94-95 & 96-97 MAF Delete Discussion
11-20-2007, 01:13 PM
#22
sam, according to diy installation thats why i did pins 3&4 for the IAT
http://megasquirtpnp.com/models/mm94...495_manual.htm
look half way down the page...
http://megasquirtpnp.com/models/mm94...495_manual.htm
look half way down the page...
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11-20-2007, 01:37 PM
#23
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use you pins 3 & 4 because 3 is the sensor ground, and 4 is the output to the ECU. So should build your harness to pick up the AIT sensor signal off the factory harness. Make wiring extremely simple/easy....
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11-20-2007, 02:54 PM
#25
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I'm not... I think I need a diagram.
The problem I see here is that there is only one signal line (4).
1) Chassis Ground (SHARED)
2) Sensor Ground (SHARED)
3) 5V (SHARED)
4) Red/Wh = Signal
5) 12V (SHARED)
So, the ecu can't measure resistance/current change on the heater or it can't measure AIT. Unless both signals are being kicked out on the same line, like say in a PWM. This is the issue I'm having. The ONLY line not shared (per the schematic) is pin 4. One wire = one signal. WTF?
The problem I see here is that there is only one signal line (4).
1) Chassis Ground (SHARED)
2) Sensor Ground (SHARED)
3) 5V (SHARED)
4) Red/Wh = Signal
5) 12V (SHARED)
So, the ecu can't measure resistance/current change on the heater or it can't measure AIT. Unless both signals are being kicked out on the same line, like say in a PWM. This is the issue I'm having. The ONLY line not shared (per the schematic) is pin 4. One wire = one signal. WTF?
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11-20-2007, 03:35 PM
#27
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#3 is the intake sensor....it shouldn't be a shared signal. it's simply the input for the ECU to read the AIT from.
Take voltmeter from the #3 pin on the harness and (94-95 2P Red/Black) (96-97 3K Red/Black) and you'll have no resistance. it goes straight from the harness to the ECU.
Since the MAF only has two functions, temp and airflow, you can easily assume the red/green wire is the MAF signal. Black/Blue & Black/Lt Green are always grounds, all years. White/Red is always +12v, all years.
Take voltmeter from the #3 pin on the harness and (94-95 2P Red/Black) (96-97 3K Red/Black) and you'll have no resistance. it goes straight from the harness to the ECU.
Since the MAF only has two functions, temp and airflow, you can easily assume the red/green wire is the MAF signal. Black/Blue & Black/Lt Green are always grounds, all years. White/Red is always +12v, all years.
Last edited by Braineack; 11-20-2007 at 07:13 PM.
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11-20-2007, 05:28 PM
#29
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#4 is the intake sensor....it shouldn't be a shared signal. it's simply the input for the ECU to read the AIT from.
Take voltmeter from the #4 pin on the harness and (94-95 2P Red/Black) (96-97 3K Red/Black) and you'll have no resistance. it goes straight from the harness to the ECU.
Since the MAF only has two functions, temp and airflow, you can easily assume the red/green wire is the MAF signal. Black/Blue & Black/Lt Green are always grounds, all years. White/Red is always +12v, all years.
Take voltmeter from the #4 pin on the harness and (94-95 2P Red/Black) (96-97 3K Red/Black) and you'll have no resistance. it goes straight from the harness to the ECU.
Since the MAF only has two functions, temp and airflow, you can easily assume the red/green wire is the MAF signal. Black/Blue & Black/Lt Green are always grounds, all years. White/Red is always +12v, all years.
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11-20-2007, 07:12 PM
#30
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well, you'd be smart to wire your GM AIT sensor directly through the MAF harness....that way you kill two birds with one stone, the ecc sees it and is happy and MS sees it and is happy.
the MAF signal is a guess, but an educated guess. I assume as long as the ecu sees something between 0-5v it won't throw a code.
the MAF signal is a guess, but an educated guess. I assume as long as the ecu sees something between 0-5v it won't throw a code.
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11-20-2007, 07:37 PM
#31
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well, you'd be smart to wire your GM AIT sensor directly through the MAF harness....that way you kill two birds with one stone, the ecc sees it and is happy and MS sees it and is happy.
the MAF signal is a guess, but an educated guess. I assume as long as the ecu sees something between 0-5v it won't throw a code.
the MAF signal is a guess, but an educated guess. I assume as long as the ecu sees something between 0-5v it won't throw a code.
why would it be any smarter to wire in the GM AIT instead of a static resistor? it's not like the stock ECU is going to know what is going on anyways since the GM and stock sensors have difference resistance curves.
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11-20-2007, 10:43 PM
#34
I ran my AIT back through one of the wires in the A/C harness (there's 3 wires that go back to the ECU if I remember correctly). And the harness is right there next to the TB in the 94. But I don't have A/C. It made a nice alternative to running a wire across the engine bay to the MAF connector, or running a completely separate wire.
I'm running standalone, so I can't offer any wisdom on the CEL issue.
-Mike
I'm running standalone, so I can't offer any wisdom on the CEL issue.
-Mike
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11-21-2007, 08:55 AM
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11-21-2007, 10:27 AM
#37
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Sam I'd get it running with the MAF attached and share the factory sensor. Make sure as is kosher and no CELs as is. Go ahead and get the GM sensor installed where you want it, but leave it disconnected.
then when you are confident everything is good, remove the afm and wire the sensor up into the harness, then try the resistor. Not sure what size you'd want, something to drop 12v to 4v.
then when you are confident everything is good, remove the afm and wire the sensor up into the harness, then try the resistor. Not sure what size you'd want, something to drop 12v to 4v.
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11-21-2007, 11:08 AM
#40
The wiring doesnt make sense.
The AIT gets wired into 5v, and signal. Whats left? Sensor Ground, 12v, and Chassis ground. I cant wire in 12V + resistor into the Signal, I am no electrician but that doesnt sound right.
Last edited by Saml01; 11-21-2007 at 11:28 AM.
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