# rpm signal Cable



## thygreyt (Jun 7, 2009)

Guys, i'm in the middle of doing some stuff to the car and i need to find out which cable do i have to tap to get the RPM signal.

i was thinking on tapping something near the sparkplugs, but i just dont know which cable is for what.

does anyone of you knows? or does anyone knows where can i get the rpm signal?

people are saying that there should be a wire in the 90* bend after the coilpacks... well, here










but which cable in there? no clues.



















i know this is s pic of the 2.0t, but who knows where to get the rpm from in the 2.5?

the bentley manual shows where is the sensor located, but it doesnt tell me which wire to tap


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## johnathon ross (May 12, 2009)

thygreyt said:


> Guys, i'm in the middle of doing some stuff to the car and i need to find out which cable do i have to tap to get the RPM signal.
> 
> i was thinking on tapping something near the sparkplugs, but i just dont know which cable is for what.
> 
> ...


If you look at the plugs on the coils i'm pretty sure that pin 3 is the firing pin for coils you will be able to sample 1 cylinder if you connect it up however you will only get 20% of actual rpm.


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## thygreyt (Jun 7, 2009)

then where can i get full rpm?? i'm installing some fun things, and i need full clear RPM signal. where can i get it?
which cable do i have to tap?


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## thygreyt (Jun 7, 2009)

??


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## TeamZleep (Aug 28, 2007)

I'll go ahead and be nosy. What fun things?


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## thygreyt (Jun 7, 2009)

Hoepfully I'll have it done by sowo, and you'll be able to see.
Right now I need to know where to get rpm from.

But all I can say is that I have been talking to some companies about some good na dev.


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## johnathon ross (May 12, 2009)

rev counter signal will be sent via can bus to instrument cluster - so it maybe tricky


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## thygreyt (Jun 7, 2009)

can bus? that would suck.

i know where the rpm sensor is located. but i dont know where to tap a wire that would give me the RPM voltage.


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## thygreyt (Jun 7, 2009)

i have a 2.5 2009 engine CBTA.

the exact thing i need is one of the following wires:

-low voltage side (-) of primary ignition coil
-digital engine tachometer


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## thygreyt (Jun 7, 2009)

engine: 2.5L I5 CBTA

















































CorradoG602 said:


> This is for a CBTA from June 2009 there is a vin split in 2009 for the CBTA
> 
> The large 2.5mm red/green tracer is the power which is has a common crimp and branches off to 5 1.5mm same color wire to each coil cavity 1 on each coil connector. Same thing with the brown which is ground cavity 2 on each coil connector. The 2.5mm brown/green wire is a ground possibly bolted to the engine somewhere, same thing common crimped and is cavity 4 in each connector. Coil 1, cavity 3 lilac/brown tracer goes right to the ECM. Coil 2 cavity 3 lilac/blue tracer goes directly to the ECM. Coil 3 cavity 3 blue/yellow tracer directly to the ECM. Coil 4 cavity 3 lilac/green tracer goes right to the ECM. Coil 5 cavity 3 lilac/black tracer same thing......right to the ECM
> 
> ...





CorradoG602 said:


> From elsa web the VW online repair manual. I'm gonna have to say the wires in cavity 3. The ones that go directly to the ECM. So there are 5 components to this 1 is the constant power which is the red/green tracer, goes to the SB fuse box and is powered by the ECM power relay (power) Next is the solid brown wire.....Ground which goes to the electronic fan control (shares same ground) Next is the brown/green tracer.....another ground for the harness. Its common crimped and is grounded/terminated to somewhere in the engine bay (I'm thinking to the cylinder head or something like that) The diagrams never tell you. Lastly are the wires in cavities 3 that go to the ECM. I'm gonna use the color codes on the diagram now for this. So we have power (ro/gn) We have ground to the body (br/gn) We have another ground (br) to the cooling fans.....why I don't know and am not german. Lastly We need a signal where is this signal coming from?????? Ah ha the ECM which is the wires for cavity 3 on the coil harness. The ECM sends a pulse travels through that wire and tells the coil to fire the plug since we already have power and ground. So you are wondering why I said we have 5 components to this? Its the spark plug which is the 2 triangles with the box around it and I know that grounds out to the cylinder head. So long story short I wanna say you are looking for the wires in in cavity 3. I don't know what you are doing with this but I would say back probe that wire first to make sure whatever you are doing works. And if it does then do a final connection. Unless I think you wanna tap off the RPM sensor G28 that reads the reluctor wheel off the fly





thygreyt said:


> so, cavity 3 goes independently or crimped to the ecm?





CorradoG602 said:


> Yep.
> 
> And cavity 3 goes independently directly to the ECM. No crimps no nothing, straight wire. Each one from what ever cylinder has its own position on the ECM
> 
> cylinder 1 is terminal 50 on the 60 pin connector at the ECM cylinder 2 is terminal 35 cylinder 3 is terminal 33 cylinder 4 is terminal 49 cylinder 5 is terminal 34. BTW when you put the engine to top dead center cylinder 1 is NOT top dead center CYLINDER 5 is TDC. Thats how the 2.5 works


pretty much wanted to put it all here on the 2.5 tech if anyone in the future needs it.


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## Audi4u (Jun 29, 2002)

I apologize I wanst able to post a response earlier. There is no real rpm wire on cars after ~ 2004.

Depending on which type of signal you need you could use the main ground wire to all coils or the trigger wire from the ecm to any coil.(doesn't have to be cyl5). 

While the trigger from the ecm works please use extreme caution with working with any input\output directly from the ecm. Any improper connection could render the ecm usless or damage the input\output.

If you ever had to change the ecu on a immobilizer car you will know that it is a very involved process only avilable via the dealer, and of course if you have a chip\flash is gone with the old ecu. 

Andre


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## thygreyt (Jun 7, 2009)

Audi4u said:


> I apologize I wanst able to post a response earlier. There is no real rpm wire on cars after ~ 2004.
> 
> Depending on which type of signal you need you could use the main ground wire to all coils or the trigger wire from the ecm to any coil.(doesn't have to be cyl5).
> 
> ...


 i was told to use signal from the injectors. lol. to leave ignition alone


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## kevin splits (Aug 23, 2010)

Audi4u said:


> I apologize I wanst able to post a response earlier. There is no real rpm wire on cars after ~ 2004.
> 
> Depending on which type of signal you need you could use the main ground wire to all coils or the trigger wire from the ecm to any coil.(doesn't have to be cyl5).
> 
> ...


he has it right, ground with the main ground wire, *or trigger wire from ecm BUT i would maybe drop some money on a used ecm from ebay to do the little trial and error, cuz frankly losing your tune is no fun.

it would be easier to help if i knew what ur doing. are u looking to retro in a harness to some electronic, or two wires for a gauge?


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## thygreyt (Jun 7, 2009)

so, main ground would work for tach?


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## kevin splits (Aug 23, 2010)

i think to do it from the trigger wire, u would tap into the red/green power wire before it branches off to the five coils, and then ground with the brown/green. again not 100% sure just a logical guess looking at the jetta wiring diagram.... but that is for a 2.0t 

it does say u can tap that product into the tach.. tht may be an easier option, and locate the product inside the cabin :thumbup:


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## thygreyt (Jun 7, 2009)

kevin FaKiN spLits said:


> i think to do it from the trigger wire, u would tap into the red/green power wire before it branches off to the five coils, and then ground with the brown/green. again not 100% sure just a logical guess looking at the jetta wiring diagram.... but that is for a 2.0t
> 
> it does say u can tap that product into the tach.. tht may be an easier option, and locate the product inside the cabin :thumbup:


thats a diagram for the 2.5, but the 5th cyl is on page 2
i saw no point on posting page 2 where it only has 1 cyl/plug


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## johnathon ross (May 12, 2009)

there maybe a cruise control pin you can tap into and get a pulsed output i think it might be pin38


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## kevin splits (Aug 23, 2010)

ah ok. the diagram 131/9 looked like a closed wiring circuit, looking like a 4 cyl.


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## thygreyt (Jun 7, 2009)

kevin FaKiN spLits said:


> ah ok. the diagram 131/9 looked like a closed wiring circuit, looking like a 4 cyl.


131-10 is the fif cy, and 131-13 is for the injectors


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## thygreyt (Jun 7, 2009)




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## Audi4u (Jun 29, 2002)

thygreyt said:


> so, main ground would work for tach?


Some older vw tachs and some msd products read the high voltage surge\current surge that travels over the main COIL ground. This groud is wat closes the circuit of the primary side of the coil.

Not trying to confuse anyone. 

I guess the quesion is what are you trying to do?


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## thygreyt (Jun 7, 2009)

Audi4u said:


> Some older vw tachs and some msd products read the high voltage surge\current surge that travels over the main COIL ground. This groud is wat closes the circuit of the primary side of the coil.
> 
> Not trying to confuse anyone.
> 
> I guess the quesion is what are you trying to do?


pmed.


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## darkk (Jun 22, 2006)

All VW's come with a factory Tachometer. Just look up the wiring diagram for it......:screwy:


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