AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 145)

Page 145 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
The A Tooth channel counts from 0 to 57 then resets. The Fuel Tooth channel counts from 0 -
11 then resets (one loop through the tooth control table or 12 edges). A simple PC log like this
recorded during cranking can be very helpful in troubleshooting timing pattern problems.
Noise
Electrical noise can cause the EMS to see more tooth edges than there are in reality. This will
result in excessive “Timing Errors” during cranking or constant errors during normal running.
Misfire caused by “noise,” (commonly referred to as radio frequency interference {RFI}, or
electro magnetic interference {EMI}), is usually due to routing the input signal leads in close
proximity of the HT leads. Typically, spark plug wires cause RFI or primary ignition wires arcing
to an engine component, which causes a frequency that interferes with the ECU. Routing two
wires that carry high current parallel to each other cause EMI. The strength of current necessary
to incur “noise” is dependent on the sensitivity of the device the wires are connected to. A
Crank Tooth
Period Missing
Tooth Section
Cam Tooth
Edge
Detected
Crank Count