CEL P0101 Mass Air Flow Sensor

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cc93cruiser

cc93cruiser

CRUZAHEAD
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Feb 2, 2004
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294
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2,745
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Hayward, Ca.
Geez, just fixed my heat exchanger leak on my new to me 09 LX and all was good for about 2-3 weeks and now this.. Took a 200 mile round trip out to the coast with my family and all was good. On the way back home a got a CEL light along with the VSC light and the 4lo light flashing.. I was assuming that the rig was going into some type of limp mode, but nothing.. It drove flawlessly the remaining way home (approx 100 miles), just lights never turned off.. On way home while parked I thought I would give 4lo a try since the damn light kept flashing, but it was a no go... I am assuming this is the limp mode, no 4lo.. I finally got home and plugged in my trusty obd2 scanner and I came up with a single code, P0101-Mass or volume air flow range.. I am assuming the problem lies in the mass air flow sensor? I haven't erased the code from computer. I think I will start with taking air filter box out and intake tube and take a look at mass air sensor, maybe dirty? However, I do have a brand new air filter though... Any thoughts or advice or anyone have this same code come up/fix? I was hoping if everything looks good while inspecting air sensor, I will erase code and hopefully it was some type of computer glitch and truck will live happily ever after.. What you guys think? Here's a couple pics of instrument panel lights that lite up and the code from my obd 2 Torque App...

Screenshot_20170909-203350.webp


20170909_195458.webp
 
Oem Mass Air meter retails for south of 100 bucks, might just swap the bastard out... But is there any chance of cleaning the old one out?

Screenshot_20170909-205917.webp
 
Thought I had this beat, problem came back 2 weeks ago. Oem air filter and everything else checked out. Basically check engine comes on after like 300-500 miles of erasing code with my obd2 app. Truck runs perfect with or without the CEL on. Was wondering if anyone has had this issue with their 200. I am thinking bout just replacing the mass air flow sensor but I'm having doubts about the sensor being bad since the truck runs perfect either way.. Just don't want to buy this and then find out it didn't do anything to fix problem.. Any thoughts? Do these sensors go bad over a period of time and not right away, explaining why rig is still running fine?
 
The sensor may be reading out of range, which would trigger a code, but if it's not way out the engine will run ok. When you use cleaner, use the real stuff and not just the leftover can of something you have on the shelf.......

https://www.amazon.com/CRC-05110-Mass-Sensor-Cleaner/dp/B000J19XSA/?tag=ihco-20

If cleaning doesn't do it, spring for a new one. And make sure your air filter airbox has a good seal and that the intake to the airbox is clear.
 
I might get heat for this, and I don’t like mentioning things that could waste money, but here’s my opinion.

Some years back when I got really crafty with replacing Toyota ECUs with my own, I found that the O2 and air/fuel sensors with over 100,000 miles would not read very accurately, yet they would never through a code on their own. I had the same issue as you once and chased it to the MAS, and found that that sensor also didn’t read very accurately past 100k. Now I’ll be there first to say, no, it’s not a priority, it’s just something I feel I like to do, escpecially beciae it only costs me about $250 and I do it every 10 years or so per vehicle.

Long story short, I’ve fixed a few other friends with your issue the same way. Not a ton, just a few, so take this with a grain of salt.

Either way, I replace my MAS, O2, and air/fuels with my spark plugs, at 120,000 mile intervals because of the benefits I’ve seen on my tuning PC.
 
TonyP said:
Pull the sensor and blast it with some MAF cleaner to see if that helps.

Click to expand...


Sandroad said:
The sensor may be reading out of range, which would trigger a code, but if it's not way out the engine will run ok. When you use cleaner, use the real stuff and not just the leftover can of something you have on the shelf.......

https://www.amazon.com/CRC-05110-Mass-Sensor-Cleaner/dp/B000J19XSA/ref=sr_1_1?s=automotive&ie=UTF8&qid=1514939329&sr=1-1&keywords=mass+air+flow+cleaner&th=1

If cleaning doesn't do it, spring for a new one. And make sure your air filter airbox has a good seal and that the intake to the airbox is clear.
Click to expand...
Been there done that.. Bought the MAF cleaner and cleaned just about everything including sensor...Code still comes up...
 
Taco2Cruiser said:
I might get heat for this, and I don’t like mentioning things that could waste money, but here’s my opinion.

Some years back when I got really crafty with replacing Toyota ECUs with my own, I found that the O2 and air/fuel sensors with over 100,000 miles would not read very accurately, yet they would never through a code on their own. I had the same issue as you once and chased it to the MAS, and found that that sensor also didn’t read very accurately past 100k. Now I’ll be there first to say, no, it’s not a priority, it’s just something I feel I like to do, escpecially beciae it only costs me about $250 and I do it every 10 years or so per vehicle.

Long story short, I’ve fixed a few other friends with your issue the same way. Not a ton, just a few, so take this with a grain of salt.

Either way, I replace my MAS, O2, and air/fuels with my spark plugs, at 120,000 mile intervals because of the benefits I’ve seen on my tuning PC.
Click to expand...
Will must likely go this route, minus the O2s.. Currently have 93k so was going to swap out spark plugs and MAF sensor.. I will also be replacing the pcv as that has never been replaced. IIRC I think I read somewhere that some tundra owners were having similar symptoms on their 5.7s with the original pcv valves...
 
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Gents, just had the exact same thing happen ('10 LX - 135k) at about the 250 mile point on a 330 run we do pretty frequently in the summer BUT have not done since last fall.

Called dealer (excellent tech) and he thought I might have a fuel cap issue. Stopped at Advance Auto and pushed P0101. Dealer closed by time I pulled the code - not in until Mon.

Is the general consensus it is the PCV?

Truck runs fine - just not liking the dash "light show"
 
LXinOBX said:
Gents, just had the exact same thing happen ('10 LX - 135k) at about the 250 mile point on a 330 run we do pretty frequently in the summer BUT have not done since last fall.

Called dealer (excellent tech) and he thought I might have a fuel cap issue. Stopped at Advance Auto and pushed P0101. Dealer closed by time I pulled the code - not in until Mon.

Is the general consensus it is the PCV?

Truck runs fine - just not liking the dash "light show"
Click to expand...
same exact symptoms... I would swap the pcv valve it has never been done (mine was shot).. It literally is a 10 min job...Have over 2k miles since replacing valve, CEL never came back...
 
Btw, have you connected a obd2 scanner to it?
 
Yep, same code (pulled into an Advance Auto and got P0101). AZ data base said mass flow? WTF? I mean how are they connected to the VSC and, even more random, 4WD Lo? Anyway, the guys allowed me to use their PC and google pulled up (of course, iH8mud) your post.

Did you have to reset or did your "lights" extinguish after driving a while - after replacing PCV?

Also, did you ever try cleaning the valve first (so the little ball moves freely?)

Sidebar - I've never, save an 40 series in the '70's, had to change a PCV

Thanks, cc93, appreciate the feed back (btw, was just in Hayward this past Weds!)
 
As I recall - positive crankcase ventilation - so positive pressure gases in the valve cover can escape - allows vapor to only go one way. At least that's what I remember - it was , after all, 40 years ago....
 
Oiled air filters, pick your poison, have a reputation for coating MAF sensors and of course disrupting the temperature drop so that it is out of tolerance. I tossed oiled filters for everything in my garage except carburetor motors. Yes, you can use a K&N but you have to be careful about the amount of oil. The OP did not mention what kind of air filter was employed.
 
Anyone know who is the oem supplier for toyota on the Mass Air Flow sensor on the 200 series? Took mine off and it says Hitachi Made in Japan...Wondering if this part had been replaced with an aftermarket unit or is this oem part...Hitachi part number MAF0103
 
That is the correct oem unit..... Make sure you clean out your throttle body too with some cleaner....After replacing my mass air sensor, cel would still come on... After after busting out the FSM, I decided to check anything that might cause this issue (vacuum hoses/pcv etc) and cleaning the throttle body blade really well did the trick....
 
Reviving an old thread to add one more data point for P0101 on a 200-series/LX570.

My symptom pattern was very similar to this thread: P0101 appeared during steady highway driving, with the usual CEL/VSC/4LO light show, but the truck continued to drive normally. Restarting did not clear the code.

I pulled the MAF sensor first. The MAF looked essentially clean/new, with no visible dirt or oil film. The air filter also looked very clean, with only light normal discoloration.

Then I removed the PCV valve. That was a different story. The valve was heavily coated internally with an orange/brown clay-like deposit. It did not rattle or feel like the internal valve was moving. Under an illuminated stereo microscope, I could see a substantial amount of gummy/clay-like deposit inside, and the valve appeared to be stuck open. After scraping out the gunk, followed by solvent immersion/cleaning and observation under the microscope, the internal valve broke free and again moved through its full stroke, with spring return.

The throttle body was also quite dirty, in stark contrast to the very clean MAF and air filter.

My current interpretation is that the P0101 in my case was probably not caused by a dirty MAF. It looks more like a PCV/throttle-body airflow plausibility problem: the PCV valve was stuck open, allowing excessive/uncontrolled crankcase ventilation flow under vacuum, and the related oil vapor/blow-by contamination likely contributed to throttle-body deposits. Together, that could disturb the expected relationship among MAF reading, throttle angle, RPM, load calculation, and fuel trims enough to trigger P0101.

I am not treating the cleaned PCV as a permanent repair; I plan to replace it with a new OEM PCV valve. But the inspection result is strong enough that I would recommend checking the PCV valve, PCV hose/seal, and throttle body before replacing the MAF on a 200-series/LX570 P0101, especially if the MAF and air filter are visibly clean.

With the dashboard power fully on but the engine not started, pressing the gas pedal opened the electronic throttle plate, which made it possible to clean the area behind the plate.

My 2008 LX is at 135k miles. The PCV looked like the factory-installed part; the surrounding foam insert was still completely intact.

I will update again if the story changes after some road miles.
 
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