Lm7 maf - iat
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Joined: Dec 2025
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Lm7 maf - iat Engine runs but have a P0102 code.
Probably not the first one asking this but have not been able to find what I’m looking for.
Donor: LM7 Tahoe 2003 blue/green pcm
MAF/IAT 25168491
Drive by wire throttle body.
Harness ”cheap Amazon” blue/green
I can identify pins with 12v 5v and ground on MAF/IAT 5 pin connector.
Question 1:
Left to right should be as below, am I correct?
1 - MAF
2 - ground
3 - 12 volt ignition
4 - 5 volt reference
5 - IAT
Question 2:
How can I verify cabling in harness for MAF and IAT signal? I can’t find a table for that, do they connect straight to any PCM pins? which pcm pins or how shall I trace cabling?
Probably not the first one asking this but have not been able to find what I’m looking for.
Donor: LM7 Tahoe 2003 blue/green pcm
MAF/IAT 25168491
Drive by wire throttle body.
Harness ”cheap Amazon” blue/green
I can identify pins with 12v 5v and ground on MAF/IAT 5 pin connector.
Question 1:
Left to right should be as below, am I correct?
1 - MAF
2 - ground
3 - 12 volt ignition
4 - 5 volt reference
5 - IAT
Question 2:
How can I verify cabling in harness for MAF and IAT signal? I can’t find a table for that, do they connect straight to any PCM pins? which pcm pins or how shall I trace cabling?
https://charm.li/Chevrolet/2003/C%20...20Diagram%202/
IAT should have a low reference, not a 5v pin
12v and grd are reversed on the MAF portion. That's important
The two IAT wires can be reversed without issue
P0102 is typically a bad MAF code, but if the wiring is incorrect, then it will always flag
I'd swap the two pins for the MAF and confirm the IAT isn't actually low ref to the PCM. If it is truly 5v, then you're digging deeper into the harness. Honestly, expected for the low buck garbage wiring
IAT should have a low reference, not a 5v pin
12v and grd are reversed on the MAF portion. That's important
The two IAT wires can be reversed without issue
P0102 is typically a bad MAF code, but if the wiring is incorrect, then it will always flag
I'd swap the two pins for the MAF and confirm the IAT isn't actually low ref to the PCM. If it is truly 5v, then you're digging deeper into the harness. Honestly, expected for the low buck garbage wiring
Thread Starter
Registered User
Joined: Dec 2025
Posts: 3
Likes: 2
Thanks for your help Pocket! much appreciated!
When I planned my project I had the ambition to modify a stock harness, some work but quality harness I figured. When I got the engine and trans I was talked into buy it with a stand alone harness, seller praised the quality. Let’s say I regret that. Already when I opened the box and looked at the ”instruction”.
PIN 57 was connected to IC 8
PIN 25 was going to a loose end in harness
IAT was connected to PIN 10
MAF was connected to PIN 66
Same colors.
Marked everything so now I just have to find out how you relocate pins in green connector.
You get what you pay for, obviously I paid for trouble.
When I planned my project I had the ambition to modify a stock harness, some work but quality harness I figured. When I got the engine and trans I was talked into buy it with a stand alone harness, seller praised the quality. Let’s say I regret that. Already when I opened the box and looked at the ”instruction”.
PIN 57 was connected to IC 8
PIN 25 was going to a loose end in harness
IAT was connected to PIN 10
MAF was connected to PIN 66
Same colors.
Marked everything so now I just have to find out how you relocate pins in green connector.
You get what you pay for, obviously I paid for trouble.
Thread Starter
Registered User
Joined: Dec 2025
Posts: 3
Likes: 2
I retested and it was pinned out as I described. Switched pins in the PCM connector and now all MAF error codes cleared and cylinder 8 firing (I had a code on coil H as well previously).
Have noticed exhaust port on cylinder 4 and 5 is a bit colder than the rest and spark plugs on 4 and 5 not burning as nice as the rest. Will check signal wiring to coils and injectors on 4 and 5. Have eliminated coil/plug/plug wires. Maybe old be clogged injectors otherwise.
This wiring harness is a nightmare!
Have noticed exhaust port on cylinder 4 and 5 is a bit colder than the rest and spark plugs on 4 and 5 not burning as nice as the rest. Will check signal wiring to coils and injectors on 4 and 5. Have eliminated coil/plug/plug wires. Maybe old be clogged injectors otherwise.
This wiring harness is a nightmare!
