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Old 05-16-2005, 10:12 AM
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Mass Air Flow

I have a 86 Firebird T\A 5.0 efi tpi Im trying to resolve an issue at the maf circuit. I ran diagnostics and the code is 33 mass air flow. Whats happening is there is continuous power to this sensor thus ends up draining the battery. This car was purchased from 1st owner about a month ago. He said brand new relays were installed. I still feel that there is a relay and it is stuck or something. Any info that you might have about this would be very helpful. Also when the terminals are shorted out going into diagnostics is it normal for the radiator cooling fan to start running????? There is a problem with vehicle overheating and I believe that it is due to the maf, or cooling fan or both. I have spoke with a part stores and they dont know anytyhing at all. Im in dire need to resolve this so my wife can use this car to go to work. Your help would be much appreciated. thank you Luke

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Old 05-16-2005, 04:39 PM
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Maf

doc here,

I Do not have a diagram for your specific Vehicle...I do however have one for an Early/Mid 80's Corvette With MAF...and according to it...

You do not have power coming from an outside source..OR through a relay..It is directly supported by the computer...and fed in series with the throttle position sensor...Oddly enough, the coolant temp sensor is located on the other side of the TPS...

But All of these are isolated to the computer signal terminals...not supported from an outside power source.(At least in THAT drawing..yours may differ) You could try pulling the computer Fuse (S) and see if Power goes away. If so it may be internal to the computer (not field serviceable) or you may have a miswire...(Or on your specific model..be normal)

You need to get a Manual For your car at the auto parts store, and check the diagram for the MAF to Computer Hookup..Check it for outside power sources..If you can't make heads or tails of the drawing, Scan it & post it here, and we can help you more..

Are You sure the MAF is draining the battery? I can not see it as a power drain with a high enough draw to allow that (without burning up the sensor itself) You may have 2 separate problems...Like a bad diode pack on the Alternator or a bad Regulator diode pack..Causing a drain through the alternator while sitting...

A simple test is put a Volt/Ohm meter across the battery terminals while running the engine..is it 14.4 volts? If any lower than 13.75, or around 11 volts...The Alternator is bad...and is only partially supporting the Electrical system..If that has happened, and a Diode has failed and reverse biased allowing a small amount of AC into the system,from the malfunctioning diode (1 of 3 or 6) and that COULD hose the computer..or at least Code it...Depending on how bad the Diode (s) are depends on weather or not you get a Battery or low voltage light..

Another simple test to do while getting a manual for the car..is pull the MAF sensor plug and let it sit overnight (or an equal amount of time required to run the battery dead) If it is dead the next day..you have another problem (in conjunction with, or separate to the MAF)

Sorry I couldn't be more help on this one, but maybe someone out there has a diagram or actual experience with your system and more advise on where to look....Or if you get (or Have a manual) post it here, and we can be of more help for you.

Doc
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Old 05-23-2005, 01:24 PM
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Quote:
Originally Posted by HerTA
I have a 86 Firebird T\A 5.0 efi tpi Im trying to resolve an issue at the maf circuit. I ran diagnostics and the code is 33 mass air flow. Whats happening is there is continuous power to this sensor thus ends up draining the battery. This car was purchased from 1st owner about a month ago. He said brand new relays were installed. I still feel that there is a relay and it is stuck or something. Any info that you might have about this would be very helpful. Also when the terminals are shorted out going into diagnostics is it normal for the radiator cooling fan to start running????? There is a problem with vehicle overheating and I believe that it is due to the maf, or cooling fan or both. I have spoke with a part stores and they dont know anytyhing at all. Im in dire need to resolve this so my wife can use this car to go to work. Your help would be much appreciated. thank you Luke
If you have not got this fixed as of yet I can fax you a wire diagram of the MAF set up and also the trouble flow chart for your code # 33. Just let me know the # to fax it to if you still need help. Or if I can help out in any other way just ask.

Steve
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Old 05-23-2005, 10:34 PM
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1) It is normal for the fan to run during diagnostics
2) The MAF sensor for that year had a 'burn off" mode, where the sensor would get superhot for a short time to burn off crud that built up on the sensor. Gm had a little trouble with that design.

I do not have a wiring diagram at hand either, I suggest you take 1931 steve up on his offer.
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