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I have a 2004.5 LLY that I just found out my mass air flow sensor was not working, but it never threw a code or check engine light? How can this be?
 

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a glitch maybe? How did you find out it wasn't working? I would think it would make the truck run like crap if it wasn't working.
 

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how do you know its not working.....
 

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I was getting the a Suncoast G-Max kit installed. The guy doing the work was having problems with Suncoast's converter not locking up. Suncoast told him to check all the sensor's. That's how he found it.

I had Enervative do tuning and I HAD A PINGING ISSUE. I took the truck to the dealer with the stock ECM to rule out a problem on my end, but all they did was check for codes.
I had lost power and fuel economy since new. Truck did not have the power it had when new!
How do you check the mass air flow sensor if it doesn't throw a code? What kind of test?
 

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I was getting the a Suncoast G-Max kit installed. The guy doing the work was having problems with Suncoast's converter not locking up. Suncoast told him to check all the sensor's. That's how he found it.

I had Enervative do tuning and I HAD A PINGING ISSUE. I took the truck to the dealer with the stock ECM to rule out a problem on my end, but all they did was check for codes.
I had lost power and fuel economy since new. Truck did not have the power it had when new!
How do you check the mass air flow sensor if it doesn't throw a code? What kind of test?
how does he know it "wasnt working"??? I am totally confused. A bad MAF wont cause lockup issues.

If an LLY truely has a bad/disconnected MAF sensor, it will barely even acellerate.

ben
 

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Discussion Starter #7
He told me mine was reading Zero! I'm confused too! I can't believe it never threw a code!
 

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He told me mine was reading Zero! I'm confused too! I can't believe it never threw a code!
I think your guy does not have any idea what he is talking about.

If it is "reading zero" or unplugged, it WILL throw a MAF sensor performance code.
 

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LLY Duramax

I have a 6.6 LLY 2004.5 Duramax and I intentionally unplugged the mass airflow sensor to see what it would do, whether put it in limp mode, more power, smoke a ton, whatever. I unplugged it, and drove about half a mile, no engine light, no limp mode, if anything at all it had slight power gains...
 

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well you're going to have to drive a little more than 30 seconds in order for the ECM to fail the MAF diagnostic....
 

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I had a new air flow system put in my 2007.5 duramax 2500 HD LTZ and it started throwing the mass air flow code, I installed a new mass air flow sensor and it runs fine for about 10 days then throws the code again. I have had it checked by two mechanics and they both say the same thing that it is a bad sensor and think I should put a new one in but they also said it only tigers the code on start up not while running. Have any ideas is there a way to bypass that sensor or does it mean another $ 580 bucks?
 

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My lly throws code as soon as it reaches temp with the maf unhooked.

Anyone know of lly and lb7 are the same? I was keeping the lb7 I have sitting here for a spare. If it won't work I will toss it. They look identical.
 

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Sort of similar issue with my lbz. I was logging one day and noticed my return voltage from the maf was reading zero all of a sudden, however I noticed no difference in drivability or performance, just a tad bit more smoke under WOT conditions however nothing excessive. Unplugged the maf and took if for a ride to see if maybe my scanner was glitching for some reason, same exact result.... which was basically nothing at all really. I've been driving with the maf disconnected for a couple days now and have yet to throw a MIL or notice any drivability issues. I'm going to throw a new maf in her today to see if makes a difference anywhere. It's very strange.
 

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Sort of similar issue with my lbz. I was logging one day and noticed my return voltage from the maf was reading zero all of a sudden, however I noticed no difference in drivability or performance, just a tad bit more smoke under WOT conditions however nothing excessive. Unplugged the maf and took if for a ride to see if maybe my scanner was glitching for some reason, same exact result.... which was basically nothing at all really. I've been driving with the maf disconnected for a couple days now and have yet to throw a MIL or notice any drivability issues. I'm going to throw a new maf in her today to see if makes a difference anywhere. It's very strange.

Does your MAF signal also cut out occasionally when you monitor it?

If so check your reference voltage going to the MAF and look for signs of wire harness damage under passenger side boost tube.
 

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I put in a new mass airflow sensor today and the truck is in for a full work out tomorrow going to pull my 34' fifth wheel with three slide outs up a 7% grade and set it in tow and 65mph see what happens. Before the Mass airflow problem my truck would pull this hill without even breathing hard so I will see if I have the power back. After all the exhaust work and air intake work I have had done no chips I have been running 19 miles per gal. which is pretty darn good for getting an average of 12-14 before.
 

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Does your MAF signal also cut out occasionally when you monitor it?

If so check your reference voltage going to the MAF and look for signs of wire harness damage under passenger side boost tube.
See that's the strange thing. MAF signal has not once cut out in any of my logs. My MAF voltage just stopped showing a reference signal one day (now always reading zero volts), however my MAF flow readings (lbs/min) are still graphing as normal with no breaks or strange readings. I still need to physically check voltage in and out with my meter, but the truck runs fantastic and I'm not getting any DTC's. I would have to think that if there were no actual voltage signal getting back to the ecm that I wouldn't be registering any calculated flow readings at all, and would likely get a maf under voltage or some sort of maf code in general.... but I don't. IDk, it's odd.
 

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See that's the strange thing. MAF signal has not once cut out in any of my logs. My MAF voltage just stopped showing a reference signal one day (now always reading zero volts), however my MAF flow readings (lbs/min) are still graphing as normal with no breaks or strange readings. I still need to physically check voltage in and out with my meter, but the truck runs fantastic and I'm not getting any DTC's. I would have to think that if there were no actual voltage signal getting back to the ecm that I wouldn't be registering any calculated flow readings at all, and would likely get a maf under voltage or some sort of maf code in general.... but I don't. IDk, it's odd.

Your logic is good IMHO, keep looking into it and I'm sure you'll figure out what is causing your issue.
 
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