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Hi there! I have a 12' Nissan Altima with a 2.5L engine. I've being having an issue with it for several months that is driving me crazy! The cast is showing a DTC p0101 Wich is the MAF sensor. I replaced the sensor with a generic brand and it didn't work. I replaced the sensor again with a genuine brand new OEM Nissan and the p0101 code is coming back. I check the voltage on the sensor. Readings are as follow: At Idle 1.1-1.2 volts, at 2000rpm 1.1-1.2 volts, at 4000rpm 2.4 volts. I found out this readings are within specifications and now I don't know what to think or do about this problem. Also, I want to let you know of a few other things I notice. 1. When on idle, I rev up the car to over 4000 rpm I hear a rattling nose in the engine. 2. When running, the car doesn't go over 3200rpm, If it goes over that it starts stalling and the rattling noise can be heard but it won't go over 4000rpm. All help will be really appreciated.
By the way, the car has 112000 miles, I replaced the fuel pump thinking it could be the problem. New factory recommended spark plugs as well. Checked catalytic converters, all ok.
Well, thanks for reading. Hope you guys can lead me to some others trouble shooting ideas.
 

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Hi there! I have a 12' Nissan Altima with a 2.5L engine. I've being having an issue with it for several months that is driving me crazy! The cast is showing a DTC p0101 Wich is the MAF sensor. I replaced the sensor with a generic brand and it didn't work. I replaced the sensor again with a genuine brand new OEM Nissan and the p0101 code is coming back. I check the voltage on the sensor. Readings are as follow: At Idle 1.1-1.2 volts, at 2000rpm 1.1-1.2 volts, at 4000rpm 2.4 volts. I found out this readings are within specifications and now I don't know what to think or do about this problem. Also, I want to let you know of a few other things I notice. 1. When on idle, I rev up the car to over 4000 rpm I hear a rattling nose in the engine. 2. When running, the car doesn't go over 3200rpm, If it goes over that it starts stalling and the rattling noise can be heard but it won't go over 4000rpm. All help will be really appreciated.
By the way, the car has 112000 miles, I replaced the fuel pump thinking it could be the problem. New factory recommended spark plugs as well. Checked catalytic converters, all ok.
Well, thanks for reading. Hope you guys can lead me to some others trouble shooting ideas.
Well it looks like the MAF voltage readings are correct. The reason why the engine won't go over 3200 rpm is that the system is operating in "fail safe" mode due to the P0101. The rattling noise you're hearing could be due to several causes:
  • - Loss of oil pressure causing the timing chain assembly to run loose or rod/main bearing noise.
  • - Worn out alternator bearings.
  • - Worn out belt tensioner.

Here are the most common causes of the P0101 DTC:
  • - Intake Manifold/Vacuum Leak– If there is a leak in the intake manifold, it will be impossible for the MAF sensor to get an accurate reading. Without knowing how much air is really getting into the engine. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg (inches of Mercury). At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
  • - MAF Sensor Wiring– Make sure to check around the MAF sensor for opens or shorts. Start by inspecting the wiring harness for obvious damage. If you don’t see any you can use a multimeter to test the wiring.
  • - Clogged Catalytic Converter– If you are getting P0101 accompanied by a noticeable lack in power at speed, it may very well be that you have a clogged catalytic converter. Here's how to test it:
  • At idle, the vacuum reading should be between 18 - 20 in-Hg.
  • Increase and hold speed to about 3000 RPM. The vacuum reading should drop but should go back to the previous level in a few seconds; otherwise, it's likely the exhaust system is blocked. Continue to the next step.
  • Repeat the test, but this time, snap the throttle valve open about four times, rising the engine speed to about 2500 RPM. Take note of the vacuum reading with each snap of the throttle.
  • If you see that gauge needle dropping steadily to near zero, most likely the catalytic converter or muffler is restricted.
 
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