Thanks much for the info Captain! I've found the 3 volume service manual very informative but quite difficult to navigate and find the information you're looking for. Seems like I was forever going back and forth; from one section or volume to another. You've made that task a bit easier for me now! I'll post again with any questions or to report on my progress.

And I very much appreciated your PM this morning! I sent you a reply and look forward to receiving your email.

BT

 

Hi Captain, and anyone else who may be following this thread.

Once again, I couldn't agree more with your tagline on the importance of understanding how things work in order to understand why they don't work! Since my last post, and a few other distractions, I've been "hitting the books" to better understand my Blazer's transmission control circuit. Including, as you suggested, the wiring schematics, component locator tables, in-line harness and connector diagrams. For clarity, my diagnostics to date have been based on the following schematic...



After getting the Blazer up in the air, I was still somewhat reluctant to disconnect Connector C175 for testing at the transmission as the connector and its harness appeared to be reasonably clean, secure, and undisturbed. So instead of starting there, after again testing the output side of fuse 11, I attached a test lamp to terminal G of connector C101 and unwrapped the S113 splice pack...



After turning the key to ON ENGINE OFF, I found that no amount of shaking, twisting, or massaging anything I could get my hands on between the Fuse 11 and C101 would extinguish the test lamp. This part of the circuit looked good. So, after reconnecting C101, I disconnected C175 at the transmission and attached my test lamp to a #59 drill bit inserted into terminal E of the harness side of the connector. Once again, with the Key ON ENGINE OFF my test lamp remained lit as I re-jostled everything I could get to in the engine compartment, under the dash, and under the car.

So it appears, the transmission circuit is indeed intact as I could find no intermittent shorts or opens from the ignition switch to the transmission connector. I guess that's the good news but I'm now wondering what the bad news might be. My simple, vintage Actron Scan tool cannot directly command the shift solenoids, and I don't have an extra test harness with which to proceed with the remaining steps outlined in the diagnostic flow charts associated with the individual solenoid trouble codes.

So, is it time to visit my local transmission guy and report my findings to him or is there anything else I can do myself with only a test lamp and multi-meter with which to proceed?

Because the transmission operates fine in between these intermittent limp mode incidents, my hunch was that the trouble was not inside the transmission and I was really hoping to find a loose or broken wire in the control circuit that I could repair and be done with it. Likewise many of the previous threads I've read on this problem indicate these problems often begin after opening the transmission pan for routine fluid and filter change and then something gets pinched during reassembly. Since my pan has never been off, that I know of, I thought it unlikely that an internal harness problem existed.

On the other hand, with 185K miles or so, and having never changed the transmission fluid or filters, might dirty fluid that could perhaps be carrying an excess of minute metallic particles be causing intermittent shorts in the solenoids or the transmission's internal harness? I'm also considering the possibility that the problem could be a faulty VCM?

At this point I am open to any and all suggestions and advice!
BT

 

Sounds like the pan drop is next! 187k miles, it's about time.

 

Thanks for your reply edac!

I'm thinking the same thing myself but haven't much of a clue what to do once I'm in there.

Do you have any specific recommendations? I doubt that all the shift solenoids could have failed at the same time, especially as the problem condition is still intermittent. After a few starts and stops and it seems always after sitting overnight, everything works normally again until the problem condition reoccurs.

I'm thinking also that the problem might be an intermittent fault in the VCM where, if I understand the circuit correctly, the solenoids are grounded when activated. Not sure if I have this exactly right.

I also have another intermittent problem where the ABS warning lights come on, stay lit for a while, and then go off temporarily and randomly. Best I can tell, from what I've read and experienced with while driving in this condition is described in the SM as a "Condition Latched Malfunction Response". I haven't yet dug into this ABS as it has generally been no more than a frustrating irritation but I'm now thinking it may be related to the intermittent transmission limp mode problem. Do you see any connection between these two intermittent problems that would point to something specific?

Any suggestions appreciated! BT

 

Here something I found researching the same problem on my brothers 97 ZR2,
GM truck bad ign. switch
It may save a trip to the tranny shop. Good luck, hope it helps.

 

Thanks for your reply Aurora-ak! After reading many of the same articles you probably did, i first suspected the ignition switch might be causing my problem. However, while my problem and codes show up intermittently, my testing seems to have ruled out a bad ignition switch as the cause. 1) A test lamp attached to the CLSTR fuse shows no loss of power when the SES lights up and the codes are set, and 2) My instrument panel gauges keep working throughout the malfunctioning condition. At this point I really wish the problem was a bad ignition switch as they are fairly easy to replace and be done with it.

I've been searching for an intermittent open in the voltage supply circuit 1020 without success. I'm thinking now that, rather than an intermittent power supply problem, my problem is an intermittent grounding problem. If I am not mistaken, all the grounding in the circuit takes place through the VCM. I've been hoping someone here on the forum will validate this theory and point me in the right direction to confirm or refute it.

From what I can tell from the schematic, the VCM also gets power (at least some of its power) via the CLSTR fuse and S113 through connector C4 at the VCM. However, if the problem was an interruption of power in circuit 1020 I think the unpowered VCM, even momentarily, would be causing other noticeable problems. This, to me, then places the focus on the grounding end of the individual shift solenoid circuits, either inside the transmission's interior harness, or at VCM connectors C1, C2, C3 (all of them?), or the VCM itself. Does this make sense to anyone else? If so, where should I be looking next? If not, <BG>, where should I be looking next?

BT

 

I was looking for some additional guidance on my intermittent "five code blues" problem, but then watched as my most recent questions slid down and off the page with no additional replies. Perhaps these latest questions would have been more appropriately posted in the Engine & Transmission Forum but for continuity's sake I'll try them here, once more, in my original thread.

To recap, I am fairly certain that I've ruled out a faulty ignition switch or any circuit problems between the CLSTR fuse and the 20 pin connector at the transmission. I am now ready to remove the pan and actually hoping that I'll discover a faulty 2-3 solenoid. With the problem being intermittent though, I am not sure what I may or may not discover. Once I'm inside though, I figure I might as well replace both shift solenoids but before starting, I'd like to know...


1) Could old fluid (150k+) contain sufficient metallic particles to cause intermittent shorts in a shift solenoid or perhaps at the internal harness connectors?

2) At what point, if ever, should I really consider reusing my old transmission fluid as I've read on some DIY sites?

3) Shift Solenoids - AC Delco, Delphi, Duralast??? Are they all pretty much the same? Or is a particular manufacturer recommended?

4) Filter & Gasket kits - Is any one filter or gasket type recommended over the others?

5) How do I determine if my 4L60E trans has the deep or shallow pan?

Thanks for any help! BT

 

1 - doubtful
2 - I would never consider reusing old fluid unless it was serviced recently and even then, a pan drop doesn't replace all of the fluid so I would still refill with fresh stuff.
3 - I would stay away from the cheaper stuff. In my opinion, you can't go wrong with either AC Delco or Delphi.
4 - I doubt there is much difference here although I would stay away from any brand that still supplies a cork gasket. Go with which ever one supplies a rubber gasket.
5 - You measure it. Plenty of information has been posted about this in the past. Even a quick Google search will get you the info you need.

 

Thank you Swartlkk!

I appreciate your reply! It looks like I have the deep pan on my 2002 Blazer 4.3 4x4 LS. (In case that helps anyone else)

BT

 

I couldn't effectively run a search or copy links from my phone when I replied earlier, but here's the information on shallow vs deep pan: