VSS and A/C idle up at PCM
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Teching In
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VSS and A/C idle up at PCM I'm most of the way through the wiring of my LS1 swap into a z32. I have it up and running but I have 2 questions one of which may be a stupid one 
Does the PCM need a speed signal to drive properly? Im using a nissan box which has a speed sensor that hooks up and works with my dash speedo perfectly but do I need to get a converter to give the PCM a speed signal.
Secondly, to get the engine to idle up when the air con is on.
Is it as simple as providing voltage to (pin 18 on red connector(A/C situation feed back)) when the air con clutch is engaged?
My low pressure switch is at the drier and uses a relay to cut power to the clutch. Will not having the low pressure sensors hooked up to the ecu be an issue?
Any help is appreciated.
Does the PCM need a speed signal to drive properly? Im using a nissan box which has a speed sensor that hooks up and works with my dash speedo perfectly but do I need to get a converter to give the PCM a speed signal.
Secondly, to get the engine to idle up when the air con is on.
Is it as simple as providing voltage to (pin 18 on red connector(A/C situation feed back)) when the air con clutch is engaged?
My low pressure switch is at the drier and uses a relay to cut power to the clutch. Will not having the low pressure sensors hooked up to the ecu be an issue?
Any help is appreciated.
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From: Monroe,NY
I have a 1999 5.3 truck pcm so you pins may be different but just hooking up the a/c request didn't work for me I had to ground pin 55 so the pcm thought the a/c had pressure. https://ls1tech.com/forums/conversio...-1999-pcm.html.
The pcm doesn't need a vss signal but I hooked mine up and it made a difference in tuning and stopped me from getting a po507 code. You are better off connecting vss signal to pcm.
The pcm doesn't need a vss signal but I hooked mine up and it made a difference in tuning and stopped me from getting a po507 code. You are better off connecting vss signal to pcm.
You may have stalling problems without a VSS signal to ecu. I was able to reproduce it on 2 builds with manual trans. I'm pretty sure it's mandatory with a 4L60, etc.
With AC, yes normally AC request ups the idle speed. That being said, I'm running a 5.3 and 6.0 (both DBW) with aftermarket AC, no AC request to ecu, and no issues.
With AC, yes normally AC request ups the idle speed. That being said, I'm running a 5.3 and 6.0 (both DBW) with aftermarket AC, no AC request to ecu, and no issues.
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PCM does not need speed signal ,,,,unless you are useing a computer controled transmission ,, in that case yes it needs it ,,, If you are useing the stock fuel injection , and a sanden ac compressor ,, i dont think you will have stall issues ,,, unless you have a cam ,,, the ac request does kick on the fan though so is needed if you are useing electric fans ,,, you need to give more info on what you have
engine
carb or injection
transmission
fan type
compressor type ,, the old pancake compresors suck up hp and will cause stalling ,,, sandens not so mutch
engine
carb or injection
transmission
fan type
compressor type ,, the old pancake compresors suck up hp and will cause stalling ,,, sandens not so mutch
Thread Starter
Teching In
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Engine is a 02 LS1 from a Holden commodore. From what I can tell its the same as and engine from an F-body.
Stock engine, fuel injection and PCM
Transmission is a Nissan GTR dogbox with PPG gears
Fans will be davies craig electric
I dont think my compressor is either of those. Mine is labeled Delphi
Stock engine, fuel injection and PCM
Transmission is a Nissan GTR dogbox with PPG gears
Fans will be davies craig electric
I dont think my compressor is either of those. Mine is labeled Delphi
TECH Regular
Joined: Oct 2011
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I dont think you will need the the vss , especialy if the nissan trany is manual ,,, you will need the ac request , hook it from you system to the computer , then to the trinary switch ,, then to the compresor ,, should work as designed ,, I have ac on all my ls swap vehicles , run like this ,,, no issues
Registered User
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I dont think you will need the the vss , especialy if the nissan trany is manual ,,, you will need the ac request , hook it from you system to the computer , then to the trinary switch ,, then to the compresor ,, should work as designed ,, I have ac on all my ls swap vehicles , run like this ,,, no issues
I have a similar issue;
I have a 2000 Camaro tune in a LS Swap Jaguar XJS.
The AC request comes in on pin 17 C2
the clutch signal comes in on pin 18 C2
The AC request shows in the scanner
no change in target idle
ac idle airflow equals zero
also, how would I get fan 2 to engage with ac request, pressure signal?
attached is the tune and the log
FYI, the log just has the wires for pin 17 testing it with and without the compressor engaged
