Hi Ron,
Thanks for your help with this.

My tachometer is working normally, but I do want to check the voltage coming off of it so thanks for the info on the ICM.

The VTEC light is connected to the VTEC Solenoid lead (green/yellow B12 pin off the ECU) and grounded to the chassis. The B12 pin is also where I measured the voltage output from the ECU.

Unfortunately I don't have any Civic buddies in LA, but we do have a crap load of pick-n-pull yards. I hit them last week and didn't find any 96-00 Civic EXs. They rotate in freshly smashed vehicles about every month and I am planning to visit them again in April.

The last time I went the only thing I got was a huge bolt through my tire :\

 

So both the VTEC light or your multimeter were hooked into the Grn/Yel wire at the rear side of the ECU connector? If so, might the problem alternatively be a loose contact between ECU terminal B12 and the corresponding terminal in the ECU connector?

 

Hi Ron,
I don't think so. If it were shorted I think it would be dropping in and out of VTEC, I guess one way to check would be to wiggle the connection while the ECU is pumping 5.6v to the solenoid and see if it suddenly jumps to 13v. I'll give it a shot, thanks

 

I wasn't thinking of a short but rather intermittent poor contact between the connector terminals, thereby increasing resistance and reducing current flow.

Where exactly is the VTEC light wire spliced into and what did you touch with the multimeter probe to measure voltage. I am trying to identify other possible causes for the problem besides the ECU, even though in the end it may be responsible.

 

Hi Ron,
I plugged the multimeter probe into the connector for B12, so I was running the DMM off the pin B12. Of course if that connection is bad this test would suffer from it. The light is tapped into the wire coming off B12 a few inches behind where the B terminal connector plugs into the ECU. The problem existed before the light was installed. Let me get a picture for you, easier to show:

 

A picture shouldn't be necessary as I understand what you are saying. If the b12 terminal connection proves to be fine, then try an ECU swap, as you have already mentioned.

 

You wouldn't happen to have access to a circuit diagram of the ECM would you?

 

No, just the ECU pin out found in the 96-00 service manual, which you can download from the link in my signature.

 

Im having the same problem in my crx.. Only mine will cut in and out of vtec, it never works constant like it should.. I got the old obd0, got a obd1 ecm just waiting on a dizzy and wire conversion and hopefully it will all be good after I do the swap

 

I changed my ECU today and it fixed my problem. Took a while to find a replacement, finally found a person selling one on Craigslist. I picked it up for $40. Thanks for all your help in solving this Ron.

And Boost20 sounds like you have a loose connection or a short some where. Try bypassing the VTEC solenoid lead with a different wire. It could also be one of the inputs into the ECU with the short. You'll have to check each