This is kinda long but please help where you can. First I am trying to do something different here. I have a 1996 (OBD2) Accord LX that I am wanting to install a P28 into and keep it automatic (yeah I know ). Hopefully this will help others out that might want to do this). For those that don’t know, OBD2 doesn’t have a separate TCU like OBD1 does; so basically you have to split up the functions of the OBD2 computer. I have gathered that I need the TCU for a 94-95 Accord (OBD1) and an automatic P28 (unless someone can tell me that a manual P28 will supply the ‘UP/DN shift’, ‘Shift Acknowledge’, etc. signals) Actually I haven’t seen the P28 wiring (can’t find it) but I am assuming it will have these signals like the Accord ECU. I have traced the lines for my conversion harness but I have some questions before I can feel good about it. I used the 1997(I know I have a 96 but they are supposed to be the same) Accord wiring diagrams and a 1994 Accord wiring diagram. Some of these questions may seem obvious but I am trying to get confirmation, so bear with me. I will try to first reference the 97, then the 94 TCU, then the 94 ECU unless otherwise noted to try to keep down confusion. Ok here are my questions:

1. Is the ‘shift interlock system’ (94 wording) the same thing as the ‘Interlock control unit’ (97 wording)? B12 (97 ecu) seems to correspond to A18 (94 TCU not ECU) but the wording is different.

2. Does a manual P28 supply the ‘Baro out’ signal?

3. Is ‘PWR IN’ (97 A/T circuit page pin A11) the same as ‘Ignition input’ (94 TCU pin A23)? Also pin A11 is also called IGP1 (97 engine performance circuit page) and also seems to correspond to A25 (94 ECU). Is it ok to have A11 going to both A23 (TCU) and A25 (ECU)?

4. A17 seems to correspond to A22 (TCU) and A15 (ECU. Is it ok to have A17 goto both of these? (I think it is ok. It is just the A/C compressor clutch)

5. A20 (ICM1 ignition control module) corresponds to A21 (94 ECU). In the 94 wiring guide the TCU has a signal called ‘Engine spd input’ (A9) that comes from the ignition control module (ICM). There doesn’t appear to be an ‘engine spd input’ on the 97 ECU (why is this). The RPM output on the ICM only goes to the tach and the tach test connector. Is A20 (ICM1 97 ecu) the same signal as the RPM out signal from the ICM? The reason I ask is that I want to route A20 to A9 (Engine spd input on TCU) and A21 on the harness instead of splicing into the RPM out at the tach test connector? If these two (ICM1 and RPM out) are the same, again is it ok to split A20 to A9 and A21?

6. A22 (LG2) goes to ground location ‘G114 (on 97 diagram). At least I think it does; what do dotted lines mean on wiring diagrams? Continuing on; A22 corresponds to A25 (94 TCU) and B2 (’94 ECU). However, A25 goes to ground location G120 and A22 and B2 goto G114. Is it ok to tie these three together? I don’t think it is a problem since they are going to ground.

7. Same issues as 6 above involving A23 (labeled PG2 on ’97), A26 (TCU), and A24 (’94 ECU).

8. A24 (‘PWR In’ on ’97 A/T diagram and ‘IGP2’ on Engine diagram) corresponds to A24 on TCU and B1 on ’94 ECU (IGP2). The problem here is that A24 goes through location C437 (junction connector as does A24 on ’97 ECU) and the line out of C437 from the TCU is connected to ‘fuse#4’ 7.5A. Whereas A24 on the ’97 ECU looks like it goes through the PGM-FI main relay and then connects to fuse#33 and gets 15A. IS THIS OK for the TCU to get 15 amps instead of 7.5?!! I forgot to mention that this is also the case with A23 on the TCU (see number 3 above) it will be getting 15A instead of 7.5? Well thinking again it won’t really get 15A right, it will just pull what it needs?

9. C10 (VBU) corresponds to both A20 (TCU) and D1 (’94 ECU). Is it ok to splice C10 to both these locations? I think it is ok, it is battery power.

10. C18 (VSS) corresponds to D9 (TCU) and B10 (ECU). Same splice question. I think this should be ok, it’s just ‘vehicle speed sensor’.

11. C7 (SCS) corresponds to D6 (TCU) and D4 (ECU). Same splice question. I think this should be ok, it’s the service check connector.

12. D5 (BKSW) corresponds to D2 (TCU) and D2 (ECU). Same splice question. I think this should be ok, it’s just the brake switch.

Well I think that is all (like its wasn’t enough ). Hopefully, this will not only help me but maybe a select few other automatics out there.

Any and ALL opinions/ welcome (except telling me to just do the manual swap )

 

I'm curious to this procedure as well . I have a 99 accord auto . 2.3 Ulev obd2 , recently rebuild the engine , in framed . I managed to break a cheap knock sensor off in the block and can't retrieve it . Use various easy outs and every other idea . Pulling the engine is not an option . I may have a p28 on hand soon for free and was wondering if this route was the best way to get my vtec back online and get it running at peak/stock performance . Any help is appreciated !