Serial Data Link (Pin 7 on the OBD2 port). Used for diagnostics.

The EDU processes these signals, steps up the voltage, and fires the injectors.

| Component | Test Condition | Normal Reading | Abnormal Reading (Indication) | |:---|:---|:---|:---| | | Engine off, key on engine off (KOEO) | 0.3-0.7 ohms (resistance across its two pins) | Open circuit (∞) : Broken SCV coil or wiring Short circuit (0) : Internal short | | Fuel Injector (#1) | Engine at 20°C (68°F) | 0.85-1.05 ohms (resistance across injector terminals) | Low or high resistance : Injector is faulty and may need replacement | | MAF/MAP Sensor Signal | Ignition ON (engine OFF) | Approximately 0.5-1.5 volts (reference voltage) | No voltage : Blown fuse, no ECU power, or broken wire | | MAF/MAP Sensor Output | Engine at idle (warm) | Specific voltage depending on load, typically 1.0-2.5 volts | Voltage too high/low : Clogged/dirty sensor, vacuum leak, or wiring issue | | ECT (Engine Coolant Temp) | Engine at 20°C (68°F) | Approximately 2.0-3.0 kilohms (resistance across ECT sensor pins) | Incorrect value : Faulty sensor, wrong sensor type, or wiring issue | | Engine Ground (E1, E01, E02) | Engine off, key off | Less than 1 ohm resistance from ECU ground pin to battery negative terminal | High resistance : Dirty/corroded ground connection or broken ground wire | | CAN Bus (CAN-H to CAN-L) | Engine off, key off | 60 ohms (with all modules connected on the bus) or 120 ohms (if terminating resistors are missing) | Open circuit (∞) : Broken CAN wire 0 ohms : Short between CAN-H and CAN-L |

These pins receive varying voltage signals from the engine block to calculate fuel mass and timing:

Wire the M-REL output pin from the ECU to trigger the coil of your custom EFI relay. This relay should then feed clean 12V power back into the +B and +B1 pins.

OBD2 (K-Line or CAN) and the EDU trigger signals. Primary Pinout Functions (Common Denso 104-Pin/134-Pin)

Understanding what each wire does is essential for troubleshooting. Here are the most critical pins: