Ecm is not sending a signal to trigger iac

**joegreen** · 01-09-2015

I used to be able to plug into the ecm but one day it stopped allowing me to connect. I do not have a p/n switch so it thinks its in drive all the time which works fine for me. The throttle body has been rebuilt and all the passages are clean and so it the iac. Are the voltages coming from the ecm to the iac supposed to change or should they stay constant? Is there any was for me to power the iac manually to see if it works?

**tayto** · 01-12-2015

Originally Posted by joegreen

I used to be able to plug into the ecm but one day it stopped allowing me to connect. I do not have a p/n switch so it thinks its in drive all the time which works fine for me. The throttle body has been rebuilt and all the passages are clean and so it the iac. Are the voltages coming from the ecm to the iac supposed to change or should they stay constant? Is there any was for me to power the iac manually to see if it works?

what kind of truck do you have? i had a 64 impala that i was able to use the existing neutral safety switch and a spst bosch relay to tell the ecm if it was in park or drive. let me know i can post the wiring diagram...

**joegreen** · 01-13-2015

Its a 1978 chevy k20

**joegreen** · 01-24-2015

I reinstalled windows 7 after putting a ssd into my laptop. Tomorrow i am going to retry to connect to the ecm.

**joegreen** · 02-01-2015

I have not tried to connect to the ecm yet but i think i will try tonight. It looks like i can get a 1227747 cardone ecm from advance auto for $78 (actually like $90 something but i get my $15 core charge back) shipped. So the only thing keeping me from buying this is i don't want to spend the money if i do not need a new ecm. The things that have me suspecting i need a new ecm.
1. I cannot connect to my ecm but i can connect up to my dads fine.
2. I cannot get the check engine light to work and i have tried everything. I narrowed it down to the ecm not supplying a strong enough ground to light up the cel.
3. The iac does not work and i suspect the ecm may not be sending out the proper signal to move the iac pintle. I can get 11v on two pins and like .8 on the other two but i believe they are supposed to switch to move the stepper motor, idk i might be wrong on that one?
Right now i am getting 4-5 mpg and i cannot see what the heck is going on because i cannot connect to the ecm. What would you do in this situation? Thanks

**JeepsAndGuns** · 02-01-2015

There are no junkyards around you that might have one for cheap?
It does kinda point to a bad ecm. Its to the point that if it was me, I would be plugging in a knowm good one to see if it worked.

**joegreen** · 02-01-2015

i do have a junkyard near me that would almost definitely have an ecm. I was just thinking new for the warranty and the fact that it is tested. I suppose once i solder in my chip adapter the warranty goes anyway. I just did not want an ecm with a bunch of old capacitors and whatnot. What is the lifespan of these ecm's? How much do you think a junkyard would charge? I would love to not have to fork out the money for a new ecm.

**JeepsAndGuns** · 02-01-2015

Every junkyard is different. Best bet is to call them. Also, most (not all) junkyards will give you a few days warrenty. Most around here give you 30 days.

**joegreen** · 02-02-2015

It looks like i can get a remanufactured 1227747 ecm from advance auto by cardone for $64. That is about as cheap as i can get it. Should i do the deal or see how much a used junkyard one is?

**steveo** · 02-02-2015

i'd take a working wrecker part over a reman cardone one any day, even if they're the same price.

when cardone finds the failed component, whether it be a seal in a master cylinder or a capacitor in an ecm, they will replace it with the cheapest peice of shit part they can find on alibaba so it passes the tests and they can get it out the door.

just because it's been 'remanufactured' doesn't mean it'll last as long as one from a wrecker...

**joegreen** · 02-02-2015

ok, good to know. thanks. ill check with my junkyard and see whats up.

**joegreen** · 02-04-2015

ok, its $50 plus tax for a used ecm from my junkyard. Does that seem like a good price?

**brian617** · 02-04-2015

Thats what we sell them for here at our salvage yard.

**joegreen** · 02-05-2015

Cool, thanks. I will pick one up from from the junkyard.

Now i am not certain if i have to remove the ecm from the vehicle or if they already have some removed but when i looked at my dads ecm it was buried behind the glovebox and looked difficult to remove, are their screws i need to remove or does it just pull out? What vehicle will be the easiest to remove this ecm from? Also my ecm is literally sitting in the glovebox because i don't have anywhere to mount it. I might take a look at some of the older chevys and see how they mounted the ecms. Should i look to get an ecm from a vehicle with as little miles as i can find because more miles equals more wear on the ecm or does it not matter? Lastly is there anything i should look for when choosing an ecm such as water spots or burn marks? Thanks guys.