Codes P0102 and P0101?

DERRILL1958

MEMBER
2011 NISSAN ALTIMA
2.5L
4 CYL
2WD
AUTOMATIC
160,000 MILES

Check engine light is not showing on dash only comes up when I plug in scanner. Replaced the mass air flow w/ OEM, new air filter, changed out O2 sensor (again OEM) in Bank 1 and have replace upper air intake tube which did have a crack in it. I also have looked for cracked hoses/ vacuum leaks. I don't know what else to do. Car is starting fine but when pressing the gas pedal while driving I can feel a slight hesitation/surge. Sometimes when I'm at a red light its idle is so low I feel as though it may shut off but never has yet. I don't know what else to do or check for. Lost my husband 7 years ago who was our mechanic and funds are limited, so a ginormous repair bill is not in my budget. I do plan on tuning it up soon but I'm not sure if that would help at all. Thank you in advance for any answers or guidance with this car.

3 Replies

AL514

MECHANIC
4,632 POSTS

Hello, do you know if this vehicle falls under California emissions standards? It should say on the tag under the hood. There is a difference in wiring diagrams for some vehicles depending on if they are California emissions. These codes p0101 and p0102 are both circuit codes. And with the low power you're mentioning it sounds like the MAF is under reporting the fuel amount. This might have something to do with the actual 12v supply to the sensor. I'll put the wiring diagrams up to check for battery voltage at the sensor. Also, what kind of scan tool do you have, can you read live data? If so checking to see what the sensor is reading will help. It should be grams per second (g/s). Do you have a basic multimeter to do some voltage checks? I will keep posting more information here for you.
There are quite a few Technical Service Bulletins on the p0101 code and an engine computer reprogramming update. They mention if there are no other drivability concerns though, which you seem to have.
It is odd the check engine light doesn't show up until you plug in your scan tool, unless system voltage is already low, I would also check with a multimeter across the Battery with the vehicle idling and see what the voltage reading is. Low system voltage can cause all kinds of issues. Do you notice any of the lights flickering at night while driving?

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf

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Thursday, October 6th, 2022 AT 4:14 PM

DERRILL1958

MEMBER
2 POSTS

Car is under both California and US emissions and thank you I had no clue about this. My scan tool is only an OBD scan tool. The code only comes up in scan tool but no service light ever on dash. At first, the service engine light did come on that is how I knew problem existed but after changing O2 sensor and MAF the light no longer appeared but was definitely stored in OBD. I tried erasing and driving and all that, but it's still there. I have no flickering lights while driving at night. I've also checked fuses too just in case. I replaced the battery last winter and the voltage is over 12v. Thank you for the diagrams somehow, I think it may have something to do with the MAF plug. I don't hear a click when I connect but I don't see any wires, which may be an issue. I'm wondering if the ECM does in fact need to be reprogrammed but I would have to take to Nissan dealer and I'm a little leery about them. I have a 2005 Nissan Sentra and all lights, dash brake etc, kept blowing out two blocks into driving. They charged an arm and leg to fix but the car kept coming bk doing the same thing. Out of desperation I worked on the car myself and found a minuscule nick in back light tail bulb took months to solve so my faith is a little shaky with them. I wouldn't worry so much about this one going out of commission, but winter is approaching, and my daughter is borrowing my spare Nissan so if this is not resolved I may be stranded. Thanks for your help I will check voltage and pray a lot so I don't drift off to the side of the road one day.

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Friday, October 7th, 2022 AT 10:26 AM

AL514

MECHANIC
4,632 POSTS

What exactly is your charging voltage at the battery and then at the battery negative post and the Alternator positive post? As for the connector on the MAF sensor it should lock in place, so the connector is not loose. Take a look inside the connector and see if there is any corrosion, and check pin 2 for battery voltage. The charging system voltage should be above 12, really it should be 13.7 to 14.3 area. If it's not that's a problem. The vehicle has a lot of miles on it, so I wouldn't be surprised if you start to find corroded connections. Especially if you live in an area where they use a lot of salt on the roads. I live down south, so we don't see as many vehicles with crusty salted up connectors as up north.
Another thing to check if the MAF has 12v on pin 2 is the purge valve. If the purge valve is stuck open it can skew the MAF reading, with the car running, if you unplug the purge valve and pull off the hose coming from the canister there should be no vacuum being pulled through the valve, (meaning it's not stuck open). In the diagram below is the Purge valve circled in green. Unplug the electrical connector and pull off the section of hose in purple. And check that side of the valve for any air being pulled in. There shouldn't be any. Do this with the car running, you won't hurt anything, it might set a code, but just clear it after. You're only testing right now. If it's okay, we need to take a look at the signal the sensor is sending out. Your obd2 scan tool probably has a live data option. Most do at least for engine data. It should tell you what g/s the MAF is reading at idle.
So do those few checks, along with a number of the charging system voltage. And make sure that connector does click onto the sensor tight. Let us know what you find and if you have any more questions.
I don't blame you for not wanting to go to the dealership.

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