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Unread 12-31-2013, 02:26 PM   #1
Project1
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1998 XJ Cherokee 
 
Join Date: Feb 2010
Location: Florida
Posts: 2,716
Tach wire

Does anyone know where the tac wire is. I think it comes off the distributor but I'm not sure what wire it is. Any help would be awesome

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Unread 12-31-2013, 03:59 PM   #2
green97xjsport
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1997 XJ Cherokee 
 
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Not sure on the 98, I know for older ones, you can pick up the signal from the black wire I think from the coil if you're talking about an aftermarket coil, I know the factory tach coverts it signal from the power control module. Not familiar with the 98, does it have a single coil, or multiple coil packs?
I'm sure a 98 owner will chime in.
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Unread 01-02-2014, 11:35 AM   #3
madmax85
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1989 MJ Comanche 
 
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I believe the tach wire for the gauge actually comes from pcm/ecu. If you are running an aftermarket tach you could splice into the negative on the coil
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Unread 01-02-2014, 02:05 PM   #4
holysirsalad
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Quote:
Originally Posted by madmax85
I believe the tach wire for the gauge actually comes from pcm/ecu. If you are running an aftermarket tach you could splice into the negative on the coil
+1 at least on OBD-II, the dash uses the signal from the CPS.
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Unread 01-02-2014, 09:49 PM   #5
sAe23
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1995 XJ Cherokee 
 
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I was wondering about this for my 95 (ODB1)... Where does the ECU get its signal? I glanced through the FSM but didn't find anything (not sayin it wasn't there, just...)
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Unread 01-02-2014, 10:11 PM   #6
holysirsalad
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From the CPS
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Unread 01-03-2014, 08:01 PM   #7
madmax85
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1989 MJ Comanche 
 
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what are you needing to know for? i put megasquirt on my comanche and when i hooked the factory tach up to the coil negative it reads 1.5 times the actual rpm. so in a basic sense the computer sends a 4 cylinder signal to the gauge cluster for the tach. its really weird.
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Unread 01-04-2014, 02:52 AM   #8
sAe23
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If you are asking ME, I was just curious. I had two isolated instances of a momentarily dead tach and started to wonder about how it all worked...
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Unread 01-04-2014, 12:01 PM   #9
madmax85
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1989 MJ Comanche 
 
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i gotya, glad to help, and just some fyi info for ya
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