1995 Accord ECU as Honda OBD1 protocol test box ?

[mr.sneezy]

I'm a guy from Adelaide, and I'm rewriting the work done by a guy on GitHub that converts Honda OBD1 DLC protocol to ELM327 protocol. His code works OK for the basics but I'm extending it.
I have the code working now on a Arduino module on a protoboard, and going via Bluetooth to my Android tablet running an OBDII gauge display app. However using my actual car as the code test bed sucks, as it's very inconvenient in Adelaide's winter weather to be out in the rain with laptops and crap hanging out the door :(

To that end I am thinking I should setup a similar bare ECU on my bench that is of the right type to be Honda OBD compatible.
I think info here on Ozhonda suggests that ECU's from a OzDM 1994 or 1995 Accord CD5 would still use Honda OBD DLC protocol like my other Honda, and so would be a cheap surrogate HOBD test ECU once powered up on the bench.
Can anyone confirm that for me before I go grab one from a wreck and try it ?
(I doubt anyone would know but hey it's free to ask :)

Thanks,
Martin

[ECU-MAN]

All pre 2000 AUDM ECU's used the DLC port. We started to see the OBDII port after the 1998 range of cars.

The popular OBDI ECU's are from the Civic and Integra range from 1992 to 1995. Although we call the next era OBDII "post 1996" they still used the DLC port and not the true OBDII port.


Good luck with your development.

[mr.sneezy]

Good to know.
I had a choice of a couple of Civic ECU's as well as Prelude, Integras and Accords (they included a P2K and a P14 ECU). In the mid nineties Civics and Prelude I could not find the DLC3 connector under the dash (which did not give me confidence) so I ended up with a POA-Q51 from a 1995 Accord. I got the ECU and loom stub plus the SCS and DLC connectors. I also buzzed out the DLC before cutting it free to make sure I know which pin it went to, and it matches data I found on the web (Russian pages).
Should have it wired up to a power supply this week hopefully and get back to the coding in comfort...

[ECU-MAN]

If the car has PGMFI and was built in 1992 or later, it will have the DLC connector.

Chances are you could not find it.

The POA ECU should do the trick.

[mr.sneezy]

I have made up a breakout board complete with five trim pots for simulating analogue inputs (ECT, IAT, MAP, O2, TPS) and I have got the ECU talking through the Arduino to Android via bluetooth OK with those dials displayed. Now I'm setting up Torque App to send Custom PID commands to the ECU to read other data like A/C, Brake switch & VTEC pressure switch.

The trouble is currently that apart from the A/C pressure switch it seems my OzDM POA ECU doesn't have a Brake switch input or a VTEC input, the wires are not fitted in connector D position 2 and 6.
Anyone know if the Brake and VTEC switch input was moved to another pin on the ECU or is there another reason there are no wires present ?
The car was an Auto so maybe they went to the TCM instead ?

[ECU-MAN]

Do the ECU connectors match the ECU ?

The ECU will get the A/C pressure switch, only A/C Switch

VTP and BKSW should go to the ECU

[mr.sneezy]

The ECU is a 37820-POA-Q51, and the most complete connector diagram and EFI wiring diagram I found so far is this one saying it's from a 37820-POA-A51, just one letter different, I found it from here. http://rusefi.com/wiki/index.php?title=Vehicle:Honda_Accord_1995
Is that far enough out for Honda ECU's to have different looms ?

The other wires were all in correct position and the correct colour codes for the main power & grounds, sensor power and grounds, analogue inputs and the SCS, DLC and Mil.
In plug D the pin 2, 3, 5, 6, 8, 10, 12 and 16 have no loom wires, which is where the info departs from my reality.

Since I posted the question above though I have got a response from the A/C pressure switch line on plug B pin 5. It took me some Googling to find out that the pressure switch is ultimately looped from the dash switch anyway, I had assumed wrongly that it was just from the gas pressure switch alone...
So I have one line working. but would appreciate your thoughts on the possible VTS and BKSW locations ?

[Dxs]

My friend is working on a 94 Accord VTi. Auto

37820-p0A-q50 is the ECU code.

If you want I can take pics of the plugs (send me a PM as I will forget this thread exists).

[mr.sneezy]

My friend is working on a 94 Accord VTi. Auto

37820-p0A-q50 is the ECU code.

If you want I can take pics of the plugs (send me a PM as I will forget this thread exists).

Yep sure, if his are not there then I guess that version missed out. IIRC the wreck I took the ECU out of still had it's Vtec engine in it. I'm going back tomorrow for some EFI sensors so I'll check again, it had an auto GB though.

[ECU-MAN]

While you are there, look to see if the engine has a VTP sensor, take photo's

[Dxs]

http://i66.tinypic.com/2e1bodt.jpg

http://i67.tinypic.com/o5oy9z.jpg


http://i65.tinypic.com/w85380.jpg


http://i66.tinypic.com/1zz6rm1.jpg

[Dxs]

Yep sure, if his are not there then I guess that version missed out. IIRC the wreck I took the ECU out of still had it's Vtec engine in it. I'm going back tomorrow for some EFI sensors so I'll check again, it had an auto GB though.

cut the plugs and take them with you.

the pics i posted is of a auto too

[mr.sneezy]

While you are there, look to see if the engine has a VTP sensor, take photo's
Bugger, I was there two hours before your post.

[mr.sneezy]

OK, yours has the VTEC wire in position D6, mine does not.
I didn't take a picture of the engine today, probably should have thought to do that, but it was yet another raining day here at the time so that's my weak excuse :)
I have the ECT and MAP plus the first 100mm of cable. Will wire up to the ECU soon. I have pressure and vacuum tool from setting up two stroke carburetors that might be able to measure the MAP output.

2974429743

[ECU-MAN]

nice work

I like the test bed :)

[Dxs]

I should also say that the wiring is from a WAGON CD Accord VTI.

I think the wagons are made in the USA? where as sedans were jap??Often certain engines do not have vtec pressure switches in one country, but they do for other counties (for example AUDM f23a engines dont have vtec pressure switches, where as the f23a in the USA do have one).

So maybe there is a difference in this regard between q50 and q51 ecu?
As discussed, as you can see in my pic, there is the Vtec Solenoid and a Vtec pressure switch (VTP). Incase you didnt know, the solenoid is the thing that opens a passage for oil to active vtec, and the VTP is basically an oil pressure sensor, so if the oil pressure is too low, then the ecu wont allow vtec to engage. If the factory setup does not have a VTP, then it just activates vtec regardless.

[mr.sneezy]

Thanks ECU-MAN, just got a better picture to post up. I responded to your PM too.

[mr.sneezy]

The test bed, now with MAP and ECT fitted. I want to fit the ECT sensor in the side of a tin can so I can test it with hot water against a thermocouple probe (to verify the Arduino scaling and offset).

29746

[mr.sneezy]

I should also say that the wiring is from a WAGON CD Accord VTI.

I think the wagons are made in the USA? where as sedans were jap??Often certain engines do not have vtec pressure switches in one country, but they do for other counties (for example AUDM f23a engines dont have vtec pressure switches, where as the f23a in the USA do have one).

So maybe there is a difference in this regard between q50 and q51 ecu?
As discussed, as you can see in my pic, there is the Vtec Solenoid and a Vtec pressure switch (VTP). Incase you didnt know, the solenoid is the thing that opens a passage for oil to active vtec, and the VTP is basically an oil pressure sensor, so if the oil pressure is too low, then the ecu wont allow vtec to engage. If the factory setup does not have a VTP, then it just activates vtec regardless.

I forgot to take a pic of the engine bay, but I did get one of the whole car and the VIN. Can the VIN be decoded to reveal the engine type/version ?
2974729748

[mr.sneezy]

Quick question for ECU-MAN. Do stock Honda MAP sensors like the one I have (PS-30) read positive (boost) as well as vacuum ?
I suspect maybe so, as I can get an increasing reading by pressuring the MAP (not much I don't want to damage it just yet).

[ECU-MAN]

I think they are good for 3 PSI, the ROM will throw a code as soon as it sees positive pressure.

That beast should have had a VTP (VTEC Pressure Switch) Its build date should be 94/95

The shop manuals graph pressure v voltage / temp v voltage for the sensors. I have added the graphs to the sensor test in the PGMFI Diagnostic DIY's I made

http://www.ozhonda.com/forum/showthread.php?67230-DIY-PGMFI-Diagnostics-Code-3-MAP