boneychill

My short version is this? I want to replace my ECM. Engine runs fine. it does pass smog but the engine light is on, so they fail it. A mechanic told me I should replace it. I have a replacement with the same serial numbers. I am afraid that if I need to put my original one back in that it wont work. I remember reading somewhere they dont always take.

So long version here

2 years ago I replaced my head gaskets. I'm not a mechanic, but if I have the recipe or FSM I have the aptitude. I have 11,000 on the rebuild and no leaky and runs strong.(Am I right that the head bolts do not need re-tourqing? They are the kind you torque down to spec torque but one last step is you 1/4 turn all the head bolts. Just want to make sure.)
Anyways, a few months ago it was doing weird electrical things, like left turn signal stayed on and no blinking. right signal did not work. Sometimes it would just keep turning over but not start. Spark issue. A bunch of weird things. So I took it to a mechanic and spent 160 dollars just so he could tell me I need a new one. I kept pestering him about it and he finally magically made the thing run again as if nothing was wrong. The problem with that was that the engine light was now on. I did not care about that until i went to get my engine smogged here in california. My smog parameters were all good and passing but because the engine light is on they have to fail it until fixed.

So back to my question. I dont want to get into this replacement until I'm sure I know what I am getting into. Is there a chance my now-working-but-engine-light-on-ECM will not work if I try to put it back in?...in the case that the replacement one doesnt work?...do they always need re-flashing?...

Incidentally, I did find this thread https://www.yotatech.com/forums/f116...20/index2.html but it didnt really help me for my case since i dont want to mod I just want to interchange

I could not have done my head gaskets without it. Love it.

Thanks a bunch for reading and taking your time to help me.

j2the-e

No you dont retorque those head bolts.
You can plug and unplug as many ecus in that truck as you want. It will not matter. There is no re-flashing required. Just make sure the part # is the same. But I highly doubt it will fix your truck anyway. What is the code? Why not just clear it and then take it in for emissions? Does it come right back on?

boneychill

I dont know how to reset it. I didnt know you could do that. I just dont know much about the electronics of the truck, besides what I dealt with while doing the head gaskets. I replaced all of the fuel injector leads, and dealt with some of the wiring harness. I know nothing about the brains though.
Thanks for your time. I really appreciate it. I'll look inside this replacement one I have and see if I can recognize anything that looks like a reset button. I wont do anything until you or someone gets back to me.

Oh. I havent ever checked the code because the mechanic told me it could not be fixed that I just needed a new one. originally there was no engine light on even though it was doing strange elctrical things. I assume the mechanic did an over ride if that is possible, so that it would run again for me. Or some kind of trick he knows of. I guess I should buy a coder if reset doesnt work
thanks again

Cyberman

You reset the computer by disconnecting the battery.

Search on here for checking codes before you swap the computer.

Your mechanic doesn't seem to be too bright.

j2the-e

Yes, definitely pull codes first. Disconnecting battery works, but you can also pull the EFI fuse to clear the codes and avoid losing your radio station presets

scope103

Man! How someone can replace a head gasket without even glancing at the Service Manual is just beyond me....

Here ya go: http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf The "Special Service Tool" is a paperclip.

It IS possible for a failed ECU to leave the CEL (Check Engine Light) on with no underlying code, but I believe that is the LEAST likely possibility.

boneychill

hehe. You dont happen to have a part number for that specdial paper clip do you.

Hey!! I said I had the shop manual to do the head gasket. Of course i didnt just wing it. that would be impossible without having done it a few times.(Which i have not) No way would I attemp it without the recipe (instructions). This site was instrumental too, along with google.

Anywho

I got two codes. 7 blinks. which is throttle position sensor. Maybe I didnt connect the throttle cable back exactly right. The other is 1 blink which is "normal condition" or whatever. Welll that doesnt seem so scary.
Here are the two links that helped me just in case someone finds their way to this thread and was looking for the pre 96 toyota diagnostic codes.

http://www.troublecodes.net/Toyota/
https://www.yotatech.com/forums/f116...g-3vze-257428/

Thanks for your time people.
Thanks goes out to all you veterans that keep our country safe on this day of mourning
Peace

scope103

Single digit diagnostic codes were only used (I think) sometime in the 80s. I assumed you had a '94, which definitely has only two-digit codes.

My first guess is your "7" and "1" is a 71, but that only applies to a California vehicle. (Which is will say clearly on the sticker under the hood, if that's what you've got.) The path to follow is given in the manual, just follow the link.

boneychill

so I think you are definitely right scope103. i didnt read the directions correctly. If it is 71 (and not 7 and 1) then it is the Gas recirculation(EGR). And not the Throttle Position Sensor.

Maybe that is why i noticed the engine light off one time, some time ago before, because I did some work on the truck and had the battery disconnected for more than 5 minutes

The light comes back on after about 30-50miles.

But, since I was able to get the light to go off long enough to get a smog, I was able to pass the smog test, even though there is something going on with the EGR.

So the moral of the story is, if you want to pass smog in california and your engine light is on. Just reset it and make sure you are close enough to the smog shop that it wont go on again until after the test.

:0) I think we can close this thread. I have my tags and that is all i care about

boneychill

I need to correct that last statement.

If you are pre 96 vehicle you are obd-1. Which means you have the old style computer that uses the paperclip to jump the connectors......

You only have to reset the computer and take your truck or car in to get smogged before the engine light comes on again.
I'm not sure if it works for all vehicles, but it worked for my 94 SR5 3.0 3vze.
The engine light is on again and I dont care. In 2 years when i have to get smog again I know what to do.

205,000 miles and still going strong. Toyota engines are great. Even the 3.slow(3.0)

Side note: I'm having my clutch done today. $500 for clutch assembly, main rear engine seal, and starter. I paid for the parts. Just labor. $500. Is that a good deal? It seems like it. I wish i had the lift to do the clutch. I'm too old to do it from the ground. Because I could do it all myself. but a man is only as good as his tools. And I dont have a lift.