2006 truck LQ9 (gen3) with a 4L65E in a 90 Jeep YJ.

I want to install a Vernier throttle, to raise my RPMS manually when in neutral, or 4 low. This would mainly be used just for bumping up the RPMS when using an onboard welder or onboard air. It could also be used as a very slow speed cruise control when wheeling. Big trucks use cable Vernier hand throttles for this purpose when running a PTO or whatnot.

Since I have DBW, I am wondering if anyone has figured out how to do this electronically? I technically could do the cable setup to my gas pedal, but having a switch and a potentiometer would be a much more elegant solution. Has anyone done something similar?

 

I would say an adjustable stick from the front of the seat to the throttle pedal.

 

if you're not using it for air conditioning, could you use the a/c request input to raise the rpm? in know 03 up uses can bus but i believe there is a workaround to use an analog signal like the earlier (99-02) pcms

 

Hmmm. I can think of a couple of ways, but safety is potentially compromised whenever you raise the throttle artificially. Having said that, here are some possible ideas that you might consider.

1) Instead of having the pedal use the hard stop on the way up, you might install a screw adjustable stop so when the pedal comes back up, it doesn't come back up all the way.
2) Add an external idle solenoid, past the throttle plate to let more air into the4 intake.
3) switch in 2 extra resistors in series with the potentiometers in the pedal assembly to fool the ECM/BCM into thinking you have the pedal pressed down somewhat.

Actually I do #3 in my vette, but in reverse. I fool the computer into thinking I have less throttle than I actually have (for boost control).

 

I'm not sure if you were joking, but that is actually what I do now! lol

That is a solid thought for sure, as long as I can control the RPM's, and not just bump to a single value

#3 is what I am leaning towards. I would have to have the switching setup on a relay for safety. I push a momentary switch, the relay latches, and I now feed in my artificial input in place of the pedal input. I'd have it so that touching the brake pedal would unlatch the relay, so things can't get crazy if I use this while wheeling.

I have a background in electronics, so I believe I can make this work.

***EDIT: I just finished reading through your c3 project. I am nowhere near your league when it comes to electronics. Amazing stuff. But I still believe I can accomplish what I need lol***

 

So I did some poking around the inputs/output of my pedal and I have found a few things. There are only 6 wires going to 2 potentiometers. Each has a High reference (4.7V), a low reference (0V) and a signal, which is fed to the PCM. Both Signals read roughly 0.8v with 0% throttle, and 4.0V with 100% throttle. As long as these two values agree, the PCM commands the throttle body to open/close in turn.

The odd part is that these 2 pots do not read with an Ohmmeter how I would expect. Reading across the Hi and Lo reference legs, I read 1.67k on each one. Reading between the wiper (signal) and the Lo leg gives me 1.34k. Between the wiper and Hi shows 2.36k. This with 0% throttle. If this were a traditional pot, I should have 1.67k in total after adding the two values.

Am I missing something simple here? Maybe it doesn't even really matter.

Anyways, it looks like I need to come up with a combination of resistors to go with a pot to allow 0.8V min and 1.25V max at the dial extremes. I can buy a stacked potentiometer, so both are turned at once. The 1.25V equates to 10% throttle pedal, and 2000rpms which is higher than I need, but should be a safe top limit for this. I'm basically just laying out the info here for others to see, and maybe yell at me if I am way off base.

 

You're on the right track. My 2002 pedal pots did ohm out as you would expect. Don't know what's going on in yours. You need the diagram for the pedal to make sure you got the pins right.

 

Possible method number 4. Not as adjustable, but I'm throwing it out there anyway.....
4) add a diode in series with App1 signal wire and also App2 signal wire. Scottky diodes reduce the voltage by .3v. You could have multiple diodes in series if you need a different RPM. Shunt across the diode(s) with a switch to run in normal mode. The more diodes are not shunted, the higher the RPM.


I'm assuming you're aware that on one of the signal wires, the voltage goes from 0 to 5 as you press the pedal and on the other one it goes from 5 to 0 as you press the pedal. Also, the voltage has to be in the right range, but opposite range on both, or it may go into limp mode thinking there is a pedal problem.

 

I believe that is only correct from 1999 to 2002. From my source (https://www.lsenginediy.com/gm-gen-i...uipment-guide/) it shows 2006-2007 should be matched 0-5V. I confirmed this by back probing the signal wires to the TAC module from the pedal assy and depressing the pedal with the key in run, but the engine off. The 0.8 - 4.0V is also shown on my obd2 reader under live data APP1 & APP2.

The diagram I posted shows the pedal, and all the pinouts match up, so I think I have this just about figured out. My real issue right now is how to output 0.8 to 1.25V from 5V.

Thanks for your thoughts on this, I truly do appreciate your input.

 

Possible method number 5. I'm liking this one the best so far. Full adjustability, safest, easiest ....
5) instead of having the resistances in series, just use your stacked pot to emulate a second pedal and switch the wiper signal between the real pedal and your stacked pot. That way your your stacked pot resistance does not have to be exactly matched to your pedal pot. You would have a single fixed resistor on each end of the pot to limit the maximum safe throttle your pot could add.

I don't think switching back and forth quickly, will upset the ECM.

I can draw a diagram but I suspect you'd like to come up with it on your own.

Amazing how a cup of coffee helps you think outside the box.

 

Ok, we are on the same page now, lol! Yes this is what I was suggesting before, but I guess I did not convey it that well. I welcome a diagram, because I am having trouble figuring out how to setup a voltage divider & potentiometer to get the voltages I need.

Cheers.

 

Did not know it changed in 2003. Good stuff!

 

The simple solution is to switch it to a DBW setup. Different ECM, different throttle body, different pedal, some tuning, and you're in business.

If you do the relay switching from a foot throttle to a hand throttle, use an accelerator pedal as the hand throttle. That will give you the correct sensor, and you just need to fab up a handle and a friction mechanism to hold it in place. Don't do all the fab work until you know if the concept is valid or not. Simply wire two foot throttles together with the necessary relays to switch between them. Confirm the ECM can handle this without problem before you convert the one into a hand throttle.

If you're wondering if your pinout is correct, some accelerator pedal sensors can be opened up. My 2010 Tahoe pedal opens with a couple of screws, and you can see the wiper and the contacts.