Dead ecu or ?
 

got a 1992 civic ex auto, thing is running ok but not as good as i think it should be. i tried jumping the ecu to check the timing and it would not work (paper clip in the two pin connector). the cel comes on when i turn the key to on but not starting the car, when i turn key fully the cel turns off immediately. i think its supposed to stay on for a few seconds normally? not sure.

i read if you get no cel codes at all your ecu is dead? what else can i do to check ecu?

i opened the ecu up, no fried circuits or anything, so not sure what it could be... the ecu in it now is from a 1995 ex auto, so someone changed the original out at some point.

i even tried disconnecting the o2 sensor and still no cel but i only did this for a few seconds... maybe it takes more time for cel to show.

is there another way to jump the ecu so i can set timing? :eat_arrow:

Re: Dead ecu or ?
 

Ha, no.
No fault codes means no fault codes.


You were on the right track, but pick a different sensor....

Disconnect TPS or ECT while it's running and wait for the check engine light to come on. Then you should be able to retrieve an appropriate code for the item you unplugged.

And...this only proves that it can detect and store a fault code.

What makes you say it would not work?
What did you see/hear/feel/smell/taste? LOL

Once correctly set, distributor timing should never ever change on its own.
If you discover timing is wrong, look for everything else that could possibly cause it before you try to put a wrench on the dist bolts. (Assuming this dist was timed correctly when it was installed.)
Like if the timing belt jumped a tooth, the dist (ignition timing) will appear to be 10-20 degrees off spec....and adjusting the dist can't correct that.

Re: Dead ecu or ?
 

Thanks for the reply. According to several write-ups on how to adjust timing when you jump the ECU with a paperclip or something the Cel is supposed to be solid lit up. My car is not doing this. I thought maybe the jumper I was using wasn't working so I tried others and still to no avail. Also according to other articles when disconnecting the O2 sensor the Cel is supposed to light up after some driving. My car's not doing this. This is leading me to believe mine ECU is not working properly. But I will try the other methods you have mentioned to throw cel.

Re: Dead ecu or ?
 

You wrote "a few seconds", that's not 'after some driving'.

A few seconds is not long enough to trip a fault code for that particular sensor.....but that may be sufficient time to set a code for the other two sensors I mentioned.


Maybe you should go ahead and use your timing light....see if the timing is stabilized while the SCS connector has the paper clip in it. (If it's not working right, the timing mark would be bouncing all over the place, not at all steady.)

Wait wait wait a minute!
Something I did not read in your posts:
You said the ECM shows no fault codes......but is the check engine light staying on while the engine is running?

Re: Dead ecu or ?
 

Yes i initially dis the o2 for a short time. Now ive dis o2 for an hour of driving with cel.

The timing marker is faint but seems to only show intermitantly. I need to exsentuate the mark for better viewing. However if the mark i can see is acurate in someway, it is very off. The mark apears to be set too close to the front bumper if that makes sense.

no cel with normal oporation i cant get a cel at all, thats the strange part.

i should get a cel when i jump it correct?

Re: Dead ecu or ?
 

So I disconnected the stuff you mentioned and it ran poorly meaning I have to keep my foot on the gas or it cuts out. But still no cel. Is there any other thing it could be besides the ECU?

Re: Dead ecu or ?
 

Ok....if you can force a fault code to set in the ECM,
and you can jump the SCS (2 pin connector) to make the ECM flash out the fault code for the item you disconnected,
then the SCS is doing its job for the ECM.


A little light colored paint or chalk or crayon helps to see the timing mark, but make sure you are using the correct mark on the pulley first.
The single notch is TDC (originally white), the group of 3 notches are timing targets, center notch (red) is the center of the spec range.


Distributor position (stock), regarding the location of the bolts in relation to the adjustment slots, the bolts are usually pretty close to centered in the slots. Not always, but usually.

If ignition timing light check shows a good 10 degrees off or greater, I would take the top timing cover off and check if the TDC and cam gear marks align correctly (maybe the timing belt jumped)

Re: Dead ecu or ?
 

wait, I thought you said the CEL came on while the O2 sensor was disconnected?

Re: Dead ecu or ?
 

Do you have another ECM to try?

Re: Dead ecu or ?
 

im sorry, i ment no cel while driving no o2 for an hour.

Re: Dead ecu or ?
 

i was curious about the bolts. Thank you. Ill do a check of the tdc when i get home. I think the main issue is the ecu however.

Re: Dead ecu or ?
 

Could someone before you have rewired the check engine light so it's not connected to the ECM anymore? (people might do this because they can't actually fix the real problem, or maybe so you can't tell it's broken right away and will buy the car)

When you start the engine......Does the CEL always go out at the EXACT moment the oil light or the charging light turns off? (pay close attention, possible clue!)

If I suspected it's hacked, I would locate ECM terminal A13 (grn/org wire, check service manual) and use a jumper to ground the wire, turn key to ON, check engine light should be on. Remove ground jumper from ECM connector and CEL should go out. This should prove the ECM is in control of the light, not something else.

Right now all I have is service manual info to go by.
It's probably been more than a decade since I had to use the SCS jumper method on a car this old, I don't remember specifically how the CEL acts under each possible condition other than flashing out stored fault codes.

Re: Dead ecu or ?
 

Yes the cel turns off at the same time as the oil light. From what i can gather this car has no hax of the cel. I will try your method when i get home but i suspect its unlikely there is fowl play. That being typed i do feel this condition is unique as there are no reports online that i can find.

As you sugested i will try to find another ecu to cross ref, if conditions are static then maybe your right there is a hax. Strange pattern here but with some due diligence i feel an answer is within reach. Thanks for your help :)

Re: Dead ecu or ?
 

Hmmm....if you leave the key on and go disconnect the oil pressure switch on the engine, would that turn off both lights?
Might be quicker than pulling the ECM and fumbling with its wiring, or at least that would let you know if it really is connected to the oil light circuit-- and you need to go deeper.
Got a buddy with a similar car that works right? Compare how its light acts..

Or maybe someone with an older 5th gen car can chime in with first hand info

Re: Dead ecu or ?
 

I pulled all the sensors i could see under the hood with no cel... gotta be an ecu issue. The the car runs okay but sluggish at acceleration and I'm losing MPG so I think it's in default mode limp mode or something. That's the only thing I can think of or from what I've read that seems to be the case

Re: Dead ecu or ?
 

The oil pressure switch was right next to the oil filter....I thought you'd know or ask before just disconnecting random stuff.

Now I really want to know what is controlling the check engine light.

If someone rewired the check engine light so the ECM cannot control it, then the ECM cannot turn on the check engine light when it sees a problem, and you will never be able to get the flash code readout to fix the problem.

Replacing the ECM can't unhack someones wiring hack.

Comprende?
Good.

CEL stayed on until you start the car, right? That's the only time you see it on, right?
Unplug the ECM completely ..... then turn key on and see if the check engine light stays on.

Re: Dead ecu or ?
 

ill try unplugging the ecu for a cel but i doubt someone rewired a bypass

i unpluged the o2, iac, and tb sensors, that should have been enough for a cel for sure but no dice.

ill keep you posted. thank you

Re: Dead ecu or ?
 

WOw it seems like you did everything there is to do bro. GOOD LUCK. Hope you could fix your problem

Re: Dead ecu or ?
 

so i installed another ecu that has been tested to work properly and i still cant get the cel to turn on after the initial start up... no sensors i disconnect will throw the cel.

it still runs laggy and bad mpg 25 at best on the freeway..

it does run even more poorly when i unplug tps iac however...

any ideas?

Re: Dead ecu or ?
 

Go back through this thread and see if you can complete any of the other checks I tried to get you to do to confirm the CEL is not actually operated by the ECM and someone has hacked the wiring to make it this way.

Re: Dead ecu or ?
 

I disconnected the oil pressure switch and no static cel. also I unplugged the evil, it will not start obviously so can't check for a cel... If someone hacked the cel wouldn't they have to do it threw the ecu? I thought all cel activity was managed via ecu... I'm super stumped

Re: Dead ecu or ?
 

there is a MILE OF WIRES between the ECM and the idiot light.

I can make a light bulb do just about anydamnthing I want it to do, no engine ECM involved.

Re: Dead ecu or ?
 

OK so how do I track it down-and find the solution

Re: Dead ecu or ?
 

I wrote out some things in posts 12, 14, 16, you would need to figure out how to check these.