ends of the sensor. Tighten the hose clamps with a flat-head screwdriver.
Align the bolt holes in the MAF sensor with those in the MAF sensor bracket and hand-thread the MAF sensor bolts. Tighten the MAF sensor bolts to between 69 and 96 inch-pounds using an inch-pound torque wrench and socket.
Plug the wiring harness into the MAF sensor’s receptacle.
Start the engine and allow it to reach operating temperature, roughly halfway up the temperature gauge.
Probe the center wire of the MAF sensor’s wiring harness with the positive lead of a voltmeter, using a piercing probe. Touch the voltmeter’s negative lead to the battery’s negative terminal.
Check the voltage reading at idle and verify that it is between 0.6 and 0.8 volts. Slowly increase the engine’s rpm and verify that the reading stays between 3.0 and 4.0 volts throughout the rpm range. If the MAF sensor fails the test, the cleaning did not repair it and you must replace the sensor.
