The basics:
Chassis - 1999 Honda Civic EX Coupe
Engine - B16A2 (completely stock)
EWH - EM1 (1999 EM1)
ECU - P2T (1999 EM1)

The history:
I bought the car with a a stripped engine bay. Most of the OEM parts were missing and I have been slowly piecing everything back together. I intend to give the car to my son, and I want everything to work as if it was a stock EM1.

The mystery:
I have the engine mounted in the car and the EM1 harness mostly connected. I have 3 set of plugs that didnt obviously connect to anything.
Picture 1: three plugs that looks like they want to land somewhere on the front of the engine bay.
Plug 1 - 2 wires, red and white
Plug 2 - 2 wires, also red and white
Plug 3 - 2 wires, green and blue/yellow?
Picture 2: one plug that looks like it wants to land on the transmission. Very greasy, so maybe lower towards that CVs?
Plug 1 - 2 wires, green and purple
Picture 3: I am pretty sure this is the IAT plug, since I dont have an OEM intake tube and IAT sensor I cant tell.
Picture 4: I am pretty sure this is the Crank sensor. I will do the rewire trick and ignore this plug.

Please let me know where these other plugs should go, or if I am wrong with my assumptions about Pic 3 and 4.

Pic 1

PIc 2

Pic 3

Pic 4

 

Post wire colors for each plug in question please. You are correct for pics 3 and 4.

 

Wire colors added in original post.

 

Immediate thought is that you have an auto trans loom on a manual trans setup.

I’m not familiar enough with the auto trans pinouts to confirm but I also never seen those extra plugs on a manny loom.

Are you positive that it’s an EM1 loom? How many wires for IACV? Any markings?

 

JRCivic1 and spAdam are correct.

 

Well that sucks. Harness was on the engine when it came, so I assumed it matched the engine / trans. What are my options at this point? I assume I need a new harness, but actual EM1 harnesses seem hard to find. Would a 1999 EX MT harness work?

 

EX MT will work with minimal pulling and stretching.

Yours is likely an EX auto (assuming it has vtec wiring) - you could just do the 2 wire IACV conversion, then clip those connectors off and depin/clip the auto wires out at the ecu end to make sure they are dead headed.

99-01 CRV manual harness will fit great but requires adding 2 to 3 wires for vtec.

 

Would I need to do anything for reverse lights, etc? I saw some stuff on adding those features into an auto harness. If its just a matter of remove the extra wires/pins, I am okay with stripping the harness, removing what I dont need, and rewrapping it. Can I just chase the AT plug wires back to the ECU and remove them?

 

Engine harnesses from a '99-00 Civic for Automatic applications will have THREE ECU plugs and one green crossover plug at the cockpit end... manual versions will only have TWO ECU plugs and the green crossover plug. One additional ECU plug is part of the under-dash/chassis harness. How many do you have ?

 

There are 4 plugs on the ECU end of the harness, including the green, which I believe plugs into the chassis harness. So that confirms its an AT harness. interestingly the IAC mod is already done as the orange wire is already removed from the ECU plug and a 2 wire plug is installed on the engine side.

 

Looking at the OBD2B pinout I found online, I cant imagine how the MT would only have 2 plugs. All three plugs appear to have wires unrelated to the trans. Does the MT ecu really rearrange all of these wires into only 2 plugs?

 

No, but the 3rd plug, with necessary wires to make the engine run, is already under the dash (NOT part of the engine harness). You will need to plug the two larger plugs from the engine harness, along with the grey or blue ECU plug under the dash, into the ECU. Also, don't forget to connect the two green cross-over plugs together... one from the engine harness and the other from under the dash near the ECU. You will leave the smallest ECU plug disconnected... and I believe all of the wiring there is only auto transmission related.

 

If you look, you'll notice that all of the stuff on ECU A are chassis connections. Same with C131(Green connector).

Fun observation, it wasn't like that as much on the OBD2A ecus/looms.

 

I have a stock 00 EM1 in the garage right now (b16a2 MT OBD2 as it came from Honda). If there's any pics that would help this endeavor, just let me know.

 

First off, thank you guys so much for the help. I am sure some of these questions seem dumb, but youve been really big help. Hopefully last couple of questions. If I took the AT harness I have and I stripped out all the wires from plug A, and all the wires from the AT harness plugs that dont have a match, would I basically end up with a MT harness?

Is the extra wiring kit (https://www.c2specmotoring.com/produ...wiring-harness) for an AT to MT swap because some wires dont exist in the AT chassis harness and need to be added? Since I have an MT chassis harness I dont need to do any of this, correct?

 

Could you possibly take a picture of the engine bay under the air intake tube? I would like to see some detail on how the evap canister is connected, hoses and electrical. I also want to make sure that I have the heater hoses and wiring harness routed correctly. Thank you for your help.

 

You're in luck, I already had the intake tube off so easy pictures.

 

Thank you for the pics. Thats perfect.

 

If you have the em1 harness just plug it in .

 

apparently I dont... I thought I did, but these nice people helped me figure out I have an EX harness for an automatic..

 

You mentioned removing all of the wiring at ECU position "A"... the automatic transmission ECU plug is actually plug "D" !!! It is the SMALLEST of the four plug locations on the ECU. It seems apparent that you are not entirely comfortable with wiring, so I would NOT suggest attempting to remove all of the wiring for the "D" plug and the associated connectors in the engine bay. The safest thing for you to do is to remove all of the plugs/connectors in the engine bay around the transmission bellhousing area by snipping off the wires close to where they exit the main harness loom, tape over the bare ends of each wire, and then tape them flush to the engine harness loom. In the passenger floor board, simply zip tie the unused ECU plug "D" back toward the engine bay on the engine harness itself and you don't have to worry about it. This way, you aren't messing with any power or ground wires that are shared along the route of the wiring out to the engine bay through the engine harness.

You are really making this more difficult than it needs to be: Leave the "D" ECU plug disconnected from the ECU. If you want to clean up the unused plugs in the engine bay, do as I suggested above. If the engine doesn't run after plugging in the three remaining ECU plugs (A, B, and C), one from the under dash/chassis harness (grey) and the remaining two (one grey and one blue) from the engine harness (and connecting the two green "crossover" plugs)... something else is bad wrong.

 

Thanks for everyone's help.