Using LS7 MAF with LQ4 harness - pinout differences
Using LS7 MAF with LQ4 harness - pinout differences I am currently running a stock 2003 LQ4 MAF tube in my swap with a 3" stainless pipe going to a small filter. The lump is out of a 2003 Chevy Express 3500, PCM is green/blue connectors. Identical to this:
Here is what my connector looks like:
I'd like to move up to a 4" intake tube for better throttle response, which requires the use of a different MAF sensor as mine cannot be removed from the tube. So, I purchased the following:
LSX MAF Bung (weld in, aluminum)
and LS7 MAF, GM PN 15865791
It appears that although the 5 pin connector is physically the same between the LQ4 MAF and the LS7 card MAF, the pinout internally is different (according to research about this general procedure).
LS7
Pin - Wire - Circuit - Function
A - 0.35 YE - 492 - Mass Air Flow (MAF) Sensor Signal
B - 0.8 BK/WH - 451 - Ground
C - 0.5 PK - 539 - Ignition 1 Voltage
D - 0.35 TN - 2760 - Low Reference
E - 0.35 TN - 472 - Intake Air Temperature Sensor Signal
Does anyone have any input on the LS7 MAF pinout differences as compared to a stock 2003 LQ4 MAF harness? I have no problem swapping wires, just need to know what the pinouts are.
Here is what my connector looks like:
I'd like to move up to a 4" intake tube for better throttle response, which requires the use of a different MAF sensor as mine cannot be removed from the tube. So, I purchased the following:
LSX MAF Bung (weld in, aluminum)
and LS7 MAF, GM PN 15865791
It appears that although the 5 pin connector is physically the same between the LQ4 MAF and the LS7 card MAF, the pinout internally is different (according to research about this general procedure).
LS7
Pin - Wire - Circuit - Function
A - 0.35 YE - 492 - Mass Air Flow (MAF) Sensor Signal
B - 0.8 BK/WH - 451 - Ground
C - 0.5 PK - 539 - Ignition 1 Voltage
D - 0.35 TN - 2760 - Low Reference
E - 0.35 TN - 472 - Intake Air Temperature Sensor Signal
Does anyone have any input on the LS7 MAF pinout differences as compared to a stock 2003 LQ4 MAF harness? I have no problem swapping wires, just need to know what the pinouts are.
Ok, did some digging and found this post. Halfway down is the MAF pinout for a 2005 6.0 MAF (assuming it is the same as my 2003...)
http://67-72chevytrucks.com/vboard/s...17&postcount=5
So we get:
LQ4
A-------------BK-------------------552----------Low Reference
B-------------TN-------------------472--------IAT Sensor Signal
C-----------BK/WH----------------451--------------Ground
D-------------PK-------------------439---------Ignition 1 Voltage
E-------------YE-------------------492---------MAF Sensor Signal
LS7
Pin - Wire - Circuit - Function
A - 0.35 YE - 492 - Mass Air Flow (MAF) Sensor Signal
B - 0.8 BK/WH - 451 - Ground
C - 0.5 PK - 539 - Ignition 1 Voltage
D - 0.35 TN - 2760 - Low Reference
E - 0.35 TN - 472 - Intake Air Temperature Sensor Signal
Which means I need to do the following pin swaps at my MAF connector for the PCM to read the new MAF properly:
A -> D
B -> E
C -> B
D -> C
E -> A
Can anyone confirm?
http://67-72chevytrucks.com/vboard/s...17&postcount=5
So we get:
LQ4
A-------------BK-------------------552----------Low Reference
B-------------TN-------------------472--------IAT Sensor Signal
C-----------BK/WH----------------451--------------Ground
D-------------PK-------------------439---------Ignition 1 Voltage
E-------------YE-------------------492---------MAF Sensor Signal
LS7
Pin - Wire - Circuit - Function
A - 0.35 YE - 492 - Mass Air Flow (MAF) Sensor Signal
B - 0.8 BK/WH - 451 - Ground
C - 0.5 PK - 539 - Ignition 1 Voltage
D - 0.35 TN - 2760 - Low Reference
E - 0.35 TN - 472 - Intake Air Temperature Sensor Signal
Which means I need to do the following pin swaps at my MAF connector for the PCM to read the new MAF properly:
A -> D
B -> E
C -> B
D -> C
E -> A
Can anyone confirm?
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Thanks for your reply. The issue is not finding a wiring diagram, I have confirmed the pin out. What i am looking for is someone that has done this conversion that can confirm what the ACTUAL pin swap is. I have gotten conflicting information from various forums, people saying to only swap the IAT wires.
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Verdad Gallardo more reading got me this, it looks like I was right. The LS2 connector has the same pinout as the LQ4...
http://forums.corvetteforum.com/1563318191-post7.html
"LS2 pin E to A on the LS7 connector
A to D
D to C
C to B
B to E"
http://forums.corvetteforum.com/1563318191-post7.html
"LS2 pin E to A on the LS7 connector
A to D
D to C
C to B
B to E"
I went ahead and repinned my MAF pigtail this evening according to what I had posted earlier. For some reason my wire colors did not match what was originally posted for a stock LQ4 harness, but this could have been because I screwed up the pigtail a year ago when I got it on the road, and then cut and resoldered it to make it work. Honestly I don't recall what my thought process was back then.
In any event I stuck to the above diagram and repinned the 5. The car fired right up and seemed to run fine (on open headers at least) while it warmed up. I did have a P0102 code thrown, MAF low frequency. My thought is that my pins are wrong, or the tune needs to be changed to accomodate the new MAF scaling for the new unit.
I did take the car out and do a few pulls to see how it reacted. Pulled nice and hard under load but had some pretty serious rev hangs when going into neutral at 60mph+. Also had an occasional serious stumble at idle when sitting at a light, to the point where I thought it would die - however, every time, the revs would come back up to a normal idle (800) and things would be fine again.
I plan on throwing the multimeter on the pins this weekend and finding out what's 5V, what's 12V, etc, to rule out a pinning issue. Tune is schedule for next week.
In any event I stuck to the above diagram and repinned the 5. The car fired right up and seemed to run fine (on open headers at least) while it warmed up. I did have a P0102 code thrown, MAF low frequency. My thought is that my pins are wrong, or the tune needs to be changed to accomodate the new MAF scaling for the new unit.
I did take the car out and do a few pulls to see how it reacted. Pulled nice and hard under load but had some pretty serious rev hangs when going into neutral at 60mph+. Also had an occasional serious stumble at idle when sitting at a light, to the point where I thought it would die - however, every time, the revs would come back up to a normal idle (800) and things would be fine again.
I plan on throwing the multimeter on the pins this weekend and finding out what's 5V, what's 12V, etc, to rule out a pinning issue. Tune is schedule for next week.
I'm doing the same conversion on my car. I was under the assumbption only the IAT wires were different. I do know that I need to swap tables in MAF table though.
The LQ4/9 and LS3/7 MAF put out different frequencies for the same measured airflow as seen in the pic below. This would explain the the P0102 code and maybe idle issues until the active idle tables kick in. I'm def not a good tuner, but I think this could be something to look at once you get the wires starightened out.
I attached an excel sheet to paste into the table. I curve fit the LS3 airflow values onto the LS1b frequency column(they are plus minus a few g/s). You will notice that the LS1b maxes out at 511.9 g/s when it hits 9750Hz. So it seems we lose some resolution when we go to the LS3 MAF.
If anything I've done is wrong, please someone chime in.
Good luck man.
The LQ4/9 and LS3/7 MAF put out different frequencies for the same measured airflow as seen in the pic below. This would explain the the P0102 code and maybe idle issues until the active idle tables kick in. I'm def not a good tuner, but I think this could be something to look at once you get the wires starightened out.
I attached an excel sheet to paste into the table. I curve fit the LS3 airflow values onto the LS1b frequency column(they are plus minus a few g/s). You will notice that the LS1b maxes out at 511.9 g/s when it hits 9750Hz. So it seems we lose some resolution when we go to the LS3 MAF.
If anything I've done is wrong, please someone chime in.
Good luck man.
I think I may have wired it incorrectly. We tried to get some tuning done last night and were not able to get a live MAF reading. It just stayed constant at .562 g/s (or whatever the unit is) despite revs, pulls, etc. My IAT is also stuck at 71F.
I will go back and check continuity for each wire back at the PCM connector, which will correctly identify what the function of each wire is regardless of color, which may be wrong since I modified the harness to work with my setup.
I will go back and check continuity for each wire back at the PCM connector, which will correctly identify what the function of each wire is regardless of color, which may be wrong since I modified the harness to work with my setup.
Sure enough, I had it wired incorrectly. Lesson learned not to rely on random wiring diagrams as you never can be sure of their validity. The multimeter never lies. I went back and depinned all 5 wires from the MAF pigtail. 3 of them were easy to identify, but I made sure by checking their voltage/continuity.
Black was ground - checked continuity with ground circuit on frame
Pink was power - had 12V
Yellow was MAF signal
The last two were IAT signal and low reference wires. I opened up my PCM compartment and pinned #57 on the green connector, which I know is IAT Low Reference according to http://lt1swap.com/2004vortec_pcm.htm
I stuck the other probe into each tan wire at the pigtail end until I got continuity on one of them and had it identified in no time. Got a much more reasonable IAT (102F) after the car had been started a few times on a hot humid day, with MAF readings actually registering now. The car is dropped off for tuning so we'll see how I make out.
Black was ground - checked continuity with ground circuit on frame
Pink was power - had 12V
Yellow was MAF signal
The last two were IAT signal and low reference wires. I opened up my PCM compartment and pinned #57 on the green connector, which I know is IAT Low Reference according to http://lt1swap.com/2004vortec_pcm.htm
I stuck the other probe into each tan wire at the pigtail end until I got continuity on one of them and had it identified in no time. Got a much more reasonable IAT (102F) after the car had been started a few times on a hot humid day, with MAF readings actually registering now. The car is dropped off for tuning so we'll see how I make out.
Sure enough, I had it wired incorrectly. Lesson learned not to rely on random wiring diagrams as you never can be sure of their validity. The multimeter never lies. I went back and depinned all 5 wires from the MAF pigtail. 3 of them were easy to identify, but I made sure by checking their voltage/continuity.
Black was ground - checked continuity with ground circuit on frame
Pink was power - had 12V
Yellow was MAF signal
The last two were IAT signal and low reference wires. I opened up my PCM compartment and pinned #57 on the green connector, which I know is IAT Low Reference according to http://lt1swap.com/2004vortec_pcm.htm
I stuck the other probe into each tan wire at the pigtail end until I got continuity on one of them and had it identified in no time. Got a much more reasonable IAT (102F) after the car had been started a few times on a hot humid day, with MAF readings actually registering now. The car is dropped off for tuning so we'll see how I make out.
Black was ground - checked continuity with ground circuit on frame
Pink was power - had 12V
Yellow was MAF signal
The last two were IAT signal and low reference wires. I opened up my PCM compartment and pinned #57 on the green connector, which I know is IAT Low Reference according to http://lt1swap.com/2004vortec_pcm.htm
I stuck the other probe into each tan wire at the pigtail end until I got continuity on one of them and had it identified in no time. Got a much more reasonable IAT (102F) after the car had been started a few times on a hot humid day, with MAF readings actually registering now. The car is dropped off for tuning so we'll see how I make out.
I'm fighting a P0102 code issue too - engine swap deal and not sure if it is a bad part, tuning issue (mail order tune at the moment pending a live tune), or a wiring problem.
After going through and checking for continuity originating at the PCM, I was able to get the wiring order right, so no wiring issues after that.
My tuner had a tough time trying to re-scale the MAF correctly as well as the IAT. I ended up finding some random IAT tables online that had been put together by other people using an LS7 MAF.
My tune is 8/10 when the car is warmed up - still has an idle/rev hang when not in gear, but moving. When the engine is under 195F, the idle is erratic and wants to stall. I am told this is due to the Chevy Express van PCM being harder to tune - not sure how much truth there actually is to that, so for that reason I'm thinking about having an LS-specific shop take a look at the tune and see what they can do with it.
My tuner had a tough time trying to re-scale the MAF correctly as well as the IAT. I ended up finding some random IAT tables online that had been put together by other people using an LS7 MAF.
My tune is 8/10 when the car is warmed up - still has an idle/rev hang when not in gear, but moving. When the engine is under 195F, the idle is erratic and wants to stall. I am told this is due to the Chevy Express van PCM being harder to tune - not sure how much truth there actually is to that, so for that reason I'm thinking about having an LS-specific shop take a look at the tune and see what they can do with it.