I will try to be brief . . . I have searched other posts but haven't found any that answers my questions:


2000 Blazer 4.3L 4x4 4-dr:
At sporadic times, all four lights will light up on the 4x4 panel. After a click or two from behind the dash and the 'Service 4wd' light comes on, everything will return to normal. I am not attempting to switch ranges or modes when this does this. I can still get into 2HI, 4HI, & 4LO. The problem will happen whether I'm in Auto4x4 or 2HI.

1. This will happen with both hot or cold engine. I recently went on 100 mi trip and the lights came on 10-15 times on the way there. It sat for two days, then when I started the engine it happened once, but then never came back the rest of the way home.

2. When the ignition is turned to on, everything is normal. All four LED's light up, some clicks, and the appropriate LED stays lit.

3. I have not been able to retrieve any diagnostic codes. (Where the heck is number 13 pin?? Does '00 Blazer even have a #13 pin??)

4. At times I have noticed the problem when hitting bumps, but at other times there seems to be no correlation between bumps and the lights.

5. I notice some lagging and pulling just prior to and during all four LED's being lit. Laggin/pulling goes away after reset.

6. I cannot find the TCCM to check for loose or corroded wires. Where is it located and how do I get to it?

I would appreciate any and all ideas/suggestions - Thanks.

 

I have the same vehicle that had the same exact problem. I took it to the dealer and first they told me the wiring was corroded at the TCCM. Was told if that doesn't fix it they will have to replace the TCCM. They replaced the TCCM and then told me the encoder motor needed to be replaced.After that they replaced the encoder motor they told me the pins were bent on the encoder motor connector and needed to be replaced. They replaced the wiring and supposedly its fixed. I picked up the vehicle yesterday and so far so good. The dealer had the truck for a week and payed for a rental car for last weekend and did not charge me for the labor to replace the wiring. This has been a nightmare and cost me over $1500.00 dollars. Good luck with yours and keep post back with your results.

 

Wow, not exactly the news I wanted to hear, but thanks for letting me know I'm not the only one out here with this problem. Sorry to hear you had so much trouble.

Some additional on mine:

-I'm assuming the TCCM diagnostic codes are read through the OBD-II connection, is that correct? I only have four metal pins in that connnector.

 

You have to have a scanner to pull the codes. And the Autozone scanner will not read the codes stored in the TCCM.

 

Update:

I finally figured out how to pull off the passenger kickpanel without breaking it and located the TCCM. Before I even took off the TCCM tho, I heard some clicking when I was bumping it while taking off the kickpanel. This tells me loose/bad connection.

I did have some green corrosion on two of the pins. I cleaned up the corrosion and brushed the pins, and put everything back together. Under the TCCM bracket I could see where water had gotten in, although I'm not sure how. Before I put the TCCM back on the bracket I put some plastic behind it to help shield it from any liquids; hopefully that helps.

I'll post back once I have a chance to drive it around some.

 

Sounds like a nice easy fix for you, hopefully!

Anyway, you should put some dielectric grease in the connector to prohibit corrosion from starting again and even keep water/air away from the metals in the connector.

 

I have noticed the same problem more in the hot weather, but now that it has turned cold I never encountered it . . . until tonight. Warmed the engine up and left it idling while I picked up my kid at the babysitter's house. Got back in, and all four lights were steady on. Since then the lights have been coming on, going off, and the TCCM is clicking more than ever. I tried cleaning up the connector pins on the TCCM, but didn't seem to help.

Am I looking at replacing the TCCM? You bet.

 

bump

 

Someone posted on what to do to get the TCCM to give you the codes. Something like grounding pin 13 on the DLC... Run a search and I'm sure you'll find the explaination. I don't remember it off-hand...