AEM 30-6030 Series 2 Plug & Play EMS - Manual (Page 9)

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6) Troubleshooting an engine that will not start
a) Double-check all the basics first. Engines need air, fuel, compression, and a
correctly-timed spark event. If any of these are lacking, we suggest checking simple
things first. Depending on the symptoms, it may be best to inspect fuses, sufficient
battery voltage, properly mated wiring connectors, spark using a timing light or by
removing the spark plug, wiring continuity tests, measure ECU pinout voltages,
replace recently-added or untested components with known-good spares. Check that
all EMS sensor inputs measure realistic temperature and/or pressure values.
b) If the EMS is not firing the coils or injectors at all, open the Start tab and look for the
‘Stat Sync’d’ channel to turn ON when cranking. This indicates that the EMS has
detected the expected cam and crank signals; if Stat Sync’d does not turn on,
monitor the Crank Tooth Period and T2PER channels which indicate the time
between pulses on the Crank and T2 (Cam) signals. Both of these channels should
respond when the engine is cranking, if either signal is not being detected or
measuring an incorrect number of pulses per engine cycle the EMS will not fire the
coils or injectors.
c) If the Engine Load changes when the throttle is pressed this usually indicates that
there is a problem with the MAP sensor wiring or software calibration (when the EMS
detects that the MAP Volts are above or below the min/max limits it will run in a
failsafe mode using the TPS-to-Load table to generate an artificial Engine Load signal
using the Throttle input). This may allow the engine to sputter or start but not continue
running properly.
Sufficient battery voltage during cranking (starting)
Having enough battery voltage when you crank over your vehicle is critical to the
operation of your vehicle and your AEM EMS. For the EMS to function properly, the
battery voltage must remain at or above 8 Volts when the vehicle is first starting. This
is the time when your electrical system will be worked its hardest and be at its lowest
voltage. If you are connected to your Series 2 EMS with a USB communications
cable, and you experience disconnecting while the vehicle is cranking, the reason
may be a battery voltage of less than 8 volts. If this is the case, you can confirm this
by connecting with a serial cable (a serial adapter may be required if your computer is
not equipped with a serial port) and check in the AEMTuner software for a Channel
called “Run Time”. “Run Time” is the amount of time, in seconds, that the EMS has
been turned on for. If you notice that this Channel goes to zero while the EMS is
communicating with the computer and the vehicle is being cranked, that means the
EMS has had lower than 8 Volts at some point and has reset the system. A thorough
wiring check may reveal a large voltage drop causing this problem, or it may simply
be the need for a new or a larger battery.