From the electronic manual:
27.2 External LED’s
The XFI ECU features LED’s built into the case. They are a valuable tool for confirming basic ECU functions. Because they are built into the ECU, they can be used without connecting a PC to the ECU.
27.2.1 Power
This LED lights up when the ECU is keyed on. If this LED is not lit, the ECU will not start the engine and will not communicate with a PC. If this LED is lit when the key is on but not when you crank the engine, you have not wired the +12V SWITCHED wire in the main harness to the right place in your vehicle.
27.2.2 Crank
This LED lights up when the ECU receives a crank input. It should flash whenever the engine is cranking or running. If it is not flashing, you will need to find out why before the engine will run. Check the source of the crank signal (crank pickup, distributor, stock ignition system, etc). Also check the wiring between the ECU and the crank signal. The flashing may be so rapid that the LED will appear to be continuously lit. This is normal.
If unexpected flashes occur (with engine running or stopped), it may indicate that the unused crank input has not been grounded.
The ECU will accept either discrete/Hall Effect or inductive type signals as its crank input. There is a separate ECU pin for each type. The inductive crank input is ECU pin A4. It can be found as pin A in the CRANK connector on the main harness. The discrete/Hall Effect crank input is ECU pin A8. It can be found as pin F in the CAM HALL EFFECT/HEI connector on the harness. Whichever input is not being used should be connected to ground. This will prevent the unused input from floating and falsely triggering the ECU.
27.2.3 Cam
This LED lights up when the ECU receives a cam input. In sequential mode with a cam input, this LED should flash whenever the engine is cranking or running. It will not flash as quickly as the crank LED does. It should flash once every two engine revolutions. Just like the crank, the flashing may be so rapid as to appear to be continuously lit. This is normal.
In Bank-to-Bank mode, a cam input is not required. So it is normal for the cam LED to remain off.
If unexpected flashes occur (with engine running or stopped), it may indicate that the unused cam input(s) have not been grounded.
The ECU will accept either discrete/Hall Effect or inductive type signals as its cam input. There is a separate ECU pin for each type. The inductive cam input is ECU pin A3 and can be found as pin A in the CAM/HALL EFFECT connector on the main harness. The discrete/Hall Effect cam input is ECU pin A7 and can be found as pin C in the CAM/HALL EFFECT connector on the main harness. Whichever input is not being used (or both inputs if no cam sensor is being used) should be connected to ground. This will prevent the unused inputs from floating and falsely triggering the ECU.
27.2.4 Points
This LED lights up whenever the ECU commands the ignition system to fire. Again, the flashing may be so rapid as to appear to be continuously lit. This is normal. If your engine will not start and this LED is not lit while cranking, first check to see if the Crank LED is lit up. More often than not if your ECU is not sending a points signal, it is not seeing a crank signal as the root cause.
27.2.5 INJ’s
There are 8 LED’s labeled INJ A through INJ H. These are wired directly to the outputs from the 8 injector drivers. Each LED should flash when the corresponding injector is fired – which should be whenever the engine is cranking or running. In Sequential mode, the LED’s will each flash one at a time. In Bank-to-Bank mode, INJ A, B, C and D will flash together and INJ E, F, G and H will flash together.
If you notice one of the injector LED’s is noticeably brighter or dimmer than the rest, it may indicate that one of the injectors is not securely connected to the wiring harness. Or it may indicate that the injectors are not all the same since the brightness of these LED’s will depend on the impedance of the injectors. Higher impedance will result in brighter LED’s.
These lights must be flashing... or appear on continuously for it to crank.