Hello everyone, I am working on a F20B+T2T4 swap into a 1998 2.3CL with a manual trans. Since I have a full engine harness and PCB ECU for the F20B I will be simply re-routing the harness to the correct side and extending anything that is too short and running the JDM ECU.

My question is, what can I unplug from the CL ECU without throwing any codes? I want to keep everything OBD2 compliant and keep cruise control so I will be running both ECUs at the same time in parallel. Using the CL diagram, the only things I can see that I can unplug are the injectors, is there anything else that the ECU doesn't need to see to function? Basically I just want to use the JDM PCB ECU as a piggyback without the CL ECU interfering with fueling, spark, or vtec.

Thank you in advance

 

if the main goal is to keep it obd2 compliant, sorry, not gonna happen.
can you run them parallel? yes. but you'd need to remove every single output wire from the CL ecu. which essentially completely deactivates the whole ecu.

 

The main goal is to keep cruise control, since my assumption is that the CL ECU is outputting something on A5, but I haven't been able to find out what. if it's an input, and cruise will work without it connected, then I am not too worried about it.

What would be the reason that you couldn't connect all the sensor inputs to the CL ECU? Would splitting sensor inputs not work?

Correct me if I am wrong but in my head the ECU works like this: sensor input - decision for an action(open injector/close solenoid Etc..) - output signal(to injector/solenoid Etc...)

Does it receive feedback from any output devices? Looking at the pinout, I can't see how that's possible, since output devices are all single pin, and the engine electrical environment is to noisy for the ECU to be able to detect the signal being routed back to ground(which doesn't make sense anyway, as the engine is not isolated)
If you disconnect only the output devices, the ECU shouldn't be able to tell, and while sure, it won't be able to make changes to AFR or spark advance(does Honda even use the ECU for that? or is that all in the distributor?) and it might eventually freak out since it can't change anything, but, since it can't change anything, who cares?


Does this matter though? It wouldn't be controlling anything other than the secondary O2 sensor and possibly the cruise control. As long as it thinks its getting it's inputs it should output that everything is OK, right? The other thing with the AFR, as it stands right now, the commanded AFR by the ECU is not the same as the actual AFR anyway, and the ECU has no way to tell without a wideband. As long as it's close I don't think the ECU is going to care, but I could be wrong.

Possibly the reason I am confused is that I don't know how the ECU "sees" the sensors, and if the sensors go low or high to indicate the information the ECU needs.

Tthanks for your help,