So you’ve installed a shiny, new mass air flow sensor. And you’ve landed on this page because you’ve searched “what to do after replacing mass air flow sensor.”
The answer is quite simple: You do Nothing.
Seriously. You don’t have to do a damn thing. Go on with your day. Close this window, stop screwing around, and get back to work.
Let me guess…. You heard that you need to reset your car’s computer after replacing a mass air flow sensor by disconnecting the battery for 15 minutes.
Or maybe you heard that you need to let your car idle for 30 minutes to let the on-board computer recalibrate?
I call bullshit on both of these actions. The vast majority of cars are going to automatically recalibrate themselves after the new mass air flow sensor is installed.
Is either of these actions going to hurt your car?
No. They won’t.
So if you want to do one of these things after replacing your mass air flow sensor, be my guest. But before you do either, take a quick read through this article and hear me out as to why I think each is a waste of your time.
Disconnecting the battery after replacing the mass air flow sensor
The most common thing I hear people saying needs to be done after replacing your mass air flow sensor is to disconnect your car battery for 15 minutes. There are a couple reasons why I personally wouldn’t do this.
Disconnecting your car battery resets EVERYTHING
Not too long ago, I tried a stupid hack on my 1999 Volvo V70 to shut off the check engine light. The hack involved disconnecting the battery for 30 minutes to reset my Volvo’s on-board computer. It was a bad idea.
As I should have known, the hack didn’t work. The good news is this: it didn’t cause any problems in the car. The bad news is this: it caused a bunch of inconveniences.
First, there was a security feature on the factory stereo that requires a four-digit code be entered whenever the battery is disconnected. I had just bought the car and had no idea what the code was. So I had to search through all the documentation I got with the car to find the stupid code. It was hand-written on a business card and was stuffed into a crusty pocket in the Volvo owner’s manual.
Second, I had to reprogram the clock and all my stereo presets. Yeah, I know… First world problems. But nonetheless, it’s an inconvenience.
And finally, the biggest pain in the ass of all…. I took the car for an emissions test the following week and it failed!
It failed because I reset the car’s on-board computer. The guy who performed the emission test told me that resetting my Volvo’s computer cleared out data on some of the sensors that provide data for the emissions test and therefore the car couldn’t properly communicate with the testing system.
Ugh. So he told me to drive the car for about 50 miles at a constant speed of about 60 mph and bring it back to be re-tested. I took it back a few weeks later and my Volvo passed the emissions test.
This sucked. I’m busy, you’re busy…. We’re all so friggin busy these days, who the hell wants to go back and do another emissions test? Not me! It was a stupid inconvenience that I wouldn’t have had to go through it if I didn’t reset the Volvo’s computer.
Let’s move on to the other useless “what to do after replacing mass air flow sensor” thing…
Idling for 30 minutes after replacing the mass air flow sensor
This is just plain stupid. You’ll waste gas.
According to the good people at AAA, your car will burn ¼ to ½ a gallon of gas for every hour it idles.
Thirty minutes of idling won’t waste a ton of gas… but at today’s prices, why bother?
Here’s what you need to know… most car computers will automatically recalibrate after a couple days of normal driving. Do this instead of letting your car idle in your driveway for half an hour. At least you’ll be burning gas to get someplace you need to go and not wasting it in your driveway.
What to do after replacing mass air flow sensor?
At the end of the day, what you need to do after replacing your mass air flow sensor is just drive normally.
It might take a couple of days for your car’s on-board computer to recalibrate. So if your check engine light stays on or you still experience some other issues like black smoke coming from your exhaust, give it a few days and you’ll probably be good to go.
If things don’t improve, maybe it wasn’t your mass air flow sensor that was bad. If your check engine light stays on after several days, do another ODB scan or bring your car to your mechanic and have it looked at.