Dekorum

Does anybody know why you have to run a separate wire to make the tachometer work on certain swaps? I am sure it has to do with the combination of body harness + engine harness, but I want to know for sure. I would like to know why I had to run a wire to my distributor plug from one of the connectors on the driverside shock tower for my tach to work after my swap

EJeff8

Well, you need a wire for the needle to sweep, a wire for the information, and a ground of course.

Dekorum

Yeah, its just one extra wire you have to run on certain swaps. I am just wondering why ..

EJeff8

Could be a pin change.

B18C5-EH2

Perhaps the lead on the ignitor inside the distributor that's off to the side (this is the tach signal) is loose or off?

CivicSpoon

'99-'00 Civics (excluding the Si and HX) have Engine Speed Output (signal for the tach) run off of the ECU, rather than the distributor. Where they have the 8-wire plug rather than a 9-wire plug. Does any of that pertain to the swap you're doing?

Maybe you should be a little more specific about what car you have, what harnesses & ECU you're using, and what engine you're putting in.

B18C5-EH2

He has a 1992 Civic Si HB with JDM B18C (Type R) and what is supposed to be a 1997 USDM Integra GS-R engine harness. Currently he's running a jumper harness and a JDM P73 ECU.

Dekorum

^^ Correct.
Except the engine harness I am using is supposed to be a USDM Type R harness. Not sure of the year though!

Dekorum

Any one else have any ideas?

Gunmetal_B20_Hatch

iTrader: (9)

light blue wire between DS shock tower and firewall?

Dekorum

Right, I believe that is supposed to be it. I am wondering WHY it did not control my tach once I dropped in the OBD2 Type R USDM harness like plug and play. I had to run an extra wire directly from the DS shock tower connector to the distributor connector. My tach works perfectly now. I am just wondering WHY I had to do it, when I have heard of others just using an OBD2a harness in an EG swap and it works the tach plug and play.

Gunmetal_B20_Hatch

iTrader: (9)

I would go with the above post by B18C5-EH2 about the difference in 8 and 9-pin plugs.

Dekorum

Well CivicSpoon said that about 99-00 Civics. I don't have anything from a 99-00 Civic in my setup..

CivicSpoon

Maybe something in this thread has something to do with it?

https://honda-tech.com/forums/acura-integra-type-r-8/jdm-itr-ecu-tach-signal-different-than-usdm-2118063/

The only other thing I can find from a search is a LOT of people having the same issue. But I haven't seen a single answer as to why. I wish I had a copy of the '98-'01 Integra ETM to check it out myself.

Dekorum

Hmm.. well I was running a P28 at first, and my tach still didn't work. So this may mean that the USDM Type R engine harness I bought from a friend is a 2000-2001 one? I know the engine is a 96 JDM ITR.

Dekorum

Wait, wouldn't there be a noticeable difference in the 97-98 and the 00-01 Type R engine harness? If I knew what they were, I would go out and check if I see any of them on my harness.

CivicSpoon

We didn't get OBD2A ITRs over here in N. America; the Type R's were only sold here in '00-'01 (OBD2B). There would be differences between the models, which could narrow it down. The GS-R would have wiring for the IAB and the LS wouldn't have wiring for VTEC. But as for OBD2A vs OBD2B harness differences, I don't know. Seems this may be one of those "little" things that the Honda community may not have a definite answer for.

Dekorum

Haha, maybe I can't get a definite answer. But I thought I would try.

Also, there definitely WAS an OBD2A ITR in North America. 1997-1998 did exist in America. Japan got the 1996 which we didn't. And the 1999 did not exist anywhere.

CivicSpoon

OMG, how did I not know that... I would have put $ on the fact that the Type R came here in '00. I don't know why I thought that.

Dekorum

Haha, you mean 99. Cause they did come here in '00!