[RESOLVED]Is my ECU toast?

[brownfinger]

Alright. Short version of the story first. I can't get any kind of output from my diagnostic connector. Car is unmodified 1993 2L, NT. Instead of buying a logger that I shouldn't need, I decided to try the low-tech check. I got a digital VOM a while back, and can't find my analog. I soldered a little radioshack lightbulb to 2' of speaker wire and soldered two little tiny female speaker connectors (with rubber boots) to the other end. Plug one into #1 (upper left), the other into #12(lower right). Nothing, zero, zilch. I'm sure the connectors are tight. I soldered up the rig to test for VSS output. The idle drops straight to 750-800rpm while the car is still moving. I connected one terminal to #11, the other to ground. I wasn't suprised to see no flashing there, so that's when I decided to check for stored CEL codes. When I got no response there I marched all the way around the car to the battery, the light works fine. My real trouble is a cold-start problem; the car stutters between 1000-1900rpm when cold, and it deminishes as temp builds. It runs too well to tell there's something wrong once it's hit operating temp. I had been focusing on the sensors, and their ends of the harness. Am I looking at the wrong end of the harness? Is there something I can check without yanking the ECU?

 

[GnArKiLL70]

i would pull the ecu and check it anyway. ### if it is the probem you might be able to catch it befor it gets to bad

 

[brownfinger]

if I pull it to 'check it', what am I checking for? Pop the case and look for leaky caps?, Toast-like appearances?

 

[steve]

Please don't use incandescent lights to test electronics. They can draw 100's of milliamps of current and damage the circuits your testing.

 

[brownfinger]

yeah...sort of figured that out. I tried my digi VOM, because I couldn't find the analog. It just didn't seem right that I was getting absolutely nothing. The digi did give a fluctuating voltage reading, so I tried a different light bulb-one so tiny it can hardly be seen. Grain of sand sized. I figured the other bulb, marked "extra-bright", just required too much current to operate. Now I got a code twelve. That makes sense. This morning I detached the MAF connector while the car was running. I guess it is working what are the odds that my light-bulb escapade damaged my ECU? Are LED's safer/is there a mAh limit to observe?
Anyway, I'm probably going to double-check my timing, reset my BISS, try seafoam or MCCC, reset my ECU and then see what I've got. I guess I have a little [RESOLVED]ing to add to my thread title.
Thanks Steve.

 

[steve]

Now I got a code twelve. That makes sense. This morning I detached the MAF connector while the car was running. I guess it is working what are the odds that my light-bulb escapade damaged my ECU? Are LED's safer/is there a mAh limit to observe?

If you were able to get the code for the MAF out then you didn't fry the output driver for the diagnostic data line. Most logic or transistor output can drive a LED directly (assuming the LED has the correct series resistor for the voltage levels) without any risk, I use a 12v piezo buzzer that only uses about 7ma and save me from having to watch, I can count the tones while I look at other things.