not a engine cooling fan, a ECM one.

So Im on my 3rd 777302 ECM, now all 3 even the original have burnt the board out in the same spot but it still runs fine

Original one was like that for 9-10 years, I believe the 2nd one didn't last as I used the old chips in it as after a while it to had the flash code for bad chip, but diff ones won't work.

Ohhh though I did add a big 3.5in computer cooling fan right over that area, but just to help keep the rest of it cool. Them suckers get hot quick.

3rd computer I got for free on warranty on the 2nd from rockauto.com and they were ubar helpful and cool about it.

[The 3rd computer though looks the worse in the said circled area.]

If I could maybe pin point it down, I might get a clue.
As what ever it is, I don't need it for the car to run good.
As of now what's causing it is a big mystery.


If where the computer harness plugs into the ECM is the top, the chip circled is in the top left corner on the board. Writing codes on the board says its chip U15. It doesn't look bad in the pic but the area round it is heat melted.
On the current ECM that is still workign and car is running fine, that chip is missing a chunk in its top from buring out.

But still car runs great. If I knew more id buy a 4th but pre cut the power or data paths to that chip so it doesn't over heat the area???

Or get what ever the short is figured out but no luck other ways.

 

That chip (U15) is the quad driver for the fan relay and the CCP solenoid. Two internal drivers are paralleled together for each, fan and CCP. Funny thing is, the '7302 here has that same chip showing as having been overheated. IIRC, it came out of a 2.8l Firebird.

Kinda' makes you wonder if the CCP solenoid or fan relay coil has too low of a resistance. GM did parallel two drivers together for each, so the load is higher then normal.

Anyway, pin A3 goes to the CCP solenoid. Pin D2 goes to the fan relay.

Note that the cylinder head temperature switch also ties to the fan relay. So either it or the ECM can enable the relay.

RBob.

 

You the man!!!

Well your still talking over my head, Im dumb but funny how it does have to do with the cooling fan.


The stock fan isn't even hooked up anymore.
Its there but I don't need or used it. I got it running off its own switch.
That is used maybe a 3-5 times a year as its only needed if I sit still for a while.


CCP solenoid???


cylinder head temperature, is that needed for anything but turning on the fan?
Could I unplug it and let it think its cold 24/7 with no changes to tuning?



Only thing I did find is that connector on top of the charcoal canister up front was screaming hot, must be some type of switch to open or close it off to suck fumes? N e ways I unplugged that with no effect on how it runs.

 

The cylinder head switch is just for the fan relay, nothing else. This is the one between cylinders 3 & 5 (passenger side).

CCP is the charcoal canister purge. And since you found that connector screaming hot, you found the problem. That solenoid is most likely bad. Can use a DVM and measure the resistance. It should be in the 25 - 35 ohm range? Been a while since I've measured one, so don't recall exactly.

BobR.

 

Well what do ya know, sort of why I need to stick to carb engines, I can stumble around them and get things fixed much easier, but it seems I have stumbled right into the problem but had no clue.

I just wanna be able to depend on it again and need not to worry.

I love my little V6, plenty of pep for around town and sips the gas down.
And I was real close to yanking all the computer stuff and installin a carb on it.

 

Under the exhaust header?
Or on top of the engine?

A quick look and it must be hiding from me

 

I thought it was were I mentioned. Looking at another source, it claims it is on the rear of the drivers side head. At this point I don't know, not much room for a sensor at that location. There are threads on the V6 board that claims it is in the cylinder head between two cylinders.

It will be a single wire connection. Most likely dark green with a white stripe.

RBob.

 

Again, your the man.

It is on the back side of the pass head.
single wire, green with white.

 

Hey, good that it worked out. Hopefully you can get to the bottom of the quad driver (chip U15) issue.

RBob.

 

Title edited, and I hope so.

I shouldn't smell any more hot parts.

And I hope this ECM last. But I am up for a 4th considering how burnt that chip got this time. It lost a chunk, id take a pic but I hate un-doing it once back in the dash.

 

RBob

Any clue on what's the reason behind the vapor canister pruge?
Why would it need to purge the line?

How does it do that?

I can see how the lines hook up n all connected n e ways, can't see what that thing coudl do but maybe let it vent into open air, through it?

 

The canister holds the fumes from the gas tank. Then runs them through the engine to be burned. It is emissions control of volatile hydrocarbons.

As the gas tank heats up it builds pressure. Once over a certain level (a hair less then 1 psi), the vapor control valve opens and lets the fumes into the canister. Where the charcoal holds them.

When the engine is running and in closed loop the ECM opens the CCP solenoid to allow the fumes to be purged from the canister and burned in the engine. I guess you could also say it improves fuel mileage.

ECM: the quad driver can be replaced. As long as the PCB is still OK.

RBob.

 

I got a gift card for autozone so Im gonna use that, will only cost me $30 to buy a new one, it will have a 1 yr warranty too.

THen Ill have 2 "good" ones to use, one with just a crispy U15 chip.

Still got my original as rockauto didn't ask for a core.

 

Ahhh I have been running a vented gas cap for years, its one of those cap with thew hole in it, so you don't have to remove it to fill up.

maybe it got all pissy, never building pressure.

Wonder if I could bypass that CCP so it sucks fumes all the times and be ok???

I don't even wanna try replaying it or the head temp switch and risk buring up a new ECM again, since it runs ok with out those 2 things.

 

Going over n over this in my mind before I hook up the new ECM it makes more n more sense as the other two didn't fry at first.

I would get a good 10-15 mins the first time out before I saw smoke rollin out of the ECM box. Which was when it hit closed loop once everything got wrmed up good. It then triggered that CCP and sizzle it goes.

Its real nice to know its not anything major major........


I do powder coating and some custom fab work,
if ya need anything ill do it as close to free as I can.

 

Well I changed computers and no smoke or funny smell, which just warms my heart hehehe I can trust her again.

Here is the pic of the burnt computer that still works.
Will warranty it in several months so I always have a good spare handy.
LIke to have a spare set of chips, my stock HNTs are done for, the HNLs I got used are working but Im gun shy now.