Here some more info for the control of the module:
IGN REF HI– (typically 3X on an L4 or V6, 4X on V-8) This is a digital input from the ignition control module to the PCM and based on the VR sensor (DIS) or Hall effect (C3I) sensor inputs to the ignition module. The PCM uses this signal to calculate engine RPM and crankshaft position. The PCM compares pulses on this circuit to any that are on the Reference Low circuit, ignoring any pulses that appear on both (passive filtering).
The PCM also uses the IGN REF pulses initiate injector triggering. In MPFI startup there will be 1 batch fire of all injectors every trailing edge of reference (ie HI to LO transition) but once running (400+ rpm) the injectors will only be triggered once every engine revolution (2 per 4 stroke cycle). If the V6 engine is equipped with SFI, once above 400 rpm, a single injector will be triggered every 120 degrees of crankshaft, in firing order.
BYPASS- This is a PCM output to the IGN Module. During cranking the PCM allows the ignition control module to keep the spark advance at a default/base (typically 5-10° BTDC) this is called BYPASS MODE. During BYPASS MODE the PCM applies 0Volts on the bypass circuit. Once above 400 rpm, the PCM commands the ignition module to allow the PCM to control the spark advance (aka EST or IC Mode).To accomplish this the PCM applies a 5V signal on the bypass circuit to trigger a transistorized switching circuit within the IGN module, connecting the EST circuit to the coil primary control FETs. If the PCM does not apply 5 volts to the bypass circuit, or if the ignition control module does not sense the 5 volts, the ignition control module will continue control spark timing (Bypass Mode) at or near 5-10° BTDC.
EST or IC- This is a digital output from the PCM to the Ign Module. In BYPASS mode this circuit is typically grounded through a fixed resistance within the IGN module. Once 5V has been correctly observed by the IGN control module it will “switch” to EST or IC mode and connect this signal to the primary FET circuits controlling each waste-spark coil pack. This signal is essentially identical on the IGN REF but is “delayed” in order to provide an appropriate amount of advance based on numerous inputs such as RPM and manifold pressure (MAP). ZERO delay will result in “base” timing (ie 5-10° BTDC) but by delaying the EST/IC signal the PCM can create the appropriate amount of ignition advance for the “next cylinder” coming up on it’s compression stroke.
IGN REF LO- This is a PCM input or more correctly a ground “offset” circuit connected between the PCM and IGN module. This is a low reference circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only through the ignition control module. Although this circuit is electrically connected to the PCM, it is not connected to ground at the PCM. The PCM compares voltage pulses appearing on the IGN REF input to those on this REF LO circuit, ignoring pulses that appear on both, which is likely due to Electro Magnetic Interference (aka “noise”) thus allowing this interference to be filtered out and ignored.
TACH – This is a periodic voltage signal suitable for driving the oem tachometer (if equipped) The frequency applied will vary with the number of cylinders and/or gage requirements. The circuit usually includes various filtering devices (low/high band pass) in order to improve tachometer performance.
GND – This is the primary ground connection for various electronic circuits within the IGN module itself.. The IGN REF LO circuit of the PCM will also find it ground here. NOTE: Some C3I and DIS IGN module circuits may also require correct grounding through the module mounting.
Now I'm looking at the software for the 1280, I see that the Northstar firing order isn't in the pulldown (1-2-7-3-4-5-6-8) is there a way to modify that? I understand that it actually doesn't matter for waste spark since the pairing is the same, but maybe later after I figure out a way to use the stock sensors with coil-on-plugs.