So I own an 89 Civic Dx with a D15B1. I yanked out the wiring harness and I did not label the sensors as I unplugged them so I forgot where some sensors plugged into. The previous owner literally hacked the wiring harness together but somehow worked without a check engine light going on. So my two main questions are, what/where is the sensor that is disconnected plug into? and what wires run to it? Any help would be much appreciated. I am a noob when it comes to wiring so please be gentle if there is already a post about this, please point me to it. I couldn't find anything that could help me out. Thanks once again for any type of help. And I apologize for the long picture descriptions, I just want to make everything clear. This is the plug that got disconnected as I pulled the harness out. (the white wire was also attached, from what it looks like to me is an extension added to the harness to make longer) What plug is this?
This a picture of the full 89 Civic DX wiring harness
This is the section where the wires are a mess.
So there are four wires. There is a red and white wire intertwined together, a solid color yellow wire, a green and white wire intertwined together, and a solid color white wire. The red and white intertwined color wire and the green and white intertwined wire are connected to a sensor with some extended wires. But that leaves two extra wires being the solid yellow and solid white wires. Where do these plug into? I have a feeling that these go to the sensor but I'm not sure if both do or just one does. Help me, please!!
And there this lonely yellow and green intertwined wire. I have no idea where this goes to. Does anyone know? It is next to a sensor connected by a solid blue colored wire and a intertwined yellow and black wire!! I think it was just hanging before I yanked out the harness.

 

1st picture Looks like lambda sensor connector but i remmeber i had one of this plugs hanging on my loom in last few crx's...

3rd picture 3 pins on right hand side- tps?

I don't really remember you have to download; Honda CRX (88)-(91) Service Manual and Electric supply also and just try to fallow etc.
Best way in my opinion is- extend these broken wires, stick loom into car and try to have look what's missing

 

Alright, I'll try to do that. Thank you @Modified EF!!

 

looks life youve come to the right place to find the answers to your questions ^_^

in the first picture the broken plug is for your one wire o2 sensor
and in the third picture in the middle left side the two gray wires
the one thats not connected to the plug is where your o2 sensor plug used to be

 

here is picture of the stock DPFI engine harness:


this is a blow-up of the area in question

First off – you should open up the harness in the area where the red arrow is pointing to in the blow-up to expose all of the wires.

Look at the blow-up picture.

Starting at the lower right you have the distributor connectors. the one on the right has (2) wires – one BLACK/YELLOW which is power to the igniter and one BLUE which is the tachometer signal.

Next to that you have a (5) wire connector with the following wire colors (see picture below for wire locations in the connector) (I suspect that some of these wires are on the far right of your picture #3) :
ORANGE – for CRANK sensor – goes to ECU pin B10
WHITE – for CRANK sensor – goes to ECU pin B12
ORANGE/BLUE – for TDC sensor – goes to ECU pin C3
WHITE/BLUE – for TDC sensor – goes to ECU pin C4
WHITE – for IGNITER – goes to ECU pins B15 & B17

Next, you have the connector for the COOLANT TEMPERATURE GAUGE – one wire which is YELLOW/GREEN – plugs into sensor on the end of the head below the distributor

Next, you have the connector for the COOLANT TEMPERATURE SENSOR for the ECU – has (2) wires – one RED/WHITE and one GREEN/WHITE – plugs into sensor on the end of the head below the distributor - I believe this is the connector in your picture #4 – see picture below for correct wire locations in the connector.

Next, you have the REVERSE (BACK-UP) LIGHTS – (2) wires – one YELLOW and one GREEN/BLACK – wires plug into the back-up light switch on the top of the transmission.

Next, you have the O2 SENSOR connector (which is the connector in your picture #1) – has one WHITE wire which connects to the BLACK wire on the O2 sensor and runs to ECU pin C16.

PLEASE NOTE – in all of this bunch of wires, you have (3) WHITE wires (O2 sensor, igniter and crank sensor) – in order to determine which wire is which you will need to run a continuity check on each to see where they end up at the ECU.

Also note that distributor and O2 sensor wires have shielding around them.