tonyfont

I have a 1994 SC 400. I just finished replacing the timing belt, water pump, tensioners, drive belt, primary O2 sensors, dist caps & rotors, as well as one coil pack. After repairs the yellow check engine light would no longer light up when starting the car. Occasionally (very randomly) it will “flicker” when starting the car, but it never stays on for the duration of the self test.

Some history...My check engine light has been on for about 4 months with a faulty O2 sensor. When i did the above work i also replaced both primary oxygen sensors. I figured with the amount of time the light had been on that the bulb just burned out coincidentally the same time I should have resolved the reason the light was on. Yesterday I replaced the bulb.

The Check engine light does not come on when starting the car & when jumping the E1 & T1 connector it does not flash any codes, nor do any other lights come on when jumping the connectors.

The car runs perfect 95% of the time. Sometimes when sitting at a stop light it will judder or burp. I have contributed the problem to poorer quality gasoline, I use only premium fuel however sometimes after filling up & for the duration of that tank it is really bad, next fill up, it rarely occurs. Dunno??

Occasionally when accelerating from a stop it seems to stumble & hesistate (like it is misfiring), however once I push past 2000 rpm’s it smoothes out & runs fantastic again. I do not know if the check engine light would register a misfire or some other fault when this occurs, but since the check engine light does not work I have nothing to go on.

Any help or assistance, guidance or ideas on any of the above issues would be greatly appreciated.

TechGreek

iTrader: (4)

Are you sure the light is ok? Whenever you turn your key to "ON" it should light up full brightness and then turn off.

Mine's burnt out! Another SC I was looking at the owner made sure and told me "There is no CEL" and I had to burst her bubble and say "Uh yeah, that's because it's burnt out!"

*EDIT: D'oh, check your spark plug wires. I had this issue whenever the wire from the ignition coil to the dizzy cap wasn't secured in as much as it could have been, even though it clicked and looked in there all the way*

tonyfont

Yes i am sure the bulb is OK. I just replaced it. sometimes it will just 'flicker' for a fraction of a second when starting the car. most of the time it is completely out. when i jump the T1 & E1 ports nothing on the display happens. before when i checked codes there would be 3-4 different lights that would light up & the CEL would flash the codes, now when i jump those connectors nothing lights up.

The spark plug wires were relaced a year ago & are securly in position.

93twintrbo

iTrader: (1)

Check your grounds.

masagsxr

Also another way to check it is when you put it on diagnostic mode. CEL should blink

TechGreek

iTrader: (4)

Yeah, you've got a bigger issue happening if the bulb is ok and you're not seeing it when you turn the key to on (or it flickers).

A ground should be causing everything to act funny though I would assume.

good2go

iTrader: (6)

bulb socket could be acting sketchy, like a cold solder joint, loose contact, or something

tonyfont

i do not believe it is a bulb or socket issue, as this problem started immediately after replacing timing belt, o2 sensors, and other work listed above. before i started the work it was on continually. after making repairs mentioned it would not come on at all.
???

tonyfont

Hey!! I just wanted to update this thread in case anyone else ever experiences this. Well I believe the problem was with the ECU. I was reading a thread about leaking capaciters so I decided to remove mine & inspect them. Sure enough there were a couple oozing black gunk out of them. I took the unit to a TV repair shop & asked them about replacing the capaciters...he took it in the back and came back saying there were actually 7 capaciters leaking and 1 resistor that has shorted out due to the leakage. He said there should be no problem in having them replaced. He charged me $95.00 to replace the caps & resistors...all is well now. I can also access my diag mode by jumping the connectors. On a quick test by unplugging a sensor the check engine light came right on. So...it appears i had a bad ECU that failed at the same time I did all the other work. Thank you for all your suggestions and assistance. :-)

stockhatch

iTrader: (12)

You seriously found a tv repair shop?! At any rate, glad you figured it out.

tonyfont

Yep...sure did. I took it to http://prestonvideo.com/. I figured it was nothing more than a circuit board that needed a couple components replaced...why coulnd't they handle it. It was less expensive than mailing it to a ECU repair shop...granted they could not guarantee their work, as they had no way to test it other than the electrical circuit was complete. My thought process was that if the circuit is complete...than it should work fine
:-))
which it seems to so far