Hi folks, I have a 2000 SI that has been swapped to a B18C5 from a 98 JDM Type R; however, I'm pretty sure the engine harness is still the EM1 harness. The ECU in the car is a P73, which is also from a 98 JDM Type R, and has a jumper harness connecting it to the engine harness. That being said, it is an OBD2A engine/ECU in a OBD2B chassis. All of this work was completed when the previous owner owned the car. The issues I am currently facing are the tach not functioning, though it will very occasionally jump around, and VTEC not activating, or so it seems.

One thing I noticed about the engine harness vs. the engine, is the distributor plugs are not matching up. Both are the 9-pin plug design; however, the engine harness side of the plug does not have a pin for the RPM signal wire. So the distributor has 9 wires coming from it, but the engine harness only has 8. I read several threads where individuals were able to jump the RPM signal wire to the RPM test connector and get the tach working. I tried this, and had no luck. I am assuming this wiring issue is causing both my problems. Has anyone encountered this issue and what was the solution.

Also, in the swap FAQ the author states not to mix and match 2A and 2B OBD systems as the ECU will not match the harness. I assume this is negligible though due to the jumper harness in the car?

Outside of the issues listed above, the car has not problems. Seems to run very well.

 

Alright, continuing down this path, I also do not have connectivity at the OBD2 port. After researching, the issue is the JDM ECU can not be scanned from the OBD2 port with a reader, and I will have to find a USDM P72 ECU. Along with this, should I be swapping to a distributor that is original to the car to solve the 9 wire issues?

The ECU in question is the 96-99 Integra P72 ECU.....

 

you can re pin the dizzy plugs as needed or get an adapter

if you are getting a check engine light (CEL), jump the service connect and pull the codes

the distributors are the same internally

 

So which wire on the dizzy is left unused? Like I said, the dizzy has 9 wires, the harness engine harness itself only has 8.

I have no CEL on.

 

I believe its the blue signal wire, I could be wrong I have no first hand experience

here this might be helpful

https://honda-tech.com/forums/honda-...2A%2A-2868178/

 

 

Yes, it is a car someone else swapped and the distributor has the blue tach wire, the engine harness does not though.

I have a P72-A04 OBD2A ECU as well, the car runs fine on that ECU and the OBD2 port now works. Still no RPM signal and no VTEC activation.

 

99-00 gets its rpm signal from the ecu.

em1 engine harness uses the 10 pin harness

 

So the ECU has engine speed signal, just confirmed that with the OBD2 reader. So the gauge and VTEC issue are likely unrelated and will need sorting independent each other. And right on with the tach getting it's signal from the ecu, found this out after a bit of research and also after testing the engine speed test wire. So I probably have an issue with the tach itself or the lead to the tach.

And right, the EM1 harness has a plug capable of carrying 10 pins, but does not actually have 10 pins. It only has 8.

 

no, the em1 harness HAS the 10 pin distributor plug. you have the wrong harness if you havent figured it out by now

 

Trying to upload an image that explains this. The plug is 10 pin or capable of 10 pins. But the distributor only has 9 wires and the harness only has 8 wires.

 

 

The em1 harness has the square plug already needed to use ANY b-series that came out of an integra. If you have a rectangle plug thats not the em1. you'll have to buy an adapter if you're not comfortable at repinning to the correct square plug. That simple.

 

Two things to check before you try another instrument cluster:

First, you need to verify that the jumper harness you are using has one wire piggy-backed from the ignitor and split off to the tachometer drive wire pin. This means that since an OBD-2A or OBD-1 ECU doesn't provide the tach signal like the OBD-2B ECU does internally, the tachometer on the instrument cluster must derive it's operational signal from another source. The ICM output wire (yellow/green) from the ECU provides the same pulse as the tach output wire from the ICM (blue wire from the bottom of the plug next to the black/yellow main power wire) from an earlier distributor. If this wire is missing in your jumper harness... you get no tach signal to the instrument cluster. Quality adapter harnesses like a Boomslang Fabrication harness have it... cheap Ebay ones may not.

Second, typical aftermarket distributors have low quality ICM's that cause interference in the wire pathway, and this can cause enough signal degradation to cause the tach in the instrument cluster to malfunction or not work at all.

 

I've already jumped from the tach signal wire to the test connection in the engine bay, that should have resulted in the tach operating normal, but it behaved the same as it has before.

On another note, I do not think the engine is a JDM Type-R engine, rather a US Type R engine.

 

If you plug in the ORIGINAL B16A2 ECU, how does the tach function ??? Your tach test port in the engine bay should function properly with the stock ECU as well. When you swap the ECU to an earlier platform type (OBD-2A or OBD-1) and use an adapter harness, where do you think the tach test port gets it's signal from ??? It makes no difference whether your engine is a JDM or USDM engine... so if your tach works properly with the stock ECU, your problem is likely electrical.