OBD0 to OBD1 SWAP

Okay, so you have done the ECU plugs and need to do the engine harness. Or maybe you want to do the engine harness first. Well, here it is. A few words first, though. First of all, SOLDER AND HEAT SHRINK ALL CONNECTIONS. DO NOT use cheap crimp connectors. They are unreliable. And since they are MUCH larger in diameter than the wire itself, they will introduce ugly bulges in the harness. They might also chafe insulation from the wires they are touching! As for soldering, it is best to use a jig to hold the wires. You can make yourself one using alligator clips (without wire, that is) screwed down to a piece of metal with holes about .5-.75 (12mm-18mm) apart. Strip the wires but DO NOT twist the strands. Put one wire in the alligator clips with the stripped end between the clips. Then put in the other piece, pushing the two bare ends together so that the individual copper strands on each wire intermesh. Then solder. This will result in a strong, reliable, very clean solder joint with no sharp protrusions that could piece the heat shrink. As for heat shrink, I recommend G&B. Unlike most other heat shrink, it gets pliable after shrinking rather than brittle. It is available at Orchard Supply Hardware and possibly Sears (Sears owns OSH).

Also, I recommend adding a plug for added wires at some place before the firewall. This will allow easier disconnection of the engine harness should you ever remove the engine. One of the engine to dash harness plugs from a CRX works fine. You can get one probably for nothing at a pick-and-pull type yard.

When adding wires, there will not be enough room in the bundle between the distributor arm of the harness and the dash harness plug on the passenger side. I recommend getting around this problem by adding another arm coming out at the base of the distributor arm, which contains all added wires. Make this arm parallel the arm going to the passenger side plug and add the plug by the passenger side plug. There is actually a place on the bracket to secure it close to where the main passenger side plug is secured.

Finally, I have done some things here that not everybody would consider (like using the tandem valve control solenoid wire for the oxygen sensor heater). It is therefore possible that this guide might not make a working engine harness if you use someone else's ECU adaptor. It is intended to be used in conjunction with my ECU plug chart.

1. Strip all plastic tubing and tape from both the DX harness and a 1992-1995 harness. This will make the job MUCH easier.

2. Injectors. Remove the entire injector 'sub harness' with the 8-wire connector from the 1992-1995 harness. Do not cut the wires yet and get all the pins (remove the non-injector related wires from the 8-wire connector, though). Sometimes the IAT plug is part of this 'sub harness'. If so, remove it, too. Place the injector plug assembly in the proper place and route the 'hot' (yellow/black) wires to the driver side plug of the engine harness. At the driver side plug, there are two yellow/black hot wires going to each DX injector. Connect one of these to the 8-wire connector and either tape the other or remove it from the plug. It doesn't matter which. Then connect the red and yellow injector wires to the red and yellow wires that go to each of the DX injectors. Run the other two wires (light blue and brown) to the passenger side*. Keep the pins intact so that you can easily add a plug. If the IAT plug is part of this assembly, simply connect the plug to the appropriate wires on the DX harness.

They are the same colors on both (red/yellow and green/white). If it is not, adjust the length to make sure it reaches. You might just want to cut it off and use the 1992-1995 plug for a cleaner appearance. Now that wasn't too bad, was it?

2. Distributor. This change is very similar to what is required in an HF/SI. Simply interchange the plugs, making sure you place the same color wires on the DX harness in the spots occupied by the same color wires on the 1992-1995 harness. There are just a couple of exceptions here. The 1992-1995 harness has a yellow/green igniter signal wire. On the DX harness, this wire is white. But it is of a larger diameter than the white wire used for the distributor sensor. The other exception is the extra two wires. These are used for the CYP sensor on 1988-1991 distributors but for the CKP sensor on 1992-1995 distributors. As I said in the other thread, you can use the wires from a 1988-1991 HF/SI harness. This harness has a nice, neat cable with a light blue shield that has both wires. Remove this wire, keeping the pins for an easy, clean install. Connect the shield of this wire (and the knock sensor wire) to a ground. You can add one if you like.

You then need to change the plug that has the distributor power and tach output. You can either cut and solder. Or you can remove the spade connectors and put them in the appropriate places on the 1992-1995 plug. Just make sure you also use the rubber seals on the wires if you go this route. It can be a little tricky to put them on the DX wires, though.

If you use an OBDII distributor, the colors are just the same. The only differences are (1) the pins will not interchange between plugs, so you MUST cut and solder, and (2) all distributor wires are on one plug.

3. Oxygen sensor. This is actually easier on a DX than an SI! Why? Because if you used my chart, you already have a wire for heater control (the orange tandem valve control solenoid wire) that is connected to the appropriate ECU pin. This wire comes about to where you need to add the oxygen sensor plug, too (at least for a B-motor). You can also use the black/yellow hot wire for the tandem valve control solenoid as a heater hot. Or you can route your own wire to the 8-wire connector. Then, of course, you just reroute the existing DX oxygen sensor wire to the same place. All you need then is a sensor ground. You can get one by connecting a green/white wire to the sensor ground junction on the arm that connects to the passenger side plug. This junction is just a little up from the arm that goes to the distributor plugs.

4. Knock sensor. You need to add a piece of shielded wire that goes from around the passenger side plug (and the ends of the CKP and injector wires you added) to the knock sensor. This wire should cone out at the base of the arm that goes to the alternator. Ground the shield. For the plug, if you do not have one, you can use an old two prong plug (similar to the IAT or CTS plug) if you have one. But you will only be using one prong. Make sure you use the right one.

5. VTEC wiring. Add the VTEC solenoid and VTEC pressure switch wires to your harness in a manner similar to the knock sensor. Route these wires up the arm of the harness of the distributor and to the front of the engine. Make sure you have enough length and that you ground the VTEC pressure switch. And route the extra wires (with pins) to the area around the passenger side plug with the other added wires.

6. TPS. On the DX, this is located around the injectors. You need to pull the plug (with wire) out of the harness and have it come out around the base of the distributor arm of the harness. Cut the wires and resolder to shorten the wires. If you use the 1988-1991 plug, be sure to interchange the outside two pins. Better yet, use the 1992-1995 plug for a cleaner look and to avoid having to interchange the pins. It is really no more difficult to do.

7. IACV. Reroute this wire to come out at the base of arm that goes to the alternator. Make sure you have enough length. Again, it might be better to just hack off the DX plug and use the 1992-1995 plug.

8. CTS. This, along with the temperature sending unit wire and reverse light wires, needs to be lengthened. Again, you might just want to use the 1992-1995 plug.

9. Oil Pressure Sending Unit. This also needs to be lengthened.

10. Coolant Thermo switch. Reroute this to the base of the arm that comes from the distributor and add the 1992-1995 style plug. Connect the yellow/green wire to the green wire and the black wire to the black wire.

11. MAP Sensor. Strictly speaking, this is not part of the engine harness. But it needs to be modified. Although it will reach without cutting and soldering, it will be tight. And it will not look too good. It would be better to lengthen the wire. For a neater appearance and easier job, use the 1992-1995 MAP sensor plug (you will only have to solder each wire once if you do it this way rather than twice if you use the DX plug).

12. Purge Valve. This is another instance where the job is easier on a DX. With an SI, one wire goes to the ECU and one ground. But on a DX, one goes to the ECU and the other is hot (just like a 1992-1995 car). All you need to do here is connect the red wire on the 1992-1995 plug to the green wire on the DX plug and the yellow/black wire on the 1992-1995 plug to the black/yellow wire on the DX plug.

13. Retape the harness. You are done now. Was that anywhere nearly as bad as you thought it would be?

[Edited by StorminMatt on 05-22-2002 at 21:59]

A lot of people would ask 'Why a DX?'. Why not? As the most unloved CRX out there, they are cheaper than either an HF or SI. They are more common than an HF. They are lighter than an SI and can be lightened to the same level as an HF of the same year (except 1989). They also tend to be in better shape than other CRX's. The bottom line: The DX is the best CRX deal out there.

But the wiring is hard, right? Not really. And if you are going with a 1992-1995 motor, it is actually easier in a lot of ways. The ECU plug change is really not much different. And since the DX engine harness is set up MUCH more like a 1992-1995 engine harness than the SI harness is, the job is really not too bad. In this post, I will deal with the ECU plug part. A couple of words first. The pin on the left is actually on the DX PLUG. NOT the 1992-1995 plug. A separate table is used after the main tables for added wires not on the DX plug. Secondly, the only numbering system for the pins I will use this time is the zigzag system used by Honda. The use of both numbering systems last time just seemed to confuse people.

A Plug:
A1 (yel) -> A2 (yel) Injector 4
A2 (blk) -> A23 (blk) Power Ground 1
A3 (yel) -> (unused) *
A4 (blk) -> A24 (blk) Power Ground 2
A5 (red) -> A3 (red) Injector 2
A6 (grn) -> A20 (red) Evaporative Purge Valve
A7 (red) -> (unused) *
A11 (blu/yel) -> A9 (grn/wht) IACV
A12 (grn/blk) -> A7 (grn/yel) Fuel Pump Control 1
A13 (yel/blk) -> A25 (yel/blk) ECU Power 1
A14 (grn/blk) -> A8 (grn/yel) Fuel Pump Control 2
A15 (yel/blk) -> B1 (yel/blk) ECU Power 2
A16 (brn/blk) -> B2 (brn/blk) Logic Ground 2
A17 (blk/yel) -> (unused)
A18 (blk/red) -> A26 (blk/red) Logic Ground 1

B Plug:
B1 (wht/grn) -> D1 (wht/blu) ECU Memory
B2 (orn) -> A6 (orn/blk) Oxygen Sensor Heater Control **
B3 (yel) -> A15 (blk/red) A/C Clutch Relay
B4 (yel/grn) -> A12 (yel/grn) Cooling Fans
B5 (wht/yel) -> A16 (wht/yel) Alternator
B6 (grn/orn) -> A13 (grn/orn) MIL (Check Engine Light)
B8 (blu/red) -> B5 (blu/red) A/C switch
B13 (blu/wht) -> B9 (blu/wht) Starter Signal
B14 (blu) -> D9 (pink) Alternator
B15 (wht) -> A21 (red/grn) Ignitor 1
B16 (yel/red) - B10 (yel/blu) VSS (Speed Sensor)
B17 (wht) -> A22 (red/grn) Ignitor 2
B19 (grn/red) -> D10 (grn/red) ELD (Electric Load Detector)
B20 (brn) -> D4 (brn) Service Check Connector ***

C Plug:
C1 (orn) -> B11 (orn) CYP P
C2 (wht) -> B12 (wht) CYP M
C3 (orn/blu) -> B13 (orn/blu) TDC P
C4 (wht/blu) -> B14 (wht/blu) TDC M
C5 (red/yel) -> D15 (red/yel) IAT (Intake Air Temperature) Sensor
C6 (red/wht) -> D13 (red/wht) CTS (Coolant Temperature Sensor)
C7 (red/blu) -> D11 (pink/blk) TPS Output
C9 (red/wht) -> (unused)
C10 (grn/wht) -> D2 (grn/wht) Brake Signal
C11 (wht) -> D17 (wht) -> MAP Output
C12 (grn/wht) -> D22 (grn/wht) Sensor Ground
C13 (yel/wht) -> D20 (yel/wht) Sensor Power
C14 (grn/wht) -> D21 (grn/wht) MAP Ground
C15 (yel/red) -> D19 (yel/grn) MAP Power
C16 (wht) -> D14 (wht) Oxygen Sensor Output

Added Wires (Pins are, of course, on 1992-1995 plugs):
A4 (orn/wht) -> VTEC Solenoid
D3 (white) -> knock sensor ****
D6 (orn/blu) -> VTEC Pressure Switch
B15 (blu/grn) -> CKP P ****
B16 (blu/yel) -> CKP M ****

* Unused injector wires. If you are making an adaptor harness, there is nothing to be concerned with. If you are cutting the old plugs and using new ones, you can tape them and set them to the side. Or you can make the connection above the split for a cleaner install.

** I specifically used the tandem valve control solenoid wire for the oxygen sensor heater control. This wire leads to just about the right place on the engine harness and is of a very similar color. It also eliminates the need to add one wire. Of course, you can just add your own wire if you prefer.

*** The service check connector is used both for timing adjustment AND checking error codes.

**** Shielded wire recommended. It is easiest to use oxygen sensor wire from an old harness for the knock sensor. Likewise, an old SI harness conveniently has a cable in a light blue shield that has both the blu/yel and blu/grn wires. Keep the pins intact on the ends, as they will be used.

[Edited by StorminMatt on 05-21-2002 at 21:13]

First off, you CANNOT use your SI injectors with a 992-1995 ECU. The SI injectors are peak-and-hold injectors and CANOT be used with an ECU that drives saturation injectors (although saturation injectors will work with a peak-and-hold ECU). So you MUST use the 1992-1995 injector plugs.

As far as changing the injector plugs, you can do this two ways. If you don't mind having the wire coming up and over the intake manifold from the distributor, you can just cut off your 1988-1991 injector plugs and solder the 1992-1995 plugs on. I would match up the colors for the wires coming from the ECU. But don't worry about the fact that 1988-1991 injectors have red/black wires on the hot side while 1992-1995 injectors have yellow/black wires on the hot side. The yellow/black wires coming from the 1992-1995 injector plugs can be soldered to the red/black wires on the harness. Next, you need to eliminate the injector resistor. Disconnecting all the red/black wires easily does this and the single yellow/black wires from the injector resistor plug. Slip these pins into the 8-wire junction on the 1992-1995 harness and you are set.

If you are looking for a cleaner, more factory appearance, you will need to reroute all wires coming up and over the intake manifold under it. This is not a problem with the injector wires, as they come from the driver's side only. But the other wires will need to be rerouted under. As far as the injector wiring, I would remove the injector wiring 'sub harness' from the 1992-1995 harness. When removing this, cut the injector wires going to the ECU (leave enough length!!) and solder them onto the 1988-1991 harness. But remove all the hot wires clear back to the 8-wire junction. Then connect the single yellow/black wire going to the injector resistor plug to a free position in the 8-wire junction. Speaking of the 8-wire junction, also run a yellow/black wire from this to the heater hot on the four-wire oxygen sensor. This is the easiest place to get a hot wire.

When checking codes, simply short the timing adjustment connector on the driver's side of the engine bay. This connector is also shorted for timing adjustments with a 1992-1995 ECU (just as with a 1988-1991 ECU). If you go by my chart, you will make the proper connection in order to do this.

by StorminMatt from CRX Resource.