1G 1g ECU and MPI relay

[lotta hp]

What ic or diode would cause the ecu to not turn the mpi relay off?

 

[Colt4G63 also]

Don't rule out an improperly wired fan.

 

[lotta hp]

How can a improperly wired fan case the ecu to not switch the mpi relay?

It's the ecu 100%. I have a good working ecu in the car but this ecu does not shut the relay off after 10 seconds.

 

[Colt4G63 also]

A spinning fan generates voltage. If it's wired improperly, the fan can actually generate voltage to keep the relay on, and therefore everything keeps running.

 

[steve]

There isn't a diode in the circuit for the MPI relay coil except for the flyback inside.

The normal function is that ECU pulls the ground side of the coil low to turn the relay on. So anything that grounds that pin will keep the relay on. Even though the ECU might work otherwise this is a common failure.

What happens when you unplug the center connector on the ECU? If the relay turns off you have a damaged ECU.