relentlesshustler

I'm looking to run a toggle switch for "high idle" that will tell the PCM that the A/C is on(not currently running A/C). I have read that it will not work without pressure sensors and I've also read that it may be possible to wire up resistors but the instructions were unclear. I have an LQ4, harness, and underhood fuse block from a 2003 Chevrolet Express. Donor vehicle is a Square Body car carrier. I understand I'm not inventing the wheel here and a link to the answer would be greatly appreciated!!

Eric

G Atsma

The donor vehicle was the Chevy Express van, as it donated the engine. The carrier is the recipient vehicle or swap vehicle. Just thought you would want to know.

relentlesshustler

In my world the donor vehicle is what's getting the LS Swap. Thanks for being a grammar **** and not answering my question.

G Atsma

Welcome to the REST of the world.... lol

LLLosingit

iTrader: (4)

If it's a cable driven throttle then why not just use the correct setup. Heavy Duty Automatic Cable Throttle Control System

LLLosingit

iTrader: (4)

Not to add to the argument but a heart donor dies and the heart goes into the recipient lol

ChopperDoc

I found this for you... I know what you are trying to do, and it makes sense so long as you can change all the affected tables to compensate for PTO operation. It really comes down to supplying the correct voltages to the right pins on the PCM. 12v for the compressor, which is grounded to turn it on, through a relay, and 5v reference signals from the pressure sensors. I'm going through this guide to further understand it myself. Basically you have to trick the PCM to thinking A/C is on and stays on.

https://www.lsenginediy.com/upgradin...tioning-guide/

ChopperDoc

I don't know what PCM you have exactly, but if you have a schematic it would be highly useful. It would appear that supplying 12v to pin 17 through a relay and putting in 80k ohm 1/4 watt resistors on the pressure signals will fool it. I might be reading that wrong, it's early where I am, but pin 17 is the "on/off" basically, provided the PCM is the 98-02 Camaro/firebird PCM. Since it's an 03, this may be different on yours which is why I would definitely get the pinout/schematic for your particular PCM before proceeding here. There's probably more too it, but as I read it, the only thing left would be the actual compressor output from the PCM to deal with, since it grounds that signal to activate the clutch, but also monitors the voltage while it's on. Gotta love this stuff. If it were easy everyone would be doing it lol.

Hopefully someone more familiar with electricity and inputs/outputs can further elaborate here on the basic concept based on that article, which I found very helpful in understanding this system and how it works.

aknovaman

iTrader: (7)

Why make it more complex than needed? i found the easiest way is to wire in a park neutral (toggle) switch to the PCM input and tune your commanded idle sped (PTO speed) based upon if you are in park or neutral. No other parts are needed.

relentlesshustler

$350?

relentlesshustler

@LLLosingit - I don't want to spend $350 and still have to wire a relay. I paid $2200 to unlock HP Tuners so I can figure out the easiest/cheapest ways to do certain things that can be duplicated in the future.

@ChopperDoc I'm unsure on the model number of the PCM but it's from the "donor" 2003 Chevrolet Express. You're exactly on the right track on what I'm trying to do. I briefly looked at that website but will further dive in when I have the time. Thank you for that!

@aknovaman Can you provide a part number for the park/neutral toggle switch you are referring to and where exactly in HP Tuners I can change the commanded idle speed for when the switch closes the circuit? FYI: I want to normally idle at 600rpm and 1800rpm for high idle for PTO operation

Thank you all for your time. I've searched high and low for the answer with no black and white answers, just hypotheticals. Hopefully if we can put our heads together and help people in the future that are crazy enough to put a standalone Vortec/LS Engine in something that has hydraulics/PTO. Who knows what people in 10-50 years will be doing with these motors ?

relentlesshustler

@ChopperDoc Post #75 has the schematics for a 2004 Chevrolet Express 6.0L https://ls1tech.com/forums/conversio...ml#post7775112

ChopperDoc

The schematics aren't completely helpful. I found the wire in question, and it is in fact numbers 17, but it is a different color than the actual pin 17 coming from the PCM. Can you provide the part number from your PCM? Picture of the sticker? It's the easiest, and most accurate way to do this.

Note: I've had a few, so trying to read these things right now is tough lol.

pdxmotorhead

Isn't the factory AC rpm < 1000?
Is the A/C on idle set point configurable? I'd assume so,, but haven't looked..
If its a cable throttle that would be easy,, just add a run-up cable from Wicks or aircraft spruce to the throttle body..

aknovaman

iTrader: (7)

Will you be needing the idle to be raise in only park and not when in drive? if so then just raise the park commanded idle speed up to where you want it to be. The internal trans switches will tell the PCM that you are in park. If you want to actually select when it raises the idle, then use the AC ON table settings and you will need to set the "AC type" settings. I forget what they need to be but eric wise describes them in his conversions thread.

https://ls1tech.com/forums/conversio...bed-build.html

relentlesshustler

@ChopperDoc 2003: Serv. No. 12576106 with Hwd. No. 12570558

@pdxmotorhead If I wanted to run a cable to the throttle body I would run the choke cable that's already there. I want to figure out how to trick the PCM into thinking the A/C is on and changing the parameters to 1800RPM. The possibilities for this engine to run hydraulics at the perfect RPM with the flick of a toggle switch everytime without a cable is what I'm after, respectfully.

@aknovaman The transmission is a manual 4 speed SM465 and to my knowledge doesn't have switches. I need the high idle in NEUTRAL, there is no park. And why would I need high idle while "in drive"?

I'm actually surprised no one has the answer.... I thought for sure everything has been ironed out by now. Maybe this is a questions for the HP Tuners forum seeing how it's more of a programming situation ? Any help pointing me in the right direction is much appreciated.

Eric

aknovaman

iTrader: (7)

Go here for a diagram showing another option.

http://www.chevythunder.com/1999x%20...0PNP%20sw..gif

One of the 4 wires from the PN switch tells the PCM that you are in park. I forget which it is. Grounding it will raise your idle. Update the park idle settings in the file and in turn ground each of the 4 inputs to determine which raises your idle. That should solve your problem.

relentlesshustler

@aknovaman That sounds crazy enough to work! I hope to have some time tomorrow to tinker with the old girl. I'll be in touch. Tyvm!

kpeters59

It sounds like you've got the 0411 ECM. It should have a sticker.

I just spent a bunch of time getting my A/C turned back on.

Pin 17 is A/C Request.

Pin 55 is the Low Pressure Switch. I grounded mine.

Pin 11 is the High Pressure Switch. Apparently you can use a resistor to 'trick' the ECM in to thinking the High Pressure is Hunky-Dory.

I suppose then you'd Tune for High A/C Idle and a Toggle Switch to simulate A/C Request. Or maybe the PTO supplies the switch?

HTH.

-KP

relentlesshustler

Thank you @aknovaman I'm halfway there! I ran one side of a toggle switch to ground and the other to pin #34 on the blue connector. It's changing from D4 to Park correctly but for some reason the "Idle Desired RPM" is showing 1200RPM and not the 1800RPM that I set the "Base Setpoint" parameters too. I also changed to "P/N only". I tried to change the idle to 1800rpm in both the "in gear" AND "park/neutral" thinking maybe the pcm won't idle that high in "park/neutral" but the pcm is still showing 1200rpm as the desired idle

Thoughts? Did I set a critical component to "error not reported" in the engine diag? Is it because I'm not running an A/C or VSS at the moment that the pcm won't idle higher? Is a van OS default at maximum idle of 1200rpm and maybe I should re-flash a different OS and segment swap?

Any help would be greatly appreciated !!