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Removing the MAF without a CEL (ODB-II)

Old 11-02-2007, 01:47 PM
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it's my understanding the the MAF signal is a 0-5v signal. the voltage drops as air passes over the heated sensor. As long as the ecu sees a signal on that input, it shouldn't throw a code. but it's a guess. im assuming it would want to see something less than 5v as well, then it would know the sensor is failed.
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Old 11-02-2007, 01:54 PM
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I can test this out for you guys on an NB.
Though I need a O2 simulator to trash my rear O2, it's throwing a CEL right now.

EDIT: Might try this http://www.mkiv.com/techarticles/oxy...sor_simulator/ unless you all know of something easier.
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Old 11-02-2007, 03:12 PM
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Why cant I just plug the megastim into all of the required ports on my ECU while its connected to a 9 volt battery and take that to be inspected. :(
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Old 11-02-2007, 03:17 PM
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not even close.
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Old 11-02-2007, 03:46 PM
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Originally Posted by Braineack View Post
not even close.
Can I make a seperate thread to discuss this, or will it breach VBul or forum rules?
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Old 11-02-2007, 03:49 PM
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all the stim does is send fake signals to the megasquirt so you can make sure it's operational. that's it. it requires removing the db37 harness, in that case it will not manipulate any of the signals to the car.
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Old 11-02-2007, 03:53 PM
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Originally Posted by Braineack View Post
all the stim does is send fake signals to the megasquirt so you can make sure it's operational. that's it. it requires removing the db37 harness, in that case it will not manipulate any of the signals to the car.
Yea I know what the megastim does, but think about it.

Why cant I make a megastim like device, maybe even use the megastim itself, to provide the factory ecu with the proper signals? Lets make it even simpler, we can use a real MAF and EGR Valve to simplify the whole emulation procedure. Why cant I build a computer program for example that will emulate the car, after all the ECU is just another computer.

I am sure im not the first to think about this.
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Old 11-02-2007, 03:56 PM
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you dont thinks that's more trouble than it's worth?

how about removing the MAF 364 days out of the year.
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Old 11-02-2007, 04:09 PM
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Originally Posted by Braineack View Post
you dont thinks that's more trouble than it's worth?

how about removing the MAF 364 days out of the year.
No I don't in fact. Its not just replacing the MAF for 1 day of inspection. More things tie into that, what if you are running catless, or a full standalone. Its easier for you, your car is pre obd2 all you gotta do is pass a sniff test for the most part. Id love to just bring a box to my mechanic and say, here plug this into your computer and give me my sticker.

According to arkmage, the only other problem he see that may be a problem is the second O2 sensor which calculates a differential from the first O2 to judge health of the catalytic. Now, we are providing the ECU a fake signal that the car is always running properly. The computers calculations would theoretically be off if the second o2 is still providing a true signal.

Two big question though, which will silence me if answers are right.

Just because a car is turbocharged, or supercharged that doesn't necessarily mean that it works outside the normal emissions parameters. Therefore we dont have to worry about the second o2 sensor no calculating properly. That would also mean that the LC1 isnt being programmed to display untrue readings.



Is there anyone, anywhere, passing inspection on a modified OBD2 car who is using a standalone to run fuel and spark?
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Old 11-02-2007, 04:17 PM
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no one will pass running a standalone.
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Old 11-02-2007, 04:35 PM
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Originally Posted by Braineack View Post
no one will pass running a standalone.
I meant in tandem with the factory ecu.

But for the sake of this thread lets discuss a way to emulate the car so the ecu can pass without it.

If I had a wiring harness out of a miata I would already be trying to test this on a bench.

Last edited by Saml01; 11-02-2007 at 04:47 PM.
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Old 11-02-2007, 04:52 PM
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if your two problems are the MAF and rear o2, i dont see why you're making it so hard on yourself. test with the cat and MAF installed.


the rear is just there to simple verify the cat is working, so it's probably making sure the voltage stays within .02v-.08v. something like that.

and you know my thought on the MAF signal.
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Old 11-02-2007, 07:56 PM
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Originally Posted by Braineack View Post
the rear is just there to simple verify the cat is working, so it's probably making sure the voltage stays within .02v-.08v. something like that.

and you know my thought on the MAF signal.
It's a little more complex of a calculation that that... it's looking for a specific voltage offset and phase shift from the front O2 sensor. Other wise people would just stick a resistor on there and call it good. O2 simulators for the rear are cheap though, I don't see the need to reinvent the wheel. This mod is common place and well documented.

I borrowed an oscilloscope from work today, so if I get time Sunday I'll verify if the OBD2 MAF is a simple linear voltage, or a PWM output. Most OBD2 air meters output PWM so I'd be surprised if it's linear.
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