One of the easiest repairs you can make to your own vehicle, is to replace a part known as the mass airflow sensor, typically located near the air filter box under the hood. The first indication you have a problem with the sensor is usually because the engine throws a code that lights up your Service Engine Soon light. Other indications are hesitation on acceleration and generally idle rough.
Last December, my car started hesitating every time I started off, and the harder I pressed down on the gas, then more it would sputter. However, once I got up to speed, it would even out.
Soon after those symptoms started though, my Service Engine Soon light came on and the hesitations and sputters seemed to get worse. Rather than taking it into a shop for a diagnostic test, I took it to AutoZone and they read the code free of charge. Once you have the exact code, you can diagnose what the problem is and possibly handle the issue yourself.
I should point out that I am referring specifically to a 2000 Nissan Maxima, but this information applies to a number of vehicles, particularly the type of codes that are read from your SES light. The OBDII codes are universal for all American, European and Asian cars.
I quick search online and I found a list of the codes and what each one refers to and quickly diagnosed the problem. This code indicates a problem with the fuel management system on the right cylinder bank. The right bank is also called the rear bank which contains cylinders 1,3,5.
It turns out it was Code P0171 - Fuel Injection System Too Lean (Bank 1).
The code explanation explained that the Front Heated Oxygen Sensor for the right bank sent signals to the Engine Control Module indicating an excessively lean fuel mixture. The ECM attempted to correct this problem by directing the fuel injectors to supply more gasoline. Further signals from the Oxygen Sensor indicated that the attempt to correct the lean mixture condition was unsuccessful, and the fuel mixture continued to be too lean.
Then it listed possible causes: Intake air leaks, Defective Front Heated Oxygen Sensor, Fuel injectors, Exhaust gas leaks, Incorrect fuel pressure, Lack of fuel, Faulty Mass Air Flow Sensor
Instead of taking it in for servicing, I went online to look for what I needed to do to change this myself. No matter what kind of car you drive, you can find some kind of forum for it which will contain a lot of useful information. From this Nissan online forum, I determined that the most likely caused cause was either an oxygen sensor (this car has 3), or something called a Mass Airflow Sensor (MAF).
As I researched further, I determined it was more than likely the MAF Sensor since it seemed to be an issue after a certain number of miles with this particular model ofcar. I looked online and ordered a new MAF from Amazon. I got the part for $90 and it arrived about a week later. Keep in mind I was reading on various forums about people taking their cars to dealers and having the same thing replaced for $500 and $600, so it was well-worth the cost for the part.
Replacing a Mass Air Flow Sensor in Nissan
I took up the challenge myself and it was very simple. I would say that even someone with very little automotive experience could do it. If you can change your oil, you can do this.
Here is the entire process in detail:
- Disconnect the negative battery terminal.
- Open the air filter box, then disconnect the MAF sensor. The wiring harness that goes to the MAF is also attached to something else (a blue plug on my car). I disconnected that as well so I could move the whole harness out of the way.
- I couldn't get to all the bolts attaching the MAF tube to the airbox so I had to remove the box. This was fairly easy except for a couple exceptions. One of the bolts is in a tight spot and I had to use a 6 inch extension for my ratchet.
- After unbolting the airbox you need to loosen the clamp on the other side of the MAF tube.
- Once eveything is free remove the airbox. Some wiggling and pulling was required but it came free in the end.
- After you get the airbox out you can easily remove the MAF tube using the same 10mm socket wrench you used to unbolt the airbox.
- It is recommended that you replace the air filter too.
- With the new MAF tube bolted back onto the airbox, connect the airbox and MAF tube back up.
- Bolt in the airbox, making sure the intake is aligned properly. There's an odd shaped plastic tube that runs from the front of the hood, down over the radiator. This is the air intake and it needs to connect to the airbox. It's loosely done and you probably had to jiggle it loose when removing the box.
- Reconnect the negative battery cable.
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If you crank your car and the Service Engine Soon light still displays, but there are no signs of a problem, disconnect the negative battery cable and leave it overnight. The codes will reset. You should have no other issues.
You do need a couple of special tools like a 6-inch socket extension, and a magnetic stick comes in handy to grab one of the bolts once you loosen it. I also changed the air filter inside the abox. In all, it took about 20 minutes, and that included washing the air filter box in the sink. Since this repair, I have not had any other issues.