P0102 Wiring good, replaced MAF, still reading 0.00 g/s

[KillyMcGee]

Went thru these steps:
1: Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms between the MAF low reference circuit terminal 2 and ground. If greater than the specified range, test the MAF low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. .4 ohms

4. Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms between the IAT sensor 1 low reference circuit terminal 4 and ground. If greater than the specified range, test the IAT sensor 1 low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. .4-.5 ohms

5. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 and ground. If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. ~11v volts with key on engine off, and ~14 volts with engine running

6. Ignition ON, test for 4.8-5.2 volts between the MAF signal circuit and ground. If less than the specified range, test the MAF signal circuit for a short to ground or an open/high resistance. If the circuit tests norm 5v here


I tested pins 1,2,4, and 5 to ECM and wiring is good.
Pin 3 would appear good since voltage matches batter minus a small bit
I replaced MAF with a new one (don't have but one truck or one friend with LMM so can't swap known good parts) and my Snapon Solus reads 0.00g/s

IAT1 (in MAF) read close to outside air temp
IAT2 read a degree or 2 different.

I get P0102 upon startup of vehicle. Cleared and it comes back. Reduced power mode comes on.

Its a family members truck, bought it used and says it has a tune on it. It has a 5 position switch on the dash but I can tell no difference at idle on the 5 tunes and didn't want do dog on it too hard to see if I could tell a difference going down the highway. Nor does either of us know what 1-5 are so I am hesitant to just test them out.

Truck has a full exhaust and a DPF delete. It also appears to have EGR removed and blocked off. I'm not familiar with Duramax's, thats why I'm here. I appreciate any help.

 

[2004LB7]

do you have a scan tool that can read the maf voltage pid? if so short maf pins 1 and 3 together and see if the ECM can see the voltage

 

[KillyMcGee]

do you have a scan tool that can read the maf voltage pid? if so short maf pins 1 and 3 together and see if the ECM can see the voltage

Short the 5v reference and the 12v supply together?

 

[Ron Nielson]

This is for my 2008 LMM. Pin 1 is the signal out, pin 3 is the 5V ref coming in.

 

[2004LB7]

Short the 5v reference and the 12v supply together?

there shouldn't be any 12 volt. there is a 5 volt supply (pin 3) and ground (pin 2). this is what the MAF sensor uses to power itself and generate a signal with. then it sends the signal down pin 1. by shorting the 5 volt supply pin 3 to the signal pin 1 you would be sending 5 volts down to the ecm. if the ecm is working properly it should set a new code. you should also see this 5 volts on a scanner capable of reading the correct pid. all this is to verify the ECM as you said all the wires are good. there really is only three things to this, the ECM, the wires and the sensor. rule each one out one at a time and you will find your problem

 

[KillyMcGee]

I'm sure its me that is confused but I'm trying here.

Pin 1 is MAF signal. Should be 5V. Pin 2 and 4 are ground. Pin 3 is ignition voltage and pin 5 is IAT signal.

Test #5 says pin 3 to ground should light a test lamp.

 

[2004LB7]

"ignition voltage" might be the wrong terminology as it's not 12 volts. it is 5 volts and is supplied by the ECM. this would be present for pin 3

yes, 2 & 4 are ground

MAF signal on pin 1 is a frequency based signal so it may not read correctly on a regular meter. this signal is generated by the MAF sensor and sent down pin 1 to the ECM. if the MAF sensor is not plugged in it should read zero volts.

 

[KillyMcGee]

#6 above: Ignition ON, test for 4.8-5.2 volts between the MAF signal circuit and ground

This is my Yellow wire and I get 5 volts to it with nothing plugged in.

My pink wire (center #3) I get ~battery voltage to it with nothing plugged in.

its late and I'll double check these if I'm able tomorrow.

I'm 100% sure that I got 12 volt on pin 3 today with MAF unplugged on harness. Just want to make sure whatever is broken before I throw money at more parts.

 

[2004LB7]

hmm. I'll probably have to check that against my LMM. didn't think there was any 12 volts there. but that document seems to indicate there should be. also the 5 volts on the signal wire. it kinda makes sense if it is that way as much of the other circuits are controlled by a switched ground so maybe the MAF dumps the 5 volts to ground?

 

[2004LB7]

ok, just checked mine

pin #1 = 5 volts
pin #2 = ground
pin #3 = 12 volts

so maybe the MAF sensor does dump the pin 1 voltage into ground via a frequency controlled circuit and the ECM can see this. seems odd but I guess it works

 

[Ron Nielson]

The below is from the P102 information. I believe this is not understood, at least not by me.

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based signal on the inlet airflow through the sensor bore. The frequency varies in a range depending on engine coolant temperature (ECT) sensor 1 of approximately 2,300 Hertz at idle to near 9,000 Hertz at maximum engine load.

There appears to be 12V input to the MAF on pin#3. Perhaps my failure to understand has to do with the Wiring diagram notation of 5V at the ECM for pin#1. Is there also input on Pin#1?? How does this work?

 

[2004LB7]

confusing for sure. my only guess is that the MAF sensor pulls pin one to ground at a varying frequency

 

[KillyMcGee]

What snappn says about it.

Plus you can see my mad readings that never change.

 

[KillyMcGee]

Also, what voltage do you guys get when you are running, harness plugged in to pin 3(pink). I get batter voltage minus 1 when unplugged from maf, and 1.6 when plugged in. Replaced maf again to see if it was a bad part. Not likely

 

[KillyMcGee]

Spamming this with new posts, sorry.

Fixed the issue. Had 13v on pink wore until I plugged it in, then the voltage dropped. Cut the wire and supplied battery voltage straight from the positive terminal and p0102 went away and MAF reads within spec.

 

[2004LB7]

sounds like a bad connection at one of the connectors, corrosion at the connection or a broken wire barley making contact. once a load is applied the wire can't support the current so the voltage drops

 

[HylianKnight1997]

Spamming this with new posts, sorry.

Fixed the issue. Had 13v on pink wore until I plugged it in, then the voltage dropped. Cut the wire and supplied battery voltage straight from the positive terminal and p0102 went away and MAF reads within spec.

How did you test it while it was plugged in? You can't get to the terminals?

 

[Chevy1925]

How did you test it while it was plugged in? You can't get to the terminals?

Almost a 2 year old thread my man.