Prius 2010 check engine code: P0101: Mass or Volume Air Flow Circuit Range/Performance

There are eight pages in the Repair Manual (more info) on troubleshooting that code. As always, you could get a sensor code because something is off about the sensor (the conclusion many people jump to) or because something is off about what the sensor senses (in this case the amount of intake airflow compared to what's expected for the engine load). That could lead to exploring for intake leaks, EGR stuck open, etc. It'll probably be faster / more satisfying to follow the troubleshooting steps in the manual and just find where the problem is and fix it, than to keep swapping parts.

 

This type of error is very basic in engines these days. It’s not Prius-specific at all.

The car’s computer measures how much air is entering the engine using two sensors: MAP and MAF. The MAF sensor is at the top of your air intake, on the top of the air filter housing. Make sure the electrical plug is attached, for starters. You can clean it, but it probably doesn’t need to be cleaned or replaced.

After combustion, one or two oxygen sensors measure the oxygen in the exhaust, to determine the fuel trim level — do we need more or less air to fuel. You can use your scan tool to view the short term and long term fuel trim levels, which can help you troubleshoot. Vacuum leaks can cause these errors — a dipstick not fully inserted, or a bad o ring on the dipstick, for instance. Prius doesn’t have a lot of other vacuum leak vectors, though. No vacuum hoses at all.

There are a lot of YouTube videos about this. i like the Schrodinger’s Box videos.

 

Don’t walk, run away.

 

Don’t walk, run away.

To where?

I think the concern about understanding the repair manual link was that it is written in English. Does Phnom Penh, Cambodia have an English speaking or reading Toyota repair facility to try? Maybe an area that has a very large tourist population? If you can find a Toyota place, maybe they can at least do a good diagnostic.

 

Does Toyota have another online site with a different translation of the manuals?

 

I’ve listed all the public or subscription websites I know about on the Wiki page; there are other websites accessible only to Toyota dealers and distributors.

As far as I know, Toyota prepares only one translation for each language; I’ve never seen a Toyota service document in Basic English or ASD-STE100 Simplified Technical English, for example. I don’t know if a Khmer version of the third-generation Prius Repair Manual exists, but I doubt it, since the Toyota distributor in Cambodia doesn’t seem to sell new Prius cars.

 

This problem is NOT about Toyota!
All modern engines have this issue: This is basic engine management used by Toyota, GM, Nissan, Ford... everybody.

 

I see part of the troubleshooting for P0101 is to check the condition of the EGR system. Since that's a known-to-clog factor, maybe check that. Note too, the bulk of the troubleshooting involves use of Toyota proprietary Techstream software.

How many miles on it btw?

EGR info follows (and some attachments):

The simplest way to see where you're at, is to check the degree of carbon build up in the EGR pipe, a stainless steel connecting pipe between the EGR valve and intake manifold. Watch @NutzAboutBolts video #16 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

Two or three other videos linked there too, for the full cleaning of the intake manifold, full EGR clean, and Oil Catch Can install.

Good thread:

EGR & Intake Manifold Clean Results | PriusChat

Another:

Oil Catch Can, Eliminate that knock! | PriusChat

Some tools worth having:

E8 Torx socket (mandatory)
E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
3/8" ratchet wrench, regular and long handle, flex head, you can never have enough (or 1/2 plus reducer)
1/4" ratchet wrench, or 3/8" to 1/4" reducer
Ratchet extensions: you can never have enough
Long needle nose piers, straight and bent tip
Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
Torque wrench (3/8" and 1/4" both good to have)
Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.

 

By the same token, in a twist on a favorite PriusChat theme, in this case it is about checking for a valve stuck open and supplying too much EGR.

 

Most check engine codes require three full Startup/Warmup/Drive/Shut down cycles until they make the CEL come on. As I’ve said, there is nothing Prius or hybrid-related about this error. Every gas-powered car sold today can have this error.

 

The CEL can also take multiple start up before it'll go away I think. In other words, after trying something to resolve the issue, give it a while, the CEL may persist for the next while, even though you've solved the problem.

 

Did you fix your car? If yes what was the peoblem?

 

My problem with P0101 solved, i had after market Air Box which my MAF sensor did not fit inside well , i bought top cover of air intake box from salvage yard and everything works properly now.