MAF Code (P0101) after new MAF

[bspot]

I got a CEL a while ago, scanned it, P0101- MAF signal out of range.

I logged my MAF values, and the sensor appeared shot, it was spitting the same values constantly.

Put a new MAF in.

Cleared the code. Logged it. Seems to show normal values.

Off I go.

BAM. CEL again last night. Same code. P0101.

I scan it when I'm home, and I can see the MAF sensor sending values that seem to make sense. It looks like it is working fine.

Any ideas?

I have an injen intake the MAF mounts into. It's been on for over a year. I definitely will clean the filter as it looks a bit dirty.

I also didn't unplug the battery after the new MAF, just cleared the codes. Do I need to reset the ECU so the old sensor values are wiped?

[mr2mike]

Vehicle year?

Probably worth trying to use an ODBII computer to clear the codes properly.

If there's filter oil used, that will kill your MAF too if it's coating the MAF.

[bspot]

2007 Volvo S40 T5

I reset the codes with an OBDII scanner. Did not unplug the battery to reset the ECU.

The filter is a dry filter.

[natty54]

I would check for any intake / boost leaks. The code can also correlate to that

[bspot]

I have a boost/vac gauge, and it seems to be reading normal... except it's a crappy autometer that either coincidentally or not, is starting to crap the bed. If I give it a good tap on the gauge though it is ready full vac under engine braking as per usual (just over 20"hg) and about 17"hg at idle (normal for that car) and full bust of about 14psi.

Could a very small leak cause it? What's the easiest way to test for leaks at home?

[natty54]

yes a small leak can cause the issue. Need to make or buy a boost tester and a spray bottle with a soap solution and then spray and visually look for a leak. A bigger leak you should hear a hissing sound.

tool you can make looks like this:

http://www.mirage-performance.com/Ec...aktester02.jpg

engine off maf @ 0kg/h
idle 12-20kg/h
cold engine approx 20 or more kg/h

can check for open circuit and for ground issues

[Toma]

Typical OEM ECU will have a defined range that it accepts from the MAF. Call it .7volts to 3.6 volts as an example.

Now, say you add a bigger inlet pipe (more area), the MAF might read .68 volts to 3.55 volts. The .68 would throw the code.

Also, as mentioned, if you have a vacuum leak after the maf, it will drop airflow through the maf and throw the same code.

Out of curiosity, what are your Short and long term fuel trims logging at idle.?

[bspot]

^After cleaning the filter/resetting the ECU it seems like the code may be gone, but I haven't driven enough to know for sure yet. I've logged MAF values, but next time I will log fuel trims and report back.

Thanks for the help!

[RickDaTuner]

Originally posted by Toma
Typical OEM ECU will have a defined range that it accepts from the MAF. Call it .7volts to 3.6 volts as an example.

Now, say you add a bigger inlet pipe (more area), the MAF might read .68 volts to 3.55 volts. The .68 would throw the code.

Also, as mentioned, if you have a vacuum leak after the maf, it will drop airflow through the maf and throw the same code.

Out of curiosity, what are your Short and long term fuel trims logging at idle.?

This kind of DTC setting is more for process logic, meaning that a certain RPM the engine is expecting to see such and such value, but when it does not the logic determines that there is something wrong.

Another DTC verification method used is one where the PCM sends out 5v (vreff) and the sensor have a built in check value range. all if not all use .5 to 4.5v, so long as the sensor is with in those two voltages, the circuit is fine.
if it sees less than 0.5 then it know there is a short on the signal return wire, if it sees more than 4.5v then it knows there is an open on the signal wire.

another method of determining a fault is by verifying that there is .5v before the engine starts. if there is anything above that value, then the PCM logic knows that there is something wrong with the MAF sensor.

In your case, I would suspect that you have a broken wire, or one that has work hardened and is causing too much resistance either in the power, signal or ground wire.

if you have a wiring diagram, and a multimeter I could give you a few pointers on how to diagnose the circuit

[Toma]

Originally posted by bspot
^After cleaning the filter/resetting the ECU it seems like the code may be gone, but I haven't driven enough to know for sure yet. I've logged MAF values, but next time I will log fuel trims and report back.

Thanks for the help!

Not familiar with the Volvo maf, but some mafs are very sensitive to oil from k%n type filters. If the maf elements have a fuz growing on them, they will also read lean and need a clean.

[cancer man]

Check voltage at sensor.
Check connector at maf for corrosion or loose pins.
fuel pressure regulator.
Smog the system for leaks.
Maf on those cars generally don't fail.
Never buy a knock off either stick with o.e.m or denso.(maf)

How does the car run otherwise?