That still isn't concrete proof that the TCCM isn't at fault. The crappy part is that the rest of the proper diagnostic path pretty much requires the use of a full feature scan tool that is capable of sending and receiving information from the TCCM to diagnose further. The alternative is to get creative with a multimeter and some back probes to monitor the channel output during a requested shift.

 

Humph.
Here's a thought, what's the replacement cost of a TCCM likely to be?
Where can I find the data to do the probe tests?

 

I can't seem to get a price off of O'reilly or autozone. You would probably have to just call your local auto parts store and ask them how much it would be.

 

Hi 84BlazerS10,

O'reilly n autozone? I've not come across them.

That's easy for you to say in Oklahoma - I'm in the UK and there is only 1 source of parts - a specialist outfit located in the outskirts of London that has a link to the GM network and has parts shipped over from the US which means I end up paying at least 3x in GBP what it would cost you in USD.

Alternatively I contact US distributors directly (buyGMpartsworldwide) and have them ship it to me in UK - as I did recently to get a new Transfer Case Control dashboard switch - with about a 2wk delivery lead time I saved about 50GBP on the deal.

The Blazer is a rare beast over here, but I guess it might be worthwhile checking to see if any breakers have one in stock that might have a decent TCCM.

 

Hi , if its any consolation i have the same vehicle (99 uk blazer) with the same problem. i am upto the same point, cleaned all connections still have same prob, there is a blazer being broke on ebay if its of any use .

 

Hi Kaybo,

sorry to hear you in the same boat - frustrating isn't it?
Have you been through the BCM pain barrier yet?
How many miles has your chevy done?
Where are you located?
Thanks for the ebay tip off, I'll take a look.
Let me know how you get on with your's.

 

...so, finally got some Blazer Time (and the inclination because the temperature had at long last reached double figures!) to find the root cause of the 4WD problem last weekend. In addition it's been playing up by not starting recently when it's cold and wet - just to add insult to injury.

I had a good look underneath around the gearbox and couldn't see anything obvious out of place, in the way of damaged pipes/cables etc, so I started her up and with the engine idling and the passenger door open I pressed the 4HI and 2HI buttons alternately listening very carefully for any tell tale sounds.

I could hear the TCM clicking followed by a brief hiss, like a short intake of air being sucked somewhere which I had not heard previously with the doors shut. I repeated it standing in the passenger doorway and the noise was definitely from the passenger side, so I lifted the hood and started looking for vacuum hoses coming off the manifold/Air-intake and noted a constant hissing sound which I pinpointed coming from one of the short lengths of vacuum hose right by the ECM (?) that is mounted over the front N/S wheelarch.

Two of the short lengths of small bore rubber hose had completely perished and were allowing air to just rush in. I replaced the damaged hose lengths with some vinyl tubing I had of the same size and EUREKA I've got fully functioning AUTOTRAC again!

Such a simple fix.
I can't understand why I didn't notice the hissing sound previously!
Anyway it's sorted now - yahoo!

Thinking about it, it's possibly also been the cause of the poor starting under adverse conditions, so hopefully I've killed two birds with one stone.