This Impala came into the shop with a customer concern of an intermittent stall. Customer stated it had happened 2-3 times. It had happened when the customer was coming to a stop and once in a drive-thru lane.
The customer said the CEL (Check Engine Light) was on, but that it had been so for over a year.
First things first, I connected my diagnostic machine and checked for any present DTC's (Diagnostic Trouble Codes). The vehicle, as implied by the customer, had many stored codes. The one that caught my eye in reference to the current complaint was a P0102 MAF (Mass Air Flow) Circuit Signal Low.
Now time to get to the MAF sensor. When you look under the hood you will see a cover over the engine.
To remove this cover, twist the oil fill neck counter-clockwise and it will pull out.
I then removed the cover.
With the cover removed from the vehicle the MAF sensor is in plain view.
My main attention, per the DTC, was the signal wire on the MAF. I decided to check the waveform and see what it looked like. The wave form should be nice and squared. You can see from the photo below this signal was not!
It was obviously time to replace this faulty MAF sensor.
In order to remove the MAF sensor, you need a T20 Anti-Theft/Security Torx Bit socket. There are two screws holding the sensor in place. Here is a look at the sensor removed.
Now to check the waveform on the new MAF sensor. The waveform now looked normal. This verified the diagnosis and the repair.
I then cleared the codes and took the vehicle for a test drive or two. I also allowed it to sit and idle. The P0102 did not come back. I informed the customer of the need to do further repairs in relation to the other DTC's.
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