One last question, I promise


When I test drove this tuck, the instrument cluster was not working at that time. I has drove the blazer a good bet, and had shifted to different 4 wheel modes at will the whole test process, never once had to restart the blazer to reset. But... since the cluster wasn't working I don't know if the error was being sent to the display.


Before buying it I told them the cluster needed fixed, and they did.


After buying it there is now an issue where there is sometimes a clicking noise that sounds exactly like the flasher, goes away if you tap brakes. My research seems to indicate might need to change the signal switch or clean it.


Also there is now this 4 wheel issue.


Is it possible when they were working on the panel, there was a connection that got messed up that could be causing the 4 wheel issue?

 

The 4WD system is controlled using engine vacuum and electrical circuits. I really don't think you have a vacuum problem because 2HI, 4HI, and 4LO work as designed. There are wires in the dash for the 4WD. Mainly from the switch, (which has to be removed to remove the cluster) over to the TCCM which is located behind the passenger side kick panel. I suppose it's possible they disturbed the switch. There's a small circuit board in it that is rather fragile, and it's possible the board was damaged.

EDIT: There's a ton of things that it could be, clutch pack, encoder motor, linkage inside the transfer case, TCCM, switch, wires, etc. It's all stuff that a capable scan tool, (and technician) would/could detect.

 

Omg, sorry for all of those typos lol. On mobile.


Thanks again, just had to ask that as it seemed a bit weird that the 4 wheel mode changing was working fine before they changed the cluster and now isn't working.


I'll leave you alone now until I have it put through the tests

 

Took it into the place I bought it from this morning to have them throw it on the scanner.


He wasn't able to fully diagnose it, I need to bring it back next week, not sure what error codes he got, but I think he said he wasn't reading any speed sensor readings from the front or rear.

 

That would do it! There are speed sensors on both the front, and the rear drive shafts. Data is used in AUTO to compare the speeds of the two differentials. If the TCCM doesn't receive the data from one or both sensors, it doesn't "know" when to engage the front differential. Let us know what they find.

 

As an update, it did not correct the issue when they did a change of speed sensors.


They diagnosed farther and determined the TCCM. Changed that out this morning and problem is fixed.


Thanks again for the advice.