ecu location and codes

[l75eya]

Could anybody tell me where the ecu is in an 87 hatch, and how I can put it into diagnostic mode? I had a nissan that had a small screw on the ecu and if it was turned in one direction it would throw the ecu into diag. mode and blink out the code number in the dash, is there a way to do that with these cars too, or do I have to go out and buy a diag. tool to hook up to it?

[forrest89sei]

1.5 Seconds using the search and I had this:


How to check your ECU codes:
1. move driver seat all the way forward.
2. locate the box on the floor.
3. locate the small plastic window and pop it open.
4. turn the ignition on.
5. count how many times the light blinks.
6. refer to the table below.

ECU CODES for 86-89 accord and 85-89 prelude

Ok I think we finally got this fixed now.. These are the correct codes..

00 LED FLASH(s) ECU

01 LED FLASH(s) 85-98 Accord
Oxygen Sensor "A" (Primary)
defective circuit or unplugged / defective sensor

02 LED FLASH(s) 85-89 Accord
Oxygen Sensor "B"
defective circuit or unplugged / defective sensor

03 LED FLASH(s) 85-98 Accord
MAP Sensor (Manifold Absolute Pressure)
defective circuit or unplugged / defective sensor

04 LED FLASH(s) Crank Angle

05 LED FLASH(s) 85-98 * Accord
MAP Sensor (Manifold Absolute Pressure)
mechanical problem / disconnected piping
* exc. 94-95

06 LED FLASH(s) 85-98 Accord
ECT Sensor (Engine Coolant Temperature)
defective circuit or unplugged / defective sensor

07 LED FLASH(s) 85-98 Accord
TP Sensor (Throttle Position)
defective circuit or unplugged / defective sensor

08 LED FLASH(s) 85-98 Accord
TDC Sensor (Top Dead Center)
defective circuit or unplugged / defective sensor

09* LED FLASH(s) 85-98** Accord
CYP Sensor (Cylinder)
defective circuit or unplugged / defective sensor
* not a valid code for any throttle body injection Hondas
** not a valid code for V-6 engines

10 LED FLASH(s) 85-98 Accord
IAT Sensor (Intake Air Temperature)
defective circuit or unplugged / defective sensor

12 LED FLASH(s) 85-98 Accord
EGR Lift Sensor (Exhaust Gas Recirculation)
defective circuit or unplugged / defective sensor

13 LED FLASH(s) 85-98 Accord
BARO Sensor (Atmospheric Pressure)
defective circuit or unplugged / defective sensor

14 LED FLASH(s) 88-98 Accord
IAC Valve (Idle Air Control)
defective circuit or unplugged / defective sensor
IAC VALVE HELP

15 LED FLASH(s) Ignition output signal

16 LED FLASH(s) fuel injector

17 LED FLASH(s) 88-98 Accord
VSS (Vehicle Speed Sensor)
defective circuit or unplugged / defective sensor

[greentee76]

DX? Carbed?
If you are carbed there is no onboad diagnostic.

[l75eya]

1.5 Seconds using the search and I had this:

Figures, I spent about 15 minutes trying to find anything and looked through each "How-to" sub-forum to no avail, nonetheless, thank you very much for posting that for me = ).

[l75eya]

DX? Carbed?
If you are carbed there is no onboad diagnostic.

Does this mean that there's no blinking light on the ecu itself under the driver's seat as there is said to be in the how to? I ran out and popped the little cap down and turned the ignition on and couldn't see any lights blinking in that box or anything. Do you think if the ECU were not functional at all, my car would still run? My driver's side floor got flooded and since then the car has been running like shit.

[nfs480]

If you have the DX trim then your car doesn't have an ECU at all. That's because you have the carbureted version of the engine and not the fuel-injected.

[forrest89sei]

Well the DX has a ECU, it's just not like the ECU a EFI Accord has.

If your ECU is messed up let me know, I have a working one for sale

[l75eya]

If you have the DX trim then your car doesn't have an ECU at all. That's because you have the carbureted version of the engine and not the fuel-injected.

Shit, so that gray box that's under my driver's side seat is just empty? Is there anything in that thing that affects the engine because I've been clueless as to why my car has been running like hell and this was my first break as to an idea what happened =(

[forrest89sei]

Shit, so that gray box that's under my driver's side seat is just empty? Is there anything in that thing that affects the engine because I've been clueless as to why my car has been running like hell and this was my first break as to an idea what happened =(

It's not empty, it runs solenoids and other things related to the carb on these cars, Unlike the EFI ECU it doesn't have a diagnostic mode

[l75eya]

It's not empty, it runs solenoids and other things related to the carb on these cars, Unlike the EFI ECU it doesn't have a diagnostic mode

So it's safe to say that if this big gray box under my seat happened to get....really wet due to driving in heavy rain for over an hour on the highway with a big ass hole in the rear-driver's side wheel well that led to there being about 3 - 4 inches of water on the floor in the back, that could possibly be the reason my car is running horribly and won't idle and whatnot?

I'm getting the feeling that this is probably the problem but just for a reality check, I'd really like to have it all spelled out nice and clear to be confirmed, because it's been over a week of messing around with the idle, air/fuel, vacuum advance, etc, etc and it's been driving me crazy.
Wanna say thanks a lot for the feedback as well, I've been reading on this forum for months and just recently posted a first thread, I've found tons of insightful info on here! 3g ftw!
Thx

[greentee76]

I was trying to find a writeup that lostforawhile did on this but can't seem to find it. SO I will try my best to explain the theory of how this system works.
First of all Honda set up the carb to run rich as a base. The solenoid control unit(under the drivers seat) take electrical readings and open and close solenoids on the intake manifold(white saucer looking deals) to lean out the mixture when appropriate. If the box under the seat is bad generally you will revert to a rich situation.
The best source of info on the feedback carb system that I have found (recommended by lostforawile) is chilton book # 6980 Honda 1973 to 1988.
Hope this info is helpful.
By the way if you do decide you need a new box I would take Forrest up on his, I have alot of his parts on my car now, and he is great to deal with.
Good luck!

[greentee76]

Just to clarify:
The big grey box you see under the seat is just a cover the solenoid control lives under it.