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2003 Yukon Denali MAF delete

 
Old 12-21-2018, 12:39 PM
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Default 2003 Yukon Denali MAF delete

Iím getting a p0101 code and my Tranmission shifts horribly when the maf is connected. If I unplug it I get a p0102 code and the transmission shifts great.

the engine runs great with or without the maf connected. I know Iíll need to re-connect the IAT sensor if I run without a maf because the truck thinks itís -38f all the time when itís unplugged (iat sensor is in the Maf).

so with the MAF unplugged Iím getting full line pressure in the transmission, the tune is using the factory SD calculations....

i replaced the maf with a known good one and it made no difference. I suspect thereís some issue with the circuit so Iíd like to just cut the wires for the maf leaving the iat sensor wires and entire maf unit where it is.

id like to know if thereís any downside to doing this on a daily driver used for long road trips?

Donít plan on tuning it, hoping the stock SD tune would be ok. I removed the cats but other then that itís totally stock.

if you think SD doesnít work for all seasons or if you think solid shifts are bad for automatic transmissions please donít reply
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Old 12-21-2018, 12:45 PM
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I had a response, then I read the last sentence and I see where this is going.

Cut the MAF out dude. Who needs a stupid *** MAF. Especially when the factory computer uses SD and never used the MAF.

I'm with you, why fix something you can rig up. AMIRIGHT?
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Old 12-21-2018, 12:52 PM
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And why did they put a MAF on it if they just used SD, idiots at GM.
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Old 12-21-2018, 12:58 PM
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Originally Posted by 00pooterSS View Post
I had a response, then I read the last sentence and I see where this is going.

Cut the MAF out dude. Who needs a stupid *** MAF. Especially when the factory computer uses SD and never used the MAF.

I'm with you, why fix something you can rig up. AMIRIGHT?
I do realize the stock tune uses the maf unless itís unplugged and only then uses SD solely. I also realize itís ďbetterĒ with a MAF but I donít want to start throwing parts at it if I can just clip 3 wires and put another 250k miles on it like that.
The second maf I tried was from a parts truck that ran fine when I pulled it...next step is either a brand new maf, maybe a new ECM because the wires all tested fine (got good power and ground to maf) I couldnít test the Hz on the signal wire (not an option on my stupid scanner)
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Old 12-21-2018, 01:01 PM
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Are you in a state that doesn't do state inspections where having a check engine light on will cause it to fail?
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Old 12-21-2018, 01:04 PM
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Originally Posted by 00pooterSS View Post
Are you in a state that doesn't do state inspections where having a check engine light on will cause it to fail?
no inspections at all (hence the deleted cats)
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Old 12-21-2018, 01:06 PM
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Does your scanner have data capability? Assuming not by you saying you couldn't check the hz. I'm curious what the g/s is reading.

My first guess would be a faulty MAF connector, most likely you have a broken wire there at the connector. You can pull on the wires near the connector and if one starts stretching the wiring itself is broken inside the sheathing.

Maybe throw a new pigtail on it before you just run it unplugged and see what happens.

Figuring out the issue shouldn't be too complex, running it unplugged isn't something I would be interested in doing long term.
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Old 12-21-2018, 01:07 PM
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Originally Posted by Lostoned View Post

no inspections at all (hence the deleted cats)

Nice, that's always a bonus. Where are you at that doesn't do emissions inspections?
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Old 12-21-2018, 01:17 PM
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Check the pink wire for battery voltage, use a volt meter and a test light to load the circuit. Check it at the metal terminal in the connector so you're checking the entire connection, if you tap the wire before the connector you won't be checking the wire all the way to the end and the metal pin. Connect a test light and touch it to the pin and touch your volt meter lead to the test light stem so that you see the voltage the test light is getting. If you use a volt meter only and have high resistance it may still show voltage but if the connection is really weak it can pass voltage but not amperage so if you connect the light and volt meter you load the circuit a little bit which makes sure it's doesn't have high resistance, because if you can load the circuit and still get good voltage then it should be good enough for carrying the slight amperage the maf will use.

Do the same with the black wire looking for ground

If all that is good the yellow wire is signal return. I would ohm across the pin to say a foot or so down the wiring.

When doing all these checks bend and twist the connector to see if it blanks out at any time which will show a break in the wiring.

I say all of this because I've seen a few of the connectors have a broken wire right near the connector itself.
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Old 12-21-2018, 01:18 PM
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Also, did you try cleaning yours? They get dirty and skew readings.

The g/s would be really helpful if you can get it.
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Old 12-21-2018, 01:32 PM
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Originally Posted by 00pooterSS View Post
Nice, that's always a bonus. Where are you at that doesn't do emissions inspections?
I do have a scanner to read codes/live data and oddly enough it reads .205 lb and 1.58 g/s when the maf is completely unplugged (iat shows -38) I guess thatís some default it uses when thereís no signal from the maf/iat or maybe thatís a symptom of the problem. I didnít take note of the readings when it was plugged in but I didnít notice anything strange

i was also thinking to change the plug since I got one sitting here from a parts truck but I literally used a magnifying glass to inspect the existing one and it looks mint...the only wire I canít say 100% is good is the actual signal wire since I canít test it but I know itís connected because the maf readings did change when it was plugged in.

im in MN - they had inspections years ago but they learned for every 3 million they spent on inspections they only reduced emissions by like .000000000000000000002% so they shut down the inspection stations and weíve never had any sort of road side inspections except for 18wheelers
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Old 12-21-2018, 01:46 PM
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Originally Posted by 00pooterSS View Post
Also, did you try cleaning yours? They get dirty and skew readings.

The g/s would be really helpful if you can get it.
I actually used a test light, connected from the ground straight to the power wire in the plug as you suggested and the light lit up (also tested ground to battery and positive to frame ground).

Both mafs I have are pretty dirty but the spare I had ďshould beĒ good since it worked fine in the Suburban parts truck I had

i was really shocked by how badly the tranny was shifting, it acted as if it was totally used up, slipping
every shift as if the computer thought I was shifting at 1500rpm when it was actually shifting over 4 grand

Unplugged the maf and it shifts fine again, iím Not 100% sure that issue will go away with the maf plugged in (even if I can fully resolve whatever the issue with the maf is)
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Old 12-21-2018, 01:51 PM
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See what the g/s are with it plugged in and start attacking that. The trans seems to be a by product of what's going on with the MAF so forego fiddling with that until after the MAF is straightened out.

Magnifying glasses don't read ohms, and that's what you need is to ohm out all wiring from one end to the other.

If they are both dirty they are both not reading correctly.

Plug the maf in DIRTY and record the g/s
Then spray it with brake clean or MAF cleaner, use a q tip very gently if need be on the wires to get them clean.
Then read the g/s again and see where it is.

Let us know.
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Old 12-22-2018, 11:03 AM
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Originally Posted by Lostoned View Post
Iím getting a p0101 code and my Tranmission shifts horribly when the maf is connected. If I unplug it I get a p0102 code and the transmission shifts great.

the engine runs great with or without the maf connected. I know Iíll need to re-connect the IAT sensor if I run without a maf because the truck thinks itís -38f all the time when itís unplugged (iat sensor is in the Maf).

so with the MAF unplugged Iím getting full line pressure in the transmission, the tune is using the factory SD calculations....

i replaced the maf with a known good one and it made no difference. I suspect thereís some issue with the circuit so Iíd like to just cut the wires for the maf leaving the iat sensor wires and entire maf unit where it is.

id like to know if thereís any downside to doing this on a daily driver used for long road trips?

Donít plan on tuning it, hoping the stock SD tune would be ok. I removed the cats but other then that itís totally stock.

if you think SD doesnít work for all seasons or if you think solid shifts are bad for automatic transmissions please donít reply
without applying the custom OS and full time failing the MAF in the PCM the car will be in default SD factory mode.

it will use the low octane spark table only, the trans will use max line pressure and it will use the factory VE table for fueling which isnít all that close.

to delete the MAF you need to apply the SD OS. Otherwise youíll have to either put up with or tune around the default operational functions
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Old 12-22-2018, 09:20 PM
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Originally Posted by Luke19901 View Post


without applying the custom OS and full time failing the MAF in the PCM the car will be in default SD factory mode.

it will use the low octane spark table only, the trans will use max line pressure and it will use the factory VE table for fueling which isnít all that close.

to delete the MAF you need to apply the SD OS. Otherwise youíll have to either put up with or tune around the default operational functions
as long as the factory VE table is good enough....close enough then the 02 sensors will make up the difference right? As long as my fuel trims look good then Iíll know if the factory tune is ok correct?

low octane spark table is fine since itíll get low octane fuel only.

when you say custom OS your talking about a custom SD tune right?
OS is operating system in my line of work
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Old 12-22-2018, 09:35 PM
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When you unplug the maf it probably goes into open loop where and doesn't use the oxygen sensors.
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Old 12-22-2018, 09:59 PM
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Originally Posted by 00pooterSS View Post
When you unplug the maf it probably goes into open loop where and doesn't use the oxygen sensors.
not this specific year/vehicle it goes until CL as soon as it warms up even when the MAF is unplugged....that seems strange because the iat sensor was also unplugged but I guess it just uses a default (-38)

i do know that might lead to an over rich Air fuel ratio but thatís easy enough to reconnect by connecting the iat sensor

i just dont donít want to cut the wires for the MAF and regret it later but right now that seems like a logical step...I want full line pressure in the transmission so it seems like a win win

side note: I actually bought the truck to learn HP tuners for a turbo LS engine swap I started so I planned to use SD and tune it but itís 2 credits for the engine and I think another 4 for the tranny...extra $300 dollars in credits is making me want to just spend it on the swap and learn as I go with that
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Old 12-23-2018, 07:04 PM
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Did you try cleaning the MAF and reinstalling it? Have you ohmed from the pin in the connector to a few inches down the wire?

Full line pressure isn't necessarily horrible, it'll keep things from slipping. May cause excess beating on things but I don't hate it myself either.
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Old 12-24-2018, 09:07 AM
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Originally Posted by Lostoned View Post

not this specific year/vehicle it goes until CL as soon as it warms up even when the MAF is unplugged....that seems strange because the iat sensor was also unplugged but I guess it just uses a default (-38)

i do know that might lead to an over rich Air fuel ratio but thatís easy enough to reconnect by connecting the iat sensor

i just dont donít want to cut the wires for the MAF and regret it later but right now that seems like a logical step...I want full line pressure in the transmission so it seems like a win win

side note: I actually bought the truck to learn HP tuners for a turbo LS engine swap I started so I planned to use SD and tune it but itís 2 credits for the engine and I think another 4 for the tranny...extra $300 dollars in credits is making me want to just spend it on the swap and learn as I go with that
you need the IAT input for the airflow algorithm used for fueling, it needs it period. -38 is open circuit and the engine thinks its intake air is -38 degrees. SD needs the IAT input even more so! connect it and stop tuning until you do. youre wasting your time, all data collected and used to edit is void and useless.

cut them where you can re-join them later or get an independent IAT sensor and connect the correct 2 wires.

you don't want max line pressure all the time. you want the trans to use the TCM data to operate it not in default mode.

you want the engine using the high octane table with a correct calibration for your fuel type so that if is picks up detonation it can revert to the low octane table which should be a lower value to protect the engine.... as intended from the factory calibration.

if you want to tune SD and run SD only apply the custom OS... its what its for. stop trying to trick it or cheat, it will never be correct.
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Old 12-28-2018, 04:55 PM
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Originally Posted by Luke19901 View Post
you need the IAT input for the airflow algorithm used for fueling, it needs it period. -38 is open circuit and the engine thinks its intake air is -38 degrees. SD needs the IAT input even more so! connect it and stop tuning until you do. youre wasting your time, all data collected and used to edit is void and useless.

cut them where you can re-join them later or get an independent IAT sensor and connect the correct 2 wires.

you don't want max line pressure all the time. you want the trans to use the TCM data to operate it not in default mode.

you want the engine using the high octane table with a correct calibration for your fuel type so that if is picks up detonation it can revert to the low octane table which should be a lower value to protect the engine.... as intended from the factory calibration.

if you want to tune SD and run SD only apply the custom OS... its what its for. stop trying to trick it or cheat, it will never be correct.
I cut the three wires for the MAF, runs great, shifts great, fuel trims look good (+5.5 both sides, makes sense with the cat delete)

Seems like the MAF is useless on this specific truck unless your worried about emissions (and I am NOT)
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