Hondata

I am trying to understand why my EFI main relay won't turn off. This is a KSwap into a MR2 spyder with a KPro4, and I have the ECU and relay wired up properly to the KPro E7 pin, so memory power is supplied through the relay coil. I believe the ECU is supposed to internally switch to grounding the relay coil circuit to energize the EFI relay, but how does the ECU get the signal to turn off? I assume the Honda ECU has an internal relay to switch the E7 pin.

I figure it could be through E pin 9, IG1 ignition signal, but my testing shows this does shut turn to 0 volts with the key-off. Does anyone know how the ECU gets the key off signal to turn off the EFI relay?

Dave

From E9. Once the ignition voltage to E9 is switched off, the ECU will switch off the main relay via E7. If it is not then either the ECU output transistor is damaged on permanently on, or the main relay output is latching back into E9. I've seen that if the o2 sensor relay power is not switched.

Thanks; I retested and see that E9 only goes down to 3 volts at key-off and if I disconnect the the O2 sensor connector, it goes to zero and the relay shuts off.

Dave

Make sure that the o2 sensor relay power source is switched ignition, not the main relay output.