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Username Post: 4L80E TCC Solenoid Problems        (Topic#348250)
stumppuller 
"7th Year" Gold Supporting Member
Posts: 814
stumppuller
Loc: Canada
Reg: 11-01-04
12-07-17 05:19 PM - Post#2717226    
    In response to hawk1122

Checking the PCM grounds is a good idea, but I would replace the PROM before everything else. If the PCM was damaged, there is a good chance the PROM was too. When electronics is damaged, it can do really weird things.

Also, the PCM provides the ground to the transmission solenoids. This is how it switches them on/off. The solenoids are always powered from the fuse panel from the ignition switch feeds.

Note - The removable chip from the PCM is called the MEMCAL. It's the blue assembly containing both the PROM and Knock sensor chip on the same board. The PROM chip is actually soldered to this board.

Here's the ground diagrams for a 1994.

Attachment: PCM_Ground_Distrubution.jpg (228.04 KB) 10 View(s)




Attachment: Engine_Bay_Grounds_Page_1.jpg (247.7 KB) 3 View(s)




Attachment: Engine_Bay_Grounds_Page_2.jpg (263.9 KB) 7 View(s)




Attachment: Engine_Bay_Grounds_Page_3.jpg (291.67 KB) 8 View(s)




Attachment: Engine_Bay_Grounds_Page_4.jpg (277.16 KB) 4 View(s)




-91 Sierra C2500, now K2500
-81 Chev K20


 
Low priced Genuine GM Auto Parts
stumppuller 
"7th Year" Gold Supporting Member
Posts: 814
stumppuller
Loc: Canada
Reg: 11-01-04
12-07-17 05:21 PM - Post#2717227    
    In response to stumppuller

And a few more...

Attachment: Instrument_Panel_Ground.jpg (239.4 KB) 3 View(s)




Attachment: Taillight_and_Trailer_Grounds.jpg (259.58 KB) 3 View(s)




-91 Sierra C2500, now K2500
-81 Chev K20


 
hawk1122 
Forum Newbie
Posts: 26

Reg: 10-01-17
12-07-17 06:19 PM - Post#2717237    
    In response to stumppuller

Thanks I appreciate it. That's why I really do think it is the whole computer setup, or a bad ground/wire. I'm pretty sure solenoids don't partially work sometimes, they either do or don't. I have the new PCM as I said already tested it and you know what happened. The new PROM should be here in 2-3 days. Right now I put back the old PCM and PROM just so I can move it around if needed and not to possibly screw up the new PCM.



Edited by hawk1122 on 12-07-17 06:25 PM. Reason for edit: No reason given.

 
hawk1122 
Forum Newbie
Posts: 26

Reg: 10-01-17
12-07-17 06:41 PM - Post#2717239    
    In response to hawk1122

Checked the 2 main grounds for the Tran Solenoids (G108 and 109) they look fine saw a little bit of a red hue on them. I'm gonna take them off tomorrow and clean them up also trace those wires down.



 
65_Impala 
Very Senior Member
Posts: 3928

Reg: 12-29-02
12-08-17 11:38 AM - Post#2717324    
    In response to hawk1122

I doubt it's the memcal. It contains a memory chip holding the program the processor runs. There is protection to protect against this memory chip being corrupted. There is a checksum that must match ensuring the data hasn't changed, and even if you get past the checksum the processor would crash trying to run a corrupt program. The processor hasn't crashed if you are datalogging and don't lose the connection. The CEL typically also flashes continually when it crashes and goes to the hard coded limp mode too.



 
hawk1122 
Forum Newbie
Posts: 26

Reg: 10-01-17
12-09-17 01:21 PM - Post#2717418    
    In response to 65_Impala

I got the new chip today they sent the wrong one so I’m returning it. Instead of getting right one I’m gonna get my money back. I plowed with it today it was as fine but the truck was probably off like twice out of the whole day so really no true testing there. I think I’m just going to go for the solenoid replacements first this time. No idea though checked all the other ground they were fine. Other than that I’m practically back at square one again. I really want to stick this truck through, but I’m starting to put too much money into this and getting no results. I’m gonna have to set a deadline by next month if it’s not fixed, I’m gonna plow with it rest of the season then probably sell it as is.



Edited by hawk1122 on 12-09-17 01:23 PM. Reason for edit: No reason given.

 
Low priced Genuine GM Auto Parts
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