2011 Altima. Got a code P0101 which is the MAF sensor. I replaced it with a Genuine MAF sensor and cleared the code. But once in a while my SES light comes on and it is the same Code P0101. Is this code stored in the ECM and if so, Is there a way to clear it from the ECM so my SES doesn't keep coming On?

If you didn't perform an IAVL (Idle Air Volume Learn) to match the new sensor to the ECM, you need to. P0101 is a "performance" code and not flatline, so there may have been nothing wrong with your old sensor. I've seen "before and after" airflow readings differ by as much as 30% on old vehicles which never had an IAVL since new, simply from the silicon parts in the MAF changing characteristics with old age. This is also a very common cause of poor gas mileage and hesitation issues in older Nissans.

There's also a Nissan TSB for this code if you have no drivability issues along with it. Pull your ECM part number using a scanner, if the firmware p/n has any of the following suffixes then there's an ECM repro that should resolve it:

ZX56A
ZX57A
ZX58A, ZX58B, ZX58C
ZX59A, ZX59B, ZX59C
9HA7A, 9HA7B, 9HA7C
9HA8A, 9HA8B, 9HA8C

How is a IAVL performed?

Will the P0101 eventually cause the TCS light to come on?

With a high-end scanner that does work support. It isn't a lengthy procedure, under 5 minutes on an already-warm engine, so a Nissan dealer should charge no more than half an hour labor for it. They can check your ECM p/n as well, if it needs the repro then an IAVL will be performed automatically as part of the repro process.

PS - I assumed your ride was 4-cyl, if it's 6 then the following ECM numbers apply:

ZX50A, ZX51A, ZX53A, ZX54A, ZX55A
9HA0C, 9HA1C, 9HA2C, 9HA3C, 9HA4C
9HA0D, 9HA2D, 9HA3D

Yes, the ABS will usually throw a speed signal code if the ECM goes limp, so a slip or ABS lamp is likely.

Sorry! It is a 4 cyl. Indo appreciate your help and info. I will just take it to the dealer for the repro.

You're most welcome, happy to help!

Hi Primodlt, Just wanted to let you know, I replaced my MAF sensor 3 times all with a genuine Nissan OEM part and I still got the P0101 code even after replacing them. I went to the dealership to have the ECM reprogrammed and let them know of this bulletin:

https://static.nhtsa.gov/odi/tsbs/2016/ ... 2-9999.pdf

If you can confirm that there are no driveability issues with the car, then this would be why your P0101 code is active even after replacing the MAF.

Just a side note for anyone who gets this code, it very rarely means the MAF is bad. Parts stores tend to assume that, and of course sell a lot of MAF's that way. The fact is, P0101 is a "performance" or "rationality" code, meaning the MAF signal is doing something the ECM doesn't expect (e.g., the signal is irrational). It's not a "flatline" code that automatically indicates a failed component or wiring. The most common causes (if there is no firmware cause) are a dirty or occluded MAF or a small vacuum leak.

In the case of many Altimas and some other models, the programmers at Hitachi simply didn't leave enough "elbow room" in the ECM firmware for A/F and MAF readings that shift with age, so cars may throw P0101's unexpectedly after many years and miles of normal service. That's what the ECM reflash specified by the bulletin actually accomplishes, it increases the "spread" of valid A/F and MAF voltages before the ECM declares them irrational.