Troubleshooting MAF issue

Mogman

Member
May 3, 2020
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Papalote, TX
I am sorry if this is the wrong place, there does not seen to be a forum for troubleshooting code and sensor issue and allot of folks have them.
Anyway I have a P0102 code, the live data shows 0.0000 lb/min
MAF.JPG


I have ohmed out the MAF cable, confirmed power on key to pin 3, ground on pin 2 and pin 1 to pin 5 of the ECM
With key on or running I get 2.5V to ground on pin 1, It remains at 2.5V not running with key, running or running being revved up, no change, I have confirmed the 5V is coming from the ECM and when there is 12V on pin 3 it pulls the 5V on pin 1 to 2.5V.
When the ignition is turned off and the keyed 12V goes away the voltage on pin 1 rises to 5V until the ECM goes to sleep.
This has been tried with 2 different MAF sensors, the original one and a new one, the pigtail was replaced to the MAF sensor during the stand alone harness build, the IAT works fine which is in the same housing as the MAF
After watching a couple of generic videos about troubleshooting the MAF I expected to see about 1 volt or so at idle and then the voltage moving up as engine rpm increases.
 
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2004LB7

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Dec 15, 2010
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The MAF sensor is frequency based so unless you are measuring it with a scope you will get unreliable information.

Maybe try changing B0204 in your tune to "voltage" to see if the ECM sees anything. Don't know if the ECM is capable of reading voltage on that pin so it may not do anything.

Also, what brand or were did you get your MAF sensors? If you are not using genuine Bosch it may be a bad or incompatible sensor as many off brands or knockoffs are
 
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Mogman

Member
May 3, 2020
311
14
18
Papalote, TX
The MAF sensor is frequency based so unless you are measuring it with a scope you will get unreliable information.

Maybe try changing B0204 in your tune to "voltage" to see if the ECM sees anything. Don't know if the ECM is capable of reading voltage on that pin so it may not do anything.

Also, what brand or were did you get your MAF sensors? If you are not using genuine Bosch it may be a bad or incompatible sensor as many off brands or knockoffs are
AHH! that makes sense, I guess there is a reason good ones cost so much, I do not see any Bosch listed at any of my "local" auto parts stores, Hitachi, A/C Delco (over 300 ouch) and store brands,
I did confirm I could see the MAF data on my other LMM (stock truck) runs about 5 lb/min at idle, the idling MAP was the same on both about 25" and the fuel pressure is about the same at 6K idling.
So ether I have 2 bad sensors or a bad ECM, I may swap some around to tomorrow with the White Elephant (real creative name for the 08 1 ton)
I have stayed away from swapping stuff but the MAF seems safe enough.
I did BTW buy a cheapo MAF, guy has sold over 300 of them not bad if they are crap! I do have a "custom" intake pipe from the filter to the turbo but the air is still passing the MAF in the straightest portion of a 4" OD tube, so it would be reasonable to expect SOMETHING besides 0.000 Lb/Min
 

Mogman

Member
May 3, 2020
311
14
18
Papalote, TX
Tested both of the sensors in the stock truck and both worked, I could read flow in live data and no MIL, also the voltage on pin 1 reacted the same, 2.5V with key on and 5V key off until the ECM goes to sleep, so that only leaves ether a bad ECM or I screwed up the tune.
I am going to dump the HMMWV tune into the white truck, if that works OK I will try the ECM with that tune in the HMMWV to confirm wiring.....
 

Mogman

Member
May 3, 2020
311
14
18
Papalote, TX
Flashed the HMMWV tune into the white truck, no codes and I can see live data air flow, put the ECM into the HMMWV and no codes and I can see live data air flow, put the HMMWV ECM into the white truck and lots of codes and no live air flow data, pretty much raps up a bad ECM, now to find another ECM...
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
Looks like a bad ECM for sure. Get ahold of EFI live to get the ball rolling on a replacement license for your tune to use on the new ECM
 

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