Still getting MAF codes after Replacing MAF sensor

I just bought a 2005 legacy outback XT with a swapped 2.0l engine and some small mods. T also came with a tuning chip that I’m not sure is helping or adding to the problem. Everything was fine except the maf sensor and air intake temp sensor were throwing codes. It wouldn’t idle for more than a few seconds without killing the engine, so I drove with it unplugged until I got a new maf. Fast forward like 2 days I got a new maf sensor and Edelbrock air filter. Disconnected the battery for about 30 mins after installing. It idled and drove okay for a bit and cel was ofd but after about 10 minutes of driving it went limp and killed the engine and the power steering and was throwing MAF codes again but not air temp codes. Anyone have an idea if it’s actually the sensor that’s bad or if it’s the 2.5l ecu being thrown off by the 2.0 engine? Or if there’s some other possibilities like wires, harnesses, or fuses? I’m super new to cars and I’m not sure where to start and I’m on a pretty tight budget so I’d appreciate some insight and advice before I start throwing money at the wrong issues. Thanks in advance.

Oh man, shaking head. With all of the “mods” and “tunes”, and especially non-original engine, you’ve got all kinds of variables.

This is going to be a whole mess of problems. It’s not going to be cheap. Can you return the car?


No I can’t return it, it’s not a bunch of mods, really it’s just the swapped engine and a different exhaust. Why is the different engine such a big problem other than the ecu difference?

I’d bring the vehicle back and demand a refund.

And if the seller gives you a hard time, tell them you’re going to report them to the EPA and the state for tampering with emissions.



Did it every run correctly after the engine swap and tuning mods?

If not, I suspect you are going to have to secure a 2.0L engine powertrain computer. There’s no reason to believe software for the 2.5 would work correctly on the 2.0. It’s possible the existing computer can be reconfigured though. You’d have to ask at a Subie dealership or Subie specialist shop.

[deleted paragraph about MAP, not relevant to OP’s car]

Before you give someone advice, you should know how something works.

Before replacing a Mass Airflow sensor, it’s a good idea to test it. Depending on the engine size, the MAF’s PID value should be between 2 to 7 grams/second and between 15 to 25 grams/s at 2500rpm .


Sorry OP, confused MAF w/MAP. I deleted the paragraph above about the MAP.

Unfortunately I can’t bring it back. I’m just looking for a solution. Even if it isn’t cheap, what kind of repairs would I need to make to get it running correctly? Would I have to replace all the other components in the engine bay or is it something a professional tuner could solve by making some adjustments or reconfiguring the ecu?

Install the correct engine.


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Does it still drive with the MAF unplugged? Have you tried a stock intake and air filter? Are you using a MAF for the engine that is currently installed (2.0)?

A custom tuner might could sort this out. I have seen them plop 6.0 GM’s in the place of 4.8 liter GM’s using the 4.8 ECM with custom tuning. But, that is not a Subaru, and I have no idea what a custom tuner would charge to program it. There may be differences between the 2.0 and 2.5 engine that are not accounted for with whatever tuning chip is in it. Chips aren’t much of a thing anymore. Usually they just change the parameters in the ECM with a laptop plugged in to the diagnostic port. So I’m a little skeptical of the chip…

@ryanbeazer69 - can you answer this question?
Who did the swap and mods? Was this a pro shop? Or a shadetree mechanic? Or Joe Blow in his front yard?

I’m going with…Joe blow in his front yard.


Sorry if this come off rude I’m not trying to be. But I’m not looking for a stock car. How would I learn anything without running into some issues? I’m just looking for what I need to do to make this engine run in this car. I’m a hands on learner and I’m just getting into it and trying to understand how everything works. If I absolutely need to swap it back to a ej25 I will, but as of now I’m more or less wondering if I could either put a different ecu in or get a tuner to remap the 2.5 ecu already in there? Would that be possible or not?

Yeah it runs with the maf unplugged and it gets mewhere it needs to but it obviously runs rich and I don’t want to push it for too long like this

The tuning chip is garbage and isn’t a big part of my issue, just thought I’d mention it as part of the car to give a bit more info. Everything else in the car has been running perfectly. Just tryna figure out how to fix the maf issue

Look for a good foreign car tuner in your area. they will probably be able to answer your questions better, being they deal with tuning vehicles all the time.

This is pretty much my whole question is if this is a problem a tuner could solve or if it’s something I would have to work on before taking it to get tuned.

Alright. Thank you for actual advice instead of just saying to buy a new car😂

I doubt an improved tuner-chip will do the trick. Best bet – if your goal is to keep the existing engine – is the correct power-train computer. Note that is possible the computer hardware can be retained, just need the engine specific software installed. I don’t have enough experience to know what the best path is though. Best of luck there OP! Sounds like a fun project.

Sorry, I wasn’t clear on the purpose. The reason for first putting the car into a stock configuration is that it “simplifies the variables”. One presumes the stock configuration(s) ran properly, as yours probably did before anything wore out and before mods were introduced. In its present modified and improper running condition, it’s extremely difficult to know whether its problems are “normal failures” or due to the incompatible mods, or a combination, and it could be very expensive in time and $$$ to sort it all out.

By first putting it back to original condition you’ll have something that you know is of solid design and should work, and if problems remain they most likely will be due to “normal” problems one can fix through a combination of diagnostic testing, parts substitution, etc. But you won’t have to deal with the vastly more complex situation you currently are facing, not knowing if problems are caused by simple aging or by the mods.

Once it’s working well when stock, if you desire you can reintroduce mods one or a few at a time. If they work, fine, but if not you always can put the car back to stock and have something to drive while you plan your next step.

The above presumes that you don’t have to invest too much putting it into running configuration. There’s always a chance potential big ticket issues with more subtle symptoms will show themselves once the current ones are fixed (maybe worn rings or an engine that was overheated, leaky head gaskets, transmission issues, center differential, etc.).

Suggest setting a budget for this project, a dollar limit where you will stop - depending on what you paid for it, what you invest just to get it running right might not increase what you can get for it (especially if never get it running right), so try to avoid throwing too much good money after bad.