1986 C20 1ton dually conversion Check Engine Light

[kristian_dancer]

Hi Everyone,

I just bought this great old girl I naming Mabel:lol:

She starts great, runs good no drips or leaks, the only thing I have found is that her check engine light comes on over 50.

As soon as I stop and turn her off it goes away.
Oil pressure according to the gauge is around the 30-50psi, temp is good, she has oil and fuel makes no weird or unusual noises any idea?

What does the check engine read on a truck this old?

Oh has no cat dually exhaust from engine back can't see any o2's.

Thanks
for any help you might offer.
Kris

[pig rig]

look under the steering colume and see if there is aplace to plug a scanner in
if so swing it in to your local autoparts store and ask them to read the codes if you dont have a scanner

[kristian_dancer]

I tried that they said they only do 1996 or newer.
Nice truck by the way one day I hope Mabel will look that good!

[babyJay]

Go to another parts store.

[pig rig]

ok do this by using a paper clip conect A and B ports by shoving the clip in each hole. I cant remember if they have the letters on each side of the ports but I'm thinking its the top 2 on the right side.
once that done turn the igniton on dont start the engine the check engine light will flash and the first set of numbers will be 12 and it will do that 3 times then it will flash you a code so it will look something like this

flash-pause-flash-flash
flash-pause-flash-flash
flash-pause-flash-flash
longer pause
flash-flash-pause-flash-flash
flash-flash-pause-flash-flash
flash-flash-pause-flash-flash
longer pause
flash-pause-flash-flash
flash-pause-flash-flash
flash-pause-flash-flash

that would be code 22 then when its done flashing codes it will flash the code 12 again' then look up what ever the code is that it gave you I would just google OBD1 code ## and you'll get thousands of answers telling you the same thing
and the code 12 is letting you know the ecm is working

one other thing have a pen and paper ready because you might have multipul codes and it helps to be wrighting them down so you can double check yourself

[kristian_dancer]

Thanks I 'll try the paper clip once I find the connector

Any Idea what 5 speed manual will just bolt up to my 5.7 with the dually rear end?

Don't really need the granny gear.

I actually have two of the damn 4 speed transmissions

Kris

[kristian_dancer]

Ok I have checked no socket that I can find anywhere under or in the dash!

How do I replace it? I think I can see where it was, there are no wires hanging down it's just missing. Where does it pug into so I can find out what this damn check engine light is
?

[kristian_dancer]

Ok check engine lightis now on all the time. No obvious problems other than neededing a break job. No comuter anywhere that I can find no socket no code to read. Do have the most wobbly fuel gage and speedo on earth though. This light thing is really pissing me off and i don't want to just remove the bulb I want to know whats wrong any one got any more ideas ?
Thanks for any help Kris

[kris's66lwb]

The ecm should be behind the glove box if theres not one there you probly dont have one and therer fore will have the check engine light on if you want it off and dont have to smog it then pull th ebulb if your like cali folk then you have to fix that crap b4 smog time

[kristian_dancer]

Can anyone tell me what the check engine light on the 86 c20 is wired to, as in what can set it off.

If it's only for smog fine I will not care and remove bulb.

If its trans temp, fuel pump or oil pump or something vital I will have to start traceing wires.

There is no ecm plug that i can find under the dash i have removed most of it in the search.

There is a group of fuses all good.

The carb is electronic.

There is a sensor on the top of the manual transmission. I replaced the trans oil which was a cloudy light brown with new, light still on.

Oil pressure seems good, Temp seems ok,. runs ok, thristy as all hell but hey it's a 5.7.

Really running out of ideas.

I know the engine is a replacement but it seems to run ok. no obvious loud knocks or squeeks.

I really just don't want to be killing the truck without knowing it.