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Discussion Starter #1
So, I have been doing some research since I'm about to tackle the paddle shifter mod, yet I would prefer to keep my lighting in my steering wheel. I have been studying the schematic for the steering wheel for the past few weeks, and I believe I may have found a way. I noticed green wire which is located on circuit 897 which is a low reference. Now I did not know what a low reference was, so I did some research and this is my findings.

Low reference is a ground circuit but it is sourced through the PCM.


The PCM treats it to provide a “clean ground”
Normally low reference provides a ground for the electronics in the coil and the coil windings as a load device utilize chassis ground

Now if I was reading this correctly, the low reference is basically a ground wire but a cleaner version of it. So my question is. Since there is a ground wire already located inside the steering wheel, couldn't I use that ground and steal the green wire to use for my paddles? Can any electronics experts point me in the right direction? below is my idea.




 

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Good eye. Get out your multi-meter, check the resistance of the test leads first. Then check the resistancebetween the reference ground and ground in the steering wheel. Let me know what you get
 

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Discussion Starter #3
Good eye. Get out your multi-meter, check the resistance of the test leads first. Then check the resistancebetween the reference ground and ground in the steering wheel. Let me know what you get
I'm going to try this once I start the install. However, the good ol USPS broke one of my buttons on my paddles when they were shipped to me. So I have to wait for my replacement. :censored:

I am assuming as long as the ground to the steering wheel is a good ground, meaning zero or very low resistance, I should be good to use this wire.
 

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It won't be zero unless our cars are made with a superconductor.

Forgot to add....You will have to disconnect Number 5 to test this correctly.
 

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Discussion Starter #5
It won't be zero unless our cars are made with a superconductor.

Forgot to add....You will have to disconnect Number 5 to test this correctly.
What do you mean by disconnect number 5? As in clip the wire on both ends and check for low ohm? I figured I would just ensure the ground in the steering wheel had very low ohms to see how "clean" it is before I proceeded. Also, I found this. Its a GM service bulletin talking about a proper ground.

This is an old GM Technical Service Bulletin, but it should help anyone wanting to verify that their amp has a good ground:

METHOD OF VERIFYING ' GOOD ELECTRICAL SYSTEM GROUND ' #87-8-139 - (04/07/1987)
VEHICLES AFFECTED: ALL MODELS

When diagnosing electronic systems for incorrect operation, it is often necessary to verify that ground circuits are good. This article is intended to clarify what is meant by the term "good ground" and the preferred tools and methods for verifying it.

A "good ground" is a ground circuit that has a resistance of zero OHMS.

Ground circuit resistance can be measured in OHMS using a digital volt OHM meter (DVOM). When using a DVOM, it must be set on the 200 OHM scale to obtain an accurate measure of the circuit resistance. Many meters have both a 200 OHM scale and a 200 K scale. The 200 K scale will not measure zero OHMS accurately. If you are not sure how the meter is to be set for the 200 OHM scale, refer to the meter operating instructions for proper settings. If the meter is an autoranging or self-scaling meter, read the meter carefully to be sure which scale it is setting itself to.

Before measuring resistance in any circuit, the resistance of the meter should be measured by touching the leads together. A meter with a good battery and leads in good condition will read less than .2 OHMS usually zero. If the leads measure anything more, an accurate measure of the circuit resistance may not be possible.

Always remember - resistance cannot be measured accurately on a "live" circuit, All current flow through a circuit must be stopped by disconnecting its power source before measuring resistance.

Ground circuit resistance can also be checked by measuring the voltage drop across the circuit with a DVOM set on, the 2 volt scale. The voltage drop will be zero across a "good ground" circuit.

Remember, fully understand a meter's functions before using it!
To add to this, a good ground for car audio applications will have a return resistance reading of 1/2 ohm or less. I have yet to have a return reading of 0 ohms. If a ground return reading cannot be made to get below 1/2 ohm by means of the "BIG 3", then it is adviseable to ground direct to the battery. Electricity is an algebra equation, what you do to one side you must do to the other. Pay as much attention to the ground wire as you do the power wire.
The BIG 3 is a great place to start for a good ground, however it is the assumed proper method of grounding. What we are talking about here is the older and wiser 4th brother to the BIG 3 (the BIG 4).
So a proper ground wire will be as follows.
- clean of residue and paint.
- secure.
- have a resistance return of 1/2 ohm or less.
- be of adequate guage to carry the return as compared to the power wire.
To simplify the measuring of the return, use your meter as described. Disconnect the - battery terminal and disconnect the ground wire from you amp. If your dmm probes are not long enough, you will need to create a jumper extension out of some primary wire or whatever wire you have handy. Measure this wire for any resistance reading and subtract it from the total.
Many installers are not aware of this nor practice this method. It takes time and time = $ so don't get all pissy if you had a professional install done and this was not checked. A poor ground connection or high resistance reading may seem trivial under no load, but once you are pounding your nice new amp and it is drawing large amounts of current, this little reading has become a monster reading that has caused many an amp to fail for no apparent reason. It may be noticeable as a extremely hot running amplifier in a short time period, poor output levels or diminishing levels and of course a blown power supply or output section in the amplifier.
While the original article was written for the years gone by, it still is applicable to the newer generation of vehicles. A good ground is not about the amount or size of the metal in the return to the battery but about the resistance through it. Todays vehicles are a combination of metals, spot welds, glued together unibody panels and isolated chassis components. The return through these components is where the resistance reading comes into question and this is what we need people to understand, why the BIG 4 needs to be done if the BIG 3 does not solve the problem.
 

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Wait...You're right..duh. My bad
 

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Discussion Starter #7
Wait...You're right..duh. My bad
Don't feel bad bro. I'm just glad someone decided to discuss this topic with me. Hell it's been 11 years since I've taken an electronics course. I very much open to suggestions. So yeah, I plan to check the ohms at the ground in the steering wheel. Unless I'm missing something and I can't use that ground. I wonder why the low reference goes into the instrument cluster??


Sent from AutoGuide.com App
 

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The Instrument Cluster senses the resistance as you press a switch and the local ground ensures it reads the desired resistance accurately. A non local ground could cause erratic readings.
 

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Discussion Starter #9
The Instrument Cluster senses the resistance as you press a switch and the local ground ensures it reads the desired resistance accurately. A non local ground could cause erratic readings.
Would you be able to expand on "local ground?" If the ground at the steering wheel is as "clean" as a ground as the one in the instrument cluster, would it even matter if I used either one?
 

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Discussion Starter #11
It may read the wrong function when you press a button, but its worth a try.
I guess it doesn't hurt to try. If all else fails, I can return it to normal. I just hope in the case it does read a bad resistance, It doesn't burn out the BCM. That would not be cool!
 

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local ground refers to the fact that the sense wire(far left on your diagram) is reading a closure to ground as you press each switch, showing it a different 'resistance to ground'. If that ground isn't local to where the sense is, it can't read the resistance accurately.
 

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It could see the other ground as a small resistance and think you are pressing a button all the time or it could be fine. I'd try it.
 

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Discussion Starter #14
local ground refers to the fact that the sense wire(far left on your diagram) is reading a closure to ground as you press each switch, showing it a different 'resistance to ground'. If that ground isn't local to where the sense is, it can't read the resistance accurately.
I see what your saying. I think I may be okay since the wire you are talking about "orange/black" comes from the BCM. The low reference wire I'm wanting to use is at the instrument cluster. It wont hurt to try it. I'll post my results once I get this done in a few weeks.
 

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Discussion Starter #15
What are the chances I might be able to leave the airbag and fuse off the car. Hook up the wires, then connect the battery to see if it works. Or would that cause me to trip codes?
 

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When you press these buttons it adds a resistor to the circuit. Since each button uses a different resistor value, the computer senses a different voltage for each button, Ohms law. The computer senses this voltage with reference to ground.(example: 1 volt do this, 2 volts do that, 3 volts do both, etc) If there is any resistance between the reference ground and the steering wheel the computer will sense a different voltage than what it's looking for. Depending on the tolerance, it could work.
 

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Discussion Starter #17
When you press these buttons it adds a resistor to the circuit. Since each button uses a different resistor value, the computer senses a different voltage for each button, Ohms law. The computer senses this voltage with reference to ground.(example: 1 volt do this, 2 volts do that, 3 volts do both, etc) If there is any resistance between the reference ground and the steering wheel the computer will sense a different voltage than what it's looking for. Depending on the tolerance, it could work.
Yeah I was going to say, won't it depend on what the tolerance is in the circuit? I see what you mean now though. How pushing for example the Onstar button sends a voltage signal to the BCM. Of course the resistors wired inside the wheel controls reduce the voltage to give the proper signal for the component. If you disrupt this with a ground that is not "clean" then you can throw the resistance value off, causing said component not to send the proper voltage signal. I can only hope the ground inside the wheel is clean!
 

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Should probly check the resistance while turning the wheel back and forth since you will be shifting at different degrees of steering.
 

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Discussion Starter #19
Should probly check the resistance while turning the wheel back and forth since you will be shifting at different degrees of steering.

I agree. Need to ensure no stone is left unturned. In the event this is possible, that would be awesome!
 

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Discussion Starter #20
I just found this in the service manual. This doesn't look promising.

The instrument panel cluster (IPC) supplies a regulated voltage supply to the steering wheel control switches and monitors the return signal. Each switch state is associated with a specific resistance value. When a switch is depressed a specific voltage drop occurs across the resistor unique to that switch. The IPC is able to identify which switch was depressed by recognising the voltage drop associated with that switch and responds to the selected request.

I wonder which side the IPC identifies the voltage drop from. The power side or Orange/Black wire, or the ground side or green wire.
 
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