Hello everyone, I know this topic has been covered probably a lot but I’ve read through most of the forums and havnt been able to figure out the problem. So I have a b18a1 in my 98 civic, running a p75 ecu. So my old harness for one reason or another was missing some plugs on the dizzy, also few other problems, so I picked up a newer uncut ODB2 harness and swapped it in this last weekend. Before I swapped harness in the car would start, fuel pump would prime all that good stuff. But now I am getting no power to ECU plugs, main relay isn’t clicking on or off, fan isn’t turning on even though thermostat plug is jumped, and fuel pump is not priming obviously because the ECU isn’t getting power. I have checked all my grounds, they are good, I have checked all my fuses, they are good, Have tried another main relay, nothing, I have tried another KNOWN working ECU from my friend and still nothing. Any help is much appreciated, this forum has pretty much helped me solve every swap problem I’ve had so far so thanks in advance.

 

Check hood fuse 44 and dash fuse 13.

 

Sadly they were both good.

 

Use a multimeter to measure voltage to body ground at both test tabs of the two installed fuses. Do both fuse tabs read battery voltage with key in ON(II)?

What fan are you referring to here^?

 

What year/model/trim chassis do you have and what is the year/model/trim of the replacement engine harness that you have now installed ?

 

my shell is a 99 ek coupe, harness came out of manual, 96-98 Civic dx, according to the seller.

 

the Radiator fan, I don’t run a thermostat, Atleast not in this build there is no need, so with my old harness I just jumped the black and green wire that usually is for the thermostat housing plug and the fan stays on as soon as key is on but I am getting nothing from the fan right now, all the cluster lights work also not sure if that helps any.

 

All the power to the items you are not getting power to comes through the engine harness via C101 on the drivers side shock tower. Check for voltage to ground on the yellow/black and black/yellow wires there.

there are pin differences between 96-98 (obd2a) and 99-00 (obd2b) harnesses that I cant remember without a diagram in front of me. I’ll look in the morning. The ecu pinouts and the c131 (green connector at ecu) are also pinned differently between the two. In fact, power/ground on the 2a ecu comes in to ECUA and 2b comes into ECUB, so you’re not getting any power where you want it if you get things mixed up.

what year ecu are you running with this harness?

 

The year? Not really sure I’ll check the barcode when I get back from work it might be on there, I know it’s a p75, got a chip in it right now for 8 pounds on same non vtec setup I was running before. With the same jumper harness to go from obd2 to obd1

 

Got it, so it's an obd1 P75. So jumper harness. OBD2A or OBD2B to OBD1 jumper?

 

Really wish I knew, the car already had the ECU and jumper in it when I purchased, is there a way to tell by looking at the plugs and such.

 

Roger. Take a few detailed pictures of what you have going on in the ecu area and where the power comes in to your harness on your car. I have a strong feeling you have some parts mismatched.

- ECU
- Jumper harness, wire side and pin side on socket end (where engine harness plugs in)
- ECU connectors (B & C) on engine harness, wire side close up
- ECU connector (A) on chassis harness, wire side close up
- C131 connector, engine harness side, wire side, close up
- C101 connector (LH side of car behind shock tower), wire side of both connectors close up - chassis and engine sides

How many wires does the IACV connector have?

 

Thanks for the help so far man, as for the IACV it has 2 wires 99% sure but I haven't plugged it in yet.

As you can see there is a extra grey plug on the right of the ECU that I am not certain what it is for as my last harness didn’t have it. I will take some more photos tommorow in the am. But on another note I was thinking maybe I need a OBD2b - OBD1 jumper, because although I’m not certain but I believe my current jumper is OBD2a- OBD1.

 

C'mon OP... this is engine swap 101 stuff here. You MUST use an engine harness that matches the chassis... an OBD-2B engine harness only has two plugs on it and the third plug is the one in your photo that isn't plugged into anything. You will then need to purchase an OBD-2B -> OBD-1 jumper harness and then plug in your P75 ECU. Then all will work as you expected.

 

Yeah, that's not going to work. You need a 99-00 engine harness.

 

Yea I agree, the more I read the best option defintley seems to be just to get a OBD2b harness. Dumb decision by me, should of read more before hand, I really thought the 96-00 were all pnp

 

If you’re willing to do some work you could repin and do a little adaptation but it will cost you more than just getting the right harness. This would be the closest to ideal harness for your setup:

https://www.ebay.com/itm/2001-HONDA-....m46890.l49292