legacycentral bbs

I guess the owner was told (I'm assuming by the dealer parts counter) that there are three variations of the ECU for '95. Do you think that's accurate or if it really matters?

Thanks

I think that's true but it doesn't matter; there were a few revisions over the production period but if I recall correctly they all interchange with each other.

OK... I purchased a replacement ECU before I had time to check 15 & 16 for current. Then I finally made it back over there to check and found that there is no power getting to those pins. The grounds tested ok for continuity and pin 42 had 12v, but 15 & 16 registered only millivolt variations while cranking the car. So once I received the new ECU, I crossed my fingers and tried to start the car. No change. No CEL, nothing. I double-checked the fuses under the hood and looked around (in the dark with a flashlight) at the various wire harnesses hoping to see something and while some wires looked ratty, nothing really jumped out at me. I'm going to try to get in there during daylight when I have some more time just to give it a better visual inspection to see if I see anything.

Any thoughts?

Thanks

Do any other parts of the engine management system have +12v where they should? Turn the ignition on and probe at the middle pin of the ignition coil, and at the yellow/red wires on the various solenoids and stuff.

OK, I'll check. So I'm assuming that the power source for all the FI components originates in the same place that the ECU's power originates? Like at that fuse box under the hood? And the power's not running 'through' the ECU, then to the various FI components? Just want to be sure what I'm troubleshooting here.

Not to jump ahead, but now I'm thinking that as a last ditch effort, perhaps I could splice a new wire into one of the good ones, then to pins 15 & 16? I mean, if I can't get this working myself, there's a good chance that the car will be junked.

Thanks

Yeah, I am pretty sure all of the engine management pieces get their power from the ignition relay, which is powered through fuse SBF-2.

Yes, as a last ditch effort you might be able to splice another fused source of power in to the ECU. The danger is that you're asking more of the wiring than it was meant to handle.

So this ignition relay... is that before or after SBF2?

Thanks

After. It's mounted under the dash. If you do a search for "ignition relay" with me as the author you should be able to find more info on it.

So that could be the problem then? That crossed my mind before but fell into one of the black holes never to be seen again until just now. I'll try to find your post.

Thanks

Yes, it could be the problem. Moreover, it could be the problem even if the other sensors and stuff seem okay, because it's a two-pole relay and I think the ECU gets fed from one pole and the rest of the stuff from the other pole.

Perhaps it's just optimism, but I have a feeling that's exactly what the problem is. Do you know of an easy way to test this relay? I can probably figure it out one way or another. I guess I could start by feeling for a click when the ignition is turned on and off. Or if this is the same part that's in my '98, perhaps I can just borrow that one.

Thanks

It probably is the same part that's in your 98, as well as in your 92. It's awkward to reach and remove, though. In fact, I was never able to get mine out when it went bad. Instead, I just put the new one in as well.

Checking for a click is the most basic test. But this relay does carry a lot of current and is known to eventually fail due to arcing current causing pitting at the contacts. So you'd want to look at a wiring diagram and check to make sure power's getting through the relay when it's on.

Apparently back in the 80s Subaru used platinum-coated contacts in the ignition relay, which withstood the arcing much better, but starting with the Legacy decided to forgo it.

So the relays pretty much remained in the same place over the years then? I remember going after the fuel pump relay on my '92 and almost dislocating my shoulder. Yeah, good design. I found a bunch of your posts with regards to these relays and put them in a document for future reference.

Thanks,
Dave

Yes, I think they stayed the same for a good long while. They may or may not still be the same today.

Ok, the ignition relay tested ok. That thing is indeed a pain to get to. I pulled it and it tested ok and I also verified that power is getting to it and I even bypassed it with a couple paper clips. It virtually inaccessable location limited my testing to that. It was too difficult to determine if, when on, power was actually getting to the other side of the relay when it was in place. Since I bypassed the relay and the check engine light still did not come on, I think that pretty much excludes the relay.

Now referring back to my Haynes manual schematic, next stop AT inhibitor switch? This wouldn't be the same switch that disables the starter, would it? The starter is still cranking, so that could elminate that. I don't think they would be on the same circuit though.

I did check the voltage at the coil pack. I cannot get that plug, or any other plugs under the hood of this car apart, but I was able to check the voltage of the yellow and blue wires due to damaged wire insulation. Both the blue and the yellow wires had about 1V and even tested for continuity. That doesn't seem right. Shouldn't the yellow be 12V? And I'm guessing that I shouldn't really be getting anything from the blue or red wires without the engine running.

Thanks,
Dave