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700r4 w/tbi: What tells the ECM to lock up the converter?

This GoPro is starting to really frustrate me. Took a couple pics of the service manual for you with it, but the stupid thing freezes the computer and itself when connected via USB.

IF I can get it to work, I should have some pics with better resolution.

These are in the fuel and emissions manual.
 
dyeager535 said:
This GoPro is starting to really frustrate me. Took a couple pics of the service manual for you with it, but the stupid thing freezes the computer and itself when connected via USB.

IF I can get it to work, I should have some pics with better resolution.

These are in the fuel and emissions manual.
Click to expand...

No worries!

I went to the JY and pulled a wire lead out of an ECM with a little length of wire on the end. I removed my TCC output wire, plugged in my "test wire", when scanner said "TCC Locked" I got no ground signal on my trip home (via test light and DMM).

I am guessing I should pull the ECM and inspect it? I can solder if that's the case. I am just hoping there is not a case where the ECM will say TCC Locked, but some other parameter is preventing the output signal. Seems like it should all be on the other (input) side of the circuit but who knows.
 
If testing for ground with a test light, the test light would have to be hooked to power... right?

If testing for ground with DVM that it would have to be OHMs ... right?

Or one of the ECM gounds had an issue? If it's not grounded then grounds from ECM will have no where to ground.

Have you checked the brake switch?
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There's probably nothing your going to be able to find or solder in there. If diagnosis was correct you finally found a time to replace ECM...
 
not directly related, but I had a terrible time with mine trying to pass inspection. I had no brake lights ...the wire was broke internally right at the switch: so I had voltage on one side but not the other, like it was suppose to have. the switch kept checking good. the wire was broken just past the factory crimp connector...

might be worth a look...:dunno:
 
Don't qoute me on this but I think there's 2 switches or at least 2 circuits in the brake switch.

TCC always has power and looses it when brakes are applied...
 
Yes, the test light was attached to 12v and the other lead to the TCC wire. I did a continuity test when using the DMM.

The 12v wire to the solenoid is fine and works as it should with the brakes (there are at least 2 brake switches, one for lights, one for TCC). The TCC output isn't dependent on the brake being pressed anyway (at least that's what I observed during testing).

the ECM grounds have all been tested and are fine. Besides, a chip let out the smoke. Take a look:

EA3B41B8-785D-4D4D-9063-89244AA7BB4C-1032-0000029C9BC2C549.jpg


The TCC out comes from this chip. There is an EGR solenoid and system check loop wire (A4, A5) that come out of this as well. I don't know what or when this happened, but I am surprised nothing else is broken. There was black soot all the way on the the side of the case. Do you know what this IC does?

Also, should the pathways be all crinkled like this?:

F718A6C7-03E3-484A-ACDF-3DE01FF01FE7-1032-0000029E88F930DD.jpg
 
That crinkling is normal. Smoke and melted stuff is not... :doah:

Once you let the magic smoke out they don't work after that! It's a real bitch to diagnose if you don't see the smoke come out! :haha:

First photo, above the fried chip, little to right, see the brake in circut on the board as well?

The only time I saw something like this was after welding close to a ground that was added from motor to frame in a conversion. I've accedentally welded on my rig several times without disconnecting ground and never had an issue.

Glad you found it. Don't know what caused it? :dunno:
 
By the PROM, there is another removable chip...what is it? Other pics I find show it soldered in. The guy at Oreilly says there is a charge to program the ECM, but I have the PROM so that's not necessary, right?

I have never welded on this truck before, nor have I seen any evidence of it. I had a short in the cab before from who knows what (barely acquired the burb), some 12v wires got fried and I had to overhaul some of the wiring...maybe it happened then. It seems like it blew out of pin 6, which is the TCC out. That "break" isn't a break, must be the lighting. I back probed A7 all the way to the fried chip, no open circuit. My circuit skills are rusty, is that a comparator chip? Looks like a bunch of "and" gates.

Thanks for the help.
 
The little chip next to the EPROM is the Netres or backup chip. Keep it to your new ECM.

Can't help on the rest, you've maxed out my skills...
 
It is always a good feeling fixing something, especially when no un needed parts were replaced. good job.
 
x2 :waytogo:

If that was the O2 sensor ground as well you were probably not running closed loop either, should see some MPG imnprovements as well as TCC among other things. I can't beleive it was still running like that!
 
Did you ever SMELL smoke in the cab? That's a nice one there, definitely going to say that mode of failure is pretty unusual. Glad you got it fixed though, and took the time to open the ECM up!
 
I had a 90 k1500 come in one time, that had no lockup. Figured out there was no signal from ecm at trans, but had signal at ecm. In tracing the wire, I found someone had put an inline fuse holder between the ecm and trans, and the fuse was blown. Replaced fuse, and it blew immediately. Lockup sol. was bad.

I wonder if it used to be common at all for a bad sol. to take out the ecm like that. Seems weird to me that someone added the inline fuse, but it did probably save the ecm.
 
You know, that makes sense. If the solenoid shorts, there will be 12v at the IC chip's TCC output pin. The next time the ecm sends the ground signal to lockup, BAM! it would burn the weakest part, the IC. I wonder if that happened to mine before I owned it.
 
Hello,
I have a VAN G20 6.2 Diesel 1990. The converter lock does not switch. It's the ECM that doesn't switch to ground.
I also changed the ECM with no success.
The van diesel has a MAP sensor. What is it for and where is the vacuum connected.
What is missing from the ECM that does not switch.
Please help.

Many Thanks
 
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