ECM outputs - hot or grounds?
03-17-2006, 02:43 PM
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ECM outputs - hot or grounds? Howdy,
I've had some confusion on this. Does the ecm output to the MIL light, Fan & Fuel Pump relays a positive voltage or a ground? Also, does anyone have a wiring diagram of the AC clutch relay? I'm about to try starting up my swap and wanted to double check.
Thanks
James
I've had some confusion on this. Does the ecm output to the MIL light, Fan & Fuel Pump relays a positive voltage or a ground? Also, does anyone have a wiring diagram of the AC clutch relay? I'm about to try starting up my swap and wanted to double check.
Thanks
James
03-17-2006, 05:29 PM
#2
TECH Resident
The MIL and Fan signals are grounds. The F.P. is a pos. 12V out from the ECM.
Don't have any thing ot offer on the A/C relay, I'm sure someone will chime in with help though.
Don't have any thing ot offer on the A/C relay, I'm sure someone will chime in with help though.
03-18-2006, 01:27 PM
#3
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Charles O. Probst book entitled "how to understand, service and modify Corvette Fuel Injection and electronic engine management" should give you the info you need.
It has wiring diags/schematics for a 98-01 LS1.
It has wiring diags/schematics for a 98-01 LS1.
03-18-2006, 06:29 PM
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LS1 or truck motor?
I'm positive that my Mal light for the truck harness gives a positive signal. The other leed off the LED goes to a ground it works fine.
-Matt
I'm positive that my Mal light for the truck harness gives a positive signal. The other leed off the LED goes to a ground it works fine.
-Matt
bump for more input
03-26-2006, 03:18 PM
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04-04-2006, 11:56 AM
#8
I have a '98 Z28 engine in my RX7. The fuel pump enable is 12 V. ALL other control signals are active low (ground).
Let me qualify the above. I am refering to all PCU control signals interfacing with the body harness.
Let me qualify the above. I am refering to all PCU control signals interfacing with the body harness.
Last edited by RFERG43; 04-04-2006 at 12:31 PM. Reason: Mor info
04-04-2006, 12:53 PM
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Thanks for the help guys, the fuel pump is 12v signal from the 98 pcm, and fans are ground signaled from pcm, the MIL light is ground signaled as well - just like you guys said 
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
04-04-2006, 01:46 PM
#10
Originally Posted by z28evans
Thanks for the help guys, the fuel pump is 12v signal from the 98 pcm, and fans are ground signaled from pcm, the MIL light is ground signaled as well - just like you guys said
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
pay $1000 for a GM service manual, and trace it down with our fingers... lol
04-04-2006, 04:07 PM
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Originally Posted by z28evans
Thanks for the help guys, the fuel pump is 12v signal from the 98 pcm, and fans are ground signaled from pcm, the MIL light is ground signaled as well - just like you guys said
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
Spenser309 - thanks for the link to the wiring diagrams, got my A/C questions answered.
What would we do without forums?
-Matt
04-04-2006, 05:03 PM
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The MIL light is a ground and a B+ feed. One side of the light is feed B+ and the other side is also B+. When a code is tripped, it will set the MIL function and turn the one B+ into a ground therfore illuminating the MIL light. It cannot set when there is B+ on both sides. Naturally it is a B+ and will set to a ground when the MIL is demanded. AS everyone stated before they are all switched grounds besides the FP relay output. Hope that helps.
-Alex
-Alex
thanks that seems to clear things up. they should include this in the wiring sticky.
04-04-2006, 09:31 PM
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Originally Posted by Slo_240sx
The MIL light is a ground and a B+ feed. One side of the light is feed B+ and the other side is also B+. When a code is tripped, it will set the MIL function and turn the one B+ into a ground therfore illuminating the MIL light. It cannot set when there is B+ on both sides. Naturally it is a B+ and will set to a ground when the MIL is demanded. AS everyone stated before they are all switched grounds besides the FP relay output. Hope that helps.
-Alex
-Alex
-Matt
02-26-2008, 08:28 PM
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I'm confused... I've got brown/white wire from PCM to ground side of light. Other side of light to 12V power. MIL light no worky. Should I have the other side of the MIL light to ground?
02-26-2008, 08:58 PM
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Yeah, I actually wired it (for testing purposes) to a constant 12V feed and still it didn't light up. I've read that some people have the other side of the LED (on truck engines) wire to ground. Might this be my problem?
