Just finished up my VQ35de swap in my 240sx, everything was working wonderful. I decided to play around with getting the tach to work, and hooked up the ground of the cyl.5 ignition coil for a signal. Well, obviously I am missing something because the ignitor starting smoking and when I replaced it, the same thing happened, ONLY to this cylinder, after the tach is disconnected.... So, I am assuming that I blew a transistor in the ECM... 500$+ mistake, lovely... The ECM is also spitting a P0300 code, not that there's really any significance to that. Anyways, I am getting ready to find a new ECM unless someone can tell me I have another option, IE fixing the ECM?

 

Be very careful next time -- use a resister in line with the tach so you don't cause another dead short on the ECM output. It's very likely you need another ECM now. 0300 is the result of running on 5 cylinders.

 

Yea, I figured, I just didn't know if there was anything on the ECM board that could possibly be replaced. Seems like the ECM is perfectly functional besides the Cyl. 5 Ign. Driver... The ECM cost isn't bad, found one for like 85$... the Osiris reflash is the ball crusher... Atleast 300$ just to get the NATS removed... I assume there is no way to transfer that license, eh?

And any idea about the tach, if that is going to be functional now? And any idea on where to start with the resister? I'm extremely good at basic automotive wiring, I did all the wiring for the swap myself. However, once electrical theory, etc. is involved, I ain't **** . I was hoping I could just hook up the neg side of the coil like I did to the tach and just have it reading 33% higher on the stock 240sx tach in hopes of avoiding the 80$ Dakota Digital converter. Would this converter also prevent my ECU from getting blown? I'm almost tempted to get an alternator based signal generator to avoid using the ECM circuit altogether in hopes of avoiding this type of thing again... costly mistake PLUS now I'm missing the SCCA event this Sunday that I was going to be my first. Really, the whole purpose of building this car... argh.

Anyways, I appreciate the input anymore offered

 

Good news, Osiris License can be transferred so since the ecm isn't a complete goner, I can send that in with a new ECM I buy and they can transfer the license. The dealer I talked to did say that they can't transfer the tune so they would charge me alittle to do that, can anyone verify that?

Also, I'm still confused why it blew. I talked to a Dakota tech to see if their converter was all I needed or if I was missing something. He said he had no idea why it would have blown. I would like to figure it out before I try and hook the tach up again so I don't have to shell out for another ECM...

 

It's not the ECM.... paid 100$ to get someone to tell me it wasn't the ECM ><...

So now I need to look for shorts on the harness I guess? Like I said, I pulled off of the negative side of the coil, so wouldn't the problem have to like within that wire? The wiring diagram shows it running directly back to the ECM? I can get my multimeter out but not sure really where to start...

O, and I bought another ECM so if someone needs one, 100$ + shipping and its yours !!

 

Ok, so I thought that I intially had only fried the coil that I had spliced off of, but actually I fried several. So, when I switched out that one single coil, there was still a short in the ignition circuit so that coil fried again. I ordered some new coils, but now what do I need to do to get the tach working and why did the coils fry in the first place?