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OK so I was trying to see if there were any trouble codes stored in my ECU, and while i was under the dash, I could see the black single wire test connection. I could also see the green t-shaped "D-mode" connectors. But there is also a set of blue connectors (also t-shaped). What are these blue connectors for?

Also, I don't think my check engine light works and here's why: I recently returned from a road trip, and I noticed the whole trip that once I got over 55 MPH, the engine would knock like crazy, especially under WOT conditions. But the whole trip, there were no CEL or any other idiot lights. I would have thaught that with that much knocking going on, the knock sensor would have tripped the CEL on, but no.

Also when I was trying to retrieve stored codes (I followed Josh's procedure) I could never get the CEL to come on or flash or anything. This could just mean that there are no codes stored in the ECU, but with the way the car has been running, I'd be VERY surprised if nothing at all was going on that would trip my CEL on.

This is why I was asking about the blue connectors. Do they have any effect on the CEL coming on or off? Are they supposed to remain connected or disconnected? Is there any other reason why my CEL won't come on, even when the engine is having serious troubles? It's almost as if a lazy mechanic in the past disconnected the CEL somehow instead of fixing the problem that was tripping the CEL at an earlier time.

I guess my next step will be to try to run the D-check mode, since I read that if the CEL doesn't come on at all during this procedure, it is faulty and needs to be repaired.

Any thaughts on the connectors or the way my engine is behaving?

P.S. I cleaned my MAF sensor yesterday. Noticable difference in power, but I don't know if this had anything to do with the knocking above 55 MPH. Also, I replaced the knock sensor a couple of weeks ago, but I pretty much did it in the dark, my only light source being a bic lighter. I'm going to take it back off, clean the mating surfaces, and make double sure it is seated properly when I tighten the bolt.

P.P.S. If the shielded wire going from the knock sensor to the ECU were cracked or otherwise broken, could this explain why the engine was knocking so badly? I might have bent the wire (harness side) too much while replacing the KS in the dark. If this is the case, I might try the KS wire replacement mod outlined in several places on this site.

THANKS IN ADVANCE!!!

Does the CEL come on when you turn the key on pre-start? If not change the bulb...


Beyond that IHNC... haven't ever run the diagnostics...

No the CEL doesn't come on when I turn the key on pre-start. But I'm not sure if it's the bulb or a different problem. Today I did a D-check (or I tried) but the CEL didn't come on at all. I warmed the car up, turned it off, plugged in the green D-check connectors, and turned the ignition on, but instead of the CEL coming on, I just heard a relay down by the ECU clicking a bunch.

Maybe a relay down there is bad? Under the dash by the ECU, there's one white colored tray with 3 relays plugged into the top and then 4 or so other connectors plugged into the same tray. Maybe one of these relays has something to do with the CEL and is bad?

This sucks, because I thought the CEL wasn't coming on just because everything was hunky-dory. Now that I know the CEL doen't even work, I bet there's several trouble codes stored in the ECU, but I can't even find out what they are until I fix the CEL problem. CRAP.

As for the knock sensor problem, I discovered today that the previous owner of the car did replace the harness side wire for the sensor, but they didn't bother separating the shielding and grounding it seperately, they just jammed the middle KS wire into the middle of a 12 guage multi-strand wire, which they then ran into the harness. Crappy part is that when they did this, they cut the KS wire about 1/2 an inch from the connector, so I don't have enough wire to work with to splice in a ground wire. Off to the junk yard this weekend to rip one off another car with more wire to work with. But I guess that might explain a lot of the tapping and knocking coming from my engine lately.

Do any of your dash lights work?

Yeah, all the other lights work; it's just the CEL which isn't working, so I'm gonna change the bulb and see if that fixes it.

Yeah I'd start there with the bulb.

Yeah, I saw those blue connectors 2 when I was down there. Mine weren't connected, but a 93' @ the junkies was so I connected them. what they might be ihnc.

As far as cel i think u hit it. Change the bulb, then you'll be able to read codes. When i do codes something clicks by the ecu w/the key on as well, but stops once the engine is started, so I don't know that I'd worry about it.

Awesome, thanks. Yeah I've been plugging and unplugging those blue connectors periodically, and it doesn't seem to have any effect, so I'm not sure what they are. I'm about to go change the CEL bulb now; I just know that once I do, It's gonna throw a bunch of codes at me.