TEST 3: Testing The MAF Signal
OK, now for the test you signed up for! Testing the mass air flow sensor's output signal. Read the test steps carefully and familiarize yourself with them, before doing the test.
To perform this test and obtain a correct result, the Quest's engine must be at normal operating temperature. So, you'll need to start up the Mini-Van and let the engine warm up.
A good MAF sensor will produce a MAF voltage signal value that will increase when you accelerate the engine and decrease when you decelerate the engine.
If the MAF sensor is defective, the MAF voltage signal value will stay stuck in one value when you accelerate/decelerate the engine.
IMPORTANT: This test must be done with the MAP sensor connected to its connector.
OK, this is what you'll do:
Place your multimeter in Volts DC mode.
Probe the MAF sensor wire that is identified with the letter C in the photo with the red multimeter test lead.
Ground the black lead at the battery (-) negative terminal.
Crank and start the already warmed up engine.
Note the Volts DC reading on your multimeter as the engine idles. At idle and with a fully warmed up engine, you should see about 1.2 Volts DC on your multimeter.
This reading may fluctuate a bit, but no matter what the instability in the reading, this will be your base voltage reading.
Manually accelerate the engine. The voltage reading on your multimeter should increase.
At around 2500 RPM's you should see about 2.4 Volts DC on the multimeter.
Let the engine return to idle. The voltage value on the multimeter should return to the base voltage value you recorded in step 5.
This voltage reading may not be the exact same but should be very close.
Repeat this as often as you need to verify that the voltage value increases/decreases when you accelerate/decelerate the engine.
Let's take a look at what your test results mean:
CASE 1: If the voltage reading increased and decreased smoothly and in a linear fashion as you accelerated and then decelerated the engine, then the Quest's MAF sensor is working correctly.
CASE 2: If the voltage reading DID NOT increase and decrease smoothly as you accelerated and then decelerated the engine, then the mass air flow sensor on your Nissan Quest is bad. Replace the MAF sensor.
If this info really saved the day, buy me a beer!