tach learning on 4.7l 2001grand cherokee

I'm trying to install an Audiovox Prestige APS 601 remote car starter in my 2001 grand cherokee.  There are separate coils for each cylinder in the V8, so the instructions for the 4.7L V8 say to connect to any ingition coil wire that is not dark GREEN/ orange.  I've tried two different coils that fit this requirement and the system will not "learn" the tach.  I get the error or 7 flashes from the system which corresponds to "tach not learned."  Is there a better place in the vehicle to acquire the tach signal - perhaps somewhere in the cabin at a computer interface?  If connecting to a computer is not an option, is is possible that I need to connect to muliple coils??  Thanks

I have tested the wire at the ignition coil and it seems correct.  The remote starter instructions are below for the tach wire.  I'm worried that for this engine (which does have a single coil for each cylinder), that I'll have to hook up to multiple coils for proper tach reference.  The wiring for multiple coils is not clear in the unit's instrucions.  Therefore, I'm really looking for an alternate source (like the ECM) that I can hook up the unit to so it can monitor the tach properly.  Is there another location on a 2001 Grand Cherokee that I can monitor the tach besides the ignition coil?

"This wire will continually monitor the engine's tach rate while the unit is under power of the Remote Start module. This wire will be routed to the vehicle ECM tach input or through the firewall into the engine compartment and connect to the negative side of the ignition coil. This Remote Start unit learns the tach rate of the vehicle and in most cases will operate properly from one multi coil pack regardless of the number of cylinders. If the vehicle has a single coil unit for each cylinder, it may be necessary to connect this wire to more than one cylinder for proper tach reference."

Thanks.  That is exactly what I have tried so far.  I've tried two different coils using the uncommon wire on the coils (the non-dark GREEN/ orange wire).  I was not able to train the unit of the tach using either coil.  Do I need to have it hooked up to multiple coils at one time to learn the tach?  If so, how exactly do I do that? 

Is there not a location in the computer that I can hook up to on this type of car?