[Tom Parker]

Hey all. I recently got a Check Engine fault and the scanner told me it was P0101, related to MAF sensor. I went in to have a look and saw a disconnected hose just to the left of the air filter box. There's not much slack or play on the hose so it must connect somewhere within a few inches to the disconnection but I can't see where it goes. Maybe it's supposed to be disconnected? The inner diameter is rather small. Maybe it's a vacuum line? See photo.

Thanks for any help.

 

[VStar650CL]

That's the breather hose for the CVT tranny, it's supposed to be disconnected.

The MAF itself is almost never responsible for P0101's. Parts stores sell tons of needless MAF's that way, but the most common causes are PCV Valves, dirty Throttle Bodies, bad A/F Sensors, or ECM firmware that needs an upgrade. There are bulletins for ECM repros due to P0101 for probably half the Nissan line, and the '13 Altie happens to be one of them. I believe that's a QR25 airbox I see in the pic, so here's a link to the bulletin for the 2.5L:

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static.nhtsa.gov

 

[Tom Parker]

Hey, thanks for the quick and informative reply! Good to know the hose is supposed to be disconnected, so now I can move on to the next step(s), which I wouldn't have known had you not given me that too. Awesome. I very much appreciate your help.

 

[Tom Parker]

Hey, thanks for the quick and informative reply! Good to know the hose is supposed to be disconnected, so now I can move on to the next step(s), which I wouldn't have known had you not given me that too. Awesome. I very much appreciate your help.

Hey, I had one other thought come to mind after my post. My scanner is showing this P0101 as "Permanent". My plan is to do the easy things, like replace the air filter, replace the PCV valve and perhaps clean the MAF sensor. If one of these things fixes it, will that Permanent code go away after erasing it with my scanner? If I fix it, will I know?

 

[VStar650CL]

Various scanners handle DTC's and P-DTC's differently, they're actually stored in different places in the ECM. Regular DTC's are either "Current" or "Past" and will erase immediately once a problem is fixed. P-DTC's only matter if you're in a state like Cali where they hook up a scanner to check them during inspection, and they have to erase themselves by completing a certain driving pattern during which the ECM runs a Self-Readiness Test (SRT). If the SRT is passed then the P-DTC goes away on its own. Many scanners don't discriminate properly between the three DTC types.

Vis your P0101, it's worth trying a new PCV and cleaning the Throttle Body to see if the DTC will clear itself. Very small vacuum leaks can sometimes cause P0101's too, so check for that. I'd also run an IAVL procedure after cleaning the MAF in case your MAF has got out of calibration with old age.

 

[Tom Parker]

Thanks for the pointers. I've got quite a few easy things to check.