I was suspecting these shifter paddles communicate over CANbus, as almost all components do these days (even the tail lights!) but your Oscilloscope seems to disagree. (I can't verify thou, because I don't know what bandwidth that scope runs at - maybe it isn't good enough to see fast digital comms). I don't know WTH is going on with this but what I do know, is that just about every button and every function on these cars nowdays communicates over CANbus and there is some information generated when you do anything.

For example, in my 2005 GMC Sierra, when I do something as simple as press any of the buttons the steering wheel (EX: "volume UP"), I would see a CANbus message come across with my sniffer. Now the button itself probably didn't generate the CANbus signal; it was probably just a digital input to some module somewhere, but that module generated a message I was able to see.

I don't know what it is you're trying to do, and I don't understand the measurements you're getting or how the paddle shifter works, but I can give you a guaranteed way to detect if the paddle shifter has been pressed: CANbus. You can either use that sniffer I linked to, or if you're trying to embed something in the car you could probably use an arduino with a CANbus shield. The arduino monitors the CANbus and activates an output when it sees the message from the paddle shifter.

If you don't have any circuit-building experience, this would probably actually be easier than building a custom circuit to interface with the paddle shifter signals.

 

I was suspecting these shifter paddles communicate over CANbus, as almost all components do these days (even the tail lights!) but your Oscilloscope seems to disagree. (I can't verify thou, because I don't know what bandwidth that scope runs at - maybe it isn't good enough to see fast digital comms). I don't know WTH is going on with this but what I do know, is that just about every button and every function on these cars nowdays communicates over CANbus and there is some information generated when you do anything.

For example, in my 2005 GMC Sierra, when I do something as simple as press any of the buttons the steering wheel (EX: "volume UP"), I would see a CANbus message come across with my sniffer. Now the button itself probably didn't generate the CANbus signal; it was probably just a digital input to some module somewhere, but that module generated a message I was able to see.

I don't know what it is you're trying to do, and I don't understand the measurements you're getting or how the paddle shifter works, but I can give you a guaranteed way to detect if the paddle shifter has been pressed: CANbus. You can either use that sniffer I linked to, or if you're trying to embed something in the car you could probably use an arduino with a CANbus shield. The arduino monitors the CANbus and activates an output when it sees the message from the paddle shifter.

If you don't have any circuit-building experience, this would probably actually be easier than building a custom circuit to interface with the paddle shifter signals.

This seems to be the schematic for a transmission similar to mine. Thoughts?

 

This seems to be the schematic for a transmission similar to mine. Thoughts?

Thoughts:
1. Why the HELL is this going through the airbag circuit?
2. No way I would tamper with that at all.

I would go with CANbus. Maybe someone else understands this better than I do, and isn't scared to play around with the airbag. That's not me.

 

Thoughts:
1. Why the HELL is this going through the airbag circuit?
2. No way I would tamper with that at all.

I would go with CANbus. Maybe someone else understands this better than I do, and isn't scared to play around with the airbag. That's not me.

I think that diagram is misleading. Its the steering wheel module that the airbag and steering controls pass through. From what I read, the BCM (body control module) has to be flashed to used the factory setup. I just have the buttons and want to go around doing that.

 

I think that diagram is misleading. Its the steering wheel module that the airbag and steering controls pass through. From what I read, the BCM (body control module) has to be flashed to used the factory setup. I just have the buttons and want to go around doing that.

Misleading? The drawing leaves no room for misinterpretation. It clearly shows the control signal going directly through the airbag coil, and is labeled as such. If that's not true, then the drawing is just plain wrong.


Edit: never mind. I googled it. The coil is just a flexible conductor that they use to trnsfer the stationary wires to the rotating wheel, instead of a slip ring.

 

What exactly are you trying to do here?

 

What exactly are you trying to do here?

I’m under the impression that since there is no PWM, that I can tap into the existing shifter wires and simulate the shifter TU/TD (tap up/tap down) with the paddle switches. The switches themselves have resistors built in but they are the incorrect resistance to achieve what I’m looking for. The resistors that are in them are for BCM enabled vehicles. IF the transmission signal IS canbus, would it still have those resistors?

 

I’m under the impression that since there is no PWM, that I can tap into the existing shifter wires and simulate the shifter TU/TD (tap up/tap down) with the paddle switches. The switches themselves have resistors built in but they are the incorrect resistance to achieve what I’m looking for. The resistors that are in them are for BCM enabled vehicles. IF the transmission signal IS canbus, would it still have those resistors?

Canbus are square wave signals. You should have canbus high and canbus low circuits. Total voltage between high and low is 3.75 volts. You cannot have correct canbus signals if voltage total doesn't equal 3.75 volts.

 

https://www.linkedin.com/pulse/automotive-can-bus-system-explained-kiril-mucevski?osm=1
Check this out.

 

I’m under the impression that since there is no PWM, that I can tap into the existing shifter wires and simulate the shifter TU/TD (tap up/tap down) with the paddle switches. The switches themselves have resistors built in but they are the incorrect resistance to achieve what I’m looking for. The resistors that are in them are for BCM enabled vehicles. IF the transmission signal IS canbus, would it still have those resistors?

Man I really am not following you. Are you trying to install paddle shifters in a vehicle that didn't originally have them?

There is no canbus at the switches from what I can tell. The module that the switches interface with, probably measures the current to identify the resistor to identify the switch, and then turns that into CANbus. Or maybe those wires go all the way to the transmission but I doubt it,

 

Man I really am not following you. Are you trying to install paddle shifters in a vehicle that didn't originally have them?

There is no canbus at the switches from what I can tell. The module that the switches interface with, probably measures the current to identify the resistor to identify the switch, and then turns that into CANbus. Or maybe those wires go all the way to the transmission but I doubt it,

Right, my car did not have them, I want to install them without having the dealership flash the BCM/TCM. If there is no CANBUS since I am not reading any square waves, I should be able to do a drop resistor but like I said before, how do I account for the voltage fluctuations from 12VDC to 14.5VDC when I’m doing my resistor calculations?

 

Right, my car did not have them, I want to install them without having the dealership flash the BCM/TCM. If there is no CANBUS since I am not reading any square waves, I should be able to do a drop resistor but like I said before, how do I account for the voltage fluctuations from 12VDC to 14.5VDC when I’m doing my resistor calculations?

OK thanks for the clarification. I don't know what you're going to do with those signals though. is there an input somewhere?

As far as the voltage fluctuations go, I doubt it will matter. The module that the switches interface with is probably looking for a certain current, no so much a voltage. They likely do it this way using a current signal so that it is less susceptible to noise. The module probably has a very low input resistance.

@12V:
Down: 8mA
Up: 2.7mA
none: 1.4mA

@14.5V:
Down: 9.6mA
Up: 3.2mA
none: 1.75mA

So if we express as a range:
Down: 8.0 - 9.6mA
Up: 2.7 - 3.2mA
none: 1.4 - 1.75mA

So there is sufficient gap between the ranges to prevent the module mis-reading. However I'm surprised at their choice of resistor values. They put the "Up" value uncomfortably close to the "none" value for my taste. I would have put a 2.2kohm for 5.4mA, right in the middle.

Can you explain where you're taking these signals (what module) and what kind of input the module is expecting? Does it already have inputs for this? and if so, why aren't you using them?

 

Is there by chance a way to solder a connection to the switch itself? Instead of trying to recreate the circuit, just parallel the switches (maybe...)

Do you by chance have a schematic of the shifter itself? Sometimes a Haynes manual (or whatever shop type manual you have access to) has little pieces of info about odd stuff like this... sometimes they don't. I've tried to dig around online a bit, but came up empty so far.

Have you measured the resistance of the shifter itself to test how the switches work? Since you have an idea of what's happening so far maybe a little poking of the shifter connector when it's disconnected will shed some more light.

Strantor may be on to something with the current sensing and if so you may be better off with the parallel switches if it will work.

 

I also just realized while going back to look through this for details you mention stepping down the 12 volt for your paddles. You're going to want to tap into a 5 volt source somewhere to use instead.

Long story short your voltage is never 12 or 14 volts or whatever your gauge says. It could be upwards of 100 volts for instant, but not hurt anything since it's designed to handle it. Normally an ECU input has some level of protection, but it's not intended to be hacked and added on to so it's possible you will fry either the input or the ECU itself in the event of a voltage spike.

 

I also just noticed the schematic you linked above. I would guess it's probably pretty close to yours if not the same. Same internals, different cover, and maybe a couple less wires since it seems to show a secondary paddle. I'm thinking your safest bet is going to be to parallel the switches.

 

So I dug around the shifter assy. The electrical harness I am tapping into goes to the micro switches located in the shifter path. The harness I am tapped into is PRE BCM/TCM. The wires I labled in the crappy .Paint drawing are all stable voltages with the exception of the purple/white wire that I am getting these readings from. This is the one I believe I can tap into to mimic the switches located in the shifter assy. Make sense?

 

I'd try this myself. I didn't calculate the resistors yet... too lazy at the moment. Do you also get a voltage change when selecting auto / manual mode or overdrive disable (if it has that)?

If it's based on current like Strantor mentioned it's going to take a bit more than this and it's outside my range.

I say the 2.75 V for input for reasons I mentioned above.

 

I'd try this myself. I didn't calculate the resistors yet... too lazy at the moment. Do you also get a voltage change when selecting auto / manual mode or overdrive disable (if it has that)?

If it's based on current like Strantor mentioned it's going to take a bit more than this and it's outside my range.

I say the 2.75 V for input for reasons I mentioned above.
View attachment 142104

It has PRND then you slide it to the right while in drive and it lets you shift up or down. When its in the left position, the Pink/White wire is at 0V

 

You can get a voltage reference IC if you want a solid specific voltage to start with, that will eliminate the fluctuation issues you're worried about as the battery voltage goes up and down. I've used this one for 5v and it works really well:

https://www.digikey.com/products/en?keywords=LT1236BIS8-5#PBF-ND

I'm no automotive controls expert, but it seems odd to me that they would use analog voltage levels like that as control signals. We need someone from the automotive industry to chime in with some feedback.

 

Currently, I have a M/T mode on my automatic.

You said this in the first post. Why not take wires going to the manual part of the existing shifter and extend them to the paddle shifter?