Thread: Need help. Do you have a 96-98 Civic ECU and multimeter?

I'm pretty sure I'm dealing with a fried ECU here on my brother's new Civic. Long story.

If anyone has a 1996 - 1998 Honda Civic ECU can you test for continuity between pins A11/A24 and pins D11/D12. Pins A11 and A24 are power (to ECU and injectors), and pins D11 and D12 are sensor grounds. I don't think they should be connected, but on my ECU they are. Can anyone confirm that they shouldn't be connected internally?



I'll post on Honda-Tech and see if anyone there can help but it will have to be approved by the mods over there.

If you have a 1996 - 1998 Civic and don't want to pull out the ECU to help me, just check to see if the right-side wires (yellow with black stripe) on the injectors have continuity with ground. If yours don't, then my ECU is fried.
Thanks!

http://www.sr20-forum.com/howtos/24833-free-chiltons-online.html#post359838

I have the FSM in PDF form. Chiltons nor the FSM is going to have anything that can help me. This thing has electrical gremlins like woah. The SRS unit (airbag computer) is also toast, and when I put in some "missing" fuses I think I killed the ECU too. The thing is a mess.

The yellow/black is the positive wire for the injectors. What kind of continuity are you seeing?

With the ECU plugged in and key off I'm seeing continuity like this.

Positive battery pole -> 15 Amp fuse in engine bay -> Pin 1 on main relay







Once I turn the key to the run position I get continuity like this.

Positive battery pole -> 15 Amp fuse in engine bay -> Pin 1 on main relay -> Pin 3 on main relay -> ECU Pins A11/A24, all four injectors, and ground (through the ECU it seems).
Which immediately blows the 15 Amp fuse in the engine bay.





With the key off, and the ECU connected, I've got continuity between the injector "power" wires and ground (through the ECU to the sensor grounds I believe).
Not cool.
If I disconnect the ECU I don't have continuity between the injector "power" wires and ground any longer.

Sent a text to my friend the Honda guru. Should text me back shortly.

Okay, he called me. He first asked what the mileage was, because the main relays normally shit the bed between 110K and 150K miles.

He said that he's never seen a Honda ECU go bad, unless someone's intentionally fucked with it, or didn't connect the ground harness to the thermostat housing which blew an ECU up. Your problem he said is not from that, because the car would act as if there wasn't an ECU connected at all.

Disconnecting the ECU won't help you troubleshoot according to him. The ECU is needed for the power distribution circuits. He said to pull the main relay, and replace the 15amp fuse. Switch key to run and if fuse doesn't blow, obviously the relay burnt up. The relay according to him gets very hot and over time the solder actually ends up soldering the separate plates together, which would give power where it shouldn't.

Make sense?

Sure you've probably tried that before, but just passing the info along in case you haven't yet. It'll give him a good starting point to work from.

Thanks for the help Cliff. I've read all about the main relays going bad, so that was the first thing I checked (since I wasn't getting fuel pressure). I didn't see any hairline cracks in the solder joints (which is what I'm told is the typical issue) but I re-soldered all the joints anyway just to make sure.

However, if the main relay has an issue where it's grounding out the wrong circuit it could be causing my problem. I've got the diagnostic steps to go through and check to see if it's working properly and I guess I'll have to go through them one-by-one. I did check the main 12v relay and it's working properly. I checked some of the other components on the main relay device and everything seemed fine, but I guess it's time to really check it completely.

If I pull the relay and plug in a new fuse and turn the key to run the fuse doesn't blow. But I'm not convinced that definitively means the main relay is bad. If the main relay is bad, I will find out tomorrow. That would be so much easier to deal with than a dead ECU.

I've got some other thing to test from a guy over at Honda Tech so I'll be busy tomorrow with the 30 minutes I'll have after work before the sun goes down.