Hondata

I have a Honda em1 with a p28 and s300. I'm having a very strange problem I can't figure out. The car will start and run but very badly with cel light on. The smanager says ecm online but will not show codes or datalog. If I turn the key off and back on the car will run perfectly, cel goes off and smanager works as it should. It does this almost every time i start the car, as long and I start it and turn it back off the second or third time it starts and runs perfect. When the cel is on I can't read it with a scanner either. Does this seem like a ecm issue? The car ran fine last summer this just started after the winter. thanks for any help, I'm lost....

What is the serial number that is on the s300 board inside the ECU?

I'm not sure where the s/n is or is it the 23386?

From Help, About, what is the version of software you are using?

2.5.3.0

It sounds like it might be the capacitors going bad on the ECU. I would recommend replacing them.

https://www.hondata.com/products/access ... acitor-kit

none are leaking if that matters but ill give it a try. I'm getting frustrated to the point I want to just go back to stock.

Hope i'm not 'hijacking', this is the first time i've used a forum before so please excuse my lack of etiquette....i have followed the troubleshooting points and am thinking it's the ecu thus far- any\all help or comments are very appreciated.

motor- JDM B18C (94 or 95) OBD1, stealth 11542 fuel pump, rdx 410 injectors, aem fpr, pretty much stock from there aside from currently running a chipped P08 Mugen tune.

Bought a working P28 (i was 'told' it was working), installed the s300v3 (updated f.w.), i can upload the stock b18c basemap, i changed the injectors to the rsx 440s' as they were the closest match (and the rdxs' 410 are dynamic up to 550 from what i've read), i start the car- limp mode- poor running- solid c.e.l.- and no readings in smanager display. sometimes the ect and iat max out at 302 deg.f.

The ecu caps aren't blistered, my soldering is solid as i have past pcb experience. v3 #36466

Thanks in advance.

You really should start your own thread for this.

Is J12 cut inside the ECU?

J12 Has been cut, all installation instructions have been followed to a 'T'....

also- where do I start a new thread regarding this issue as per your suggestion? (told ya I was new to forum stuff!) ;o)

Ok, to bring an end to kicking this dead horse, the ECU was the problem. Just re & re'd with a new P06 and turned it into a P28, installed the S300, all is 100%.

Thank You for the support, and I'll do the new thread next time for sure. HONDATA FRIGGIN' ROCKS!!!!!!

Well I'm still having the same issue. I ended up using a new ecu and nothing changed. I have checked everything i can think of. Is is possible that the s300 itself is having some sort of issue? I have found no broken wires anywhere. I thought maybe there was and issue with jumper harness but I don't see any problems with it.

Have you tried your ECU in a friend's vehicle?

Sadly no one in my area has these cars anymore. I did notice with the car off if I turn the key to the on position the cel light off the green light on the s300 is on. If I turn the key back and on again cel comes on and the green light is gone. Repeat and cel is off and green light back on. Does this give any indication what's going on? I'm losing power somewhere. Could it be my key switch?

It sounds like you probably need to replace the capacitors inside the ECU.