1999 Blazer 4x4 ECU exchange question...

I'm looking to find out if a 1999 Blazer ECU can be replaced without having to have it reprogramed by the dealer. I bought the Blazer a year ago and the 4WD never worked and the lock converter doesn't stay locked. I've traced it to a transistor in the ECU. I bought a used, said to be good ECU off eBay. I know the newer autos need to have it programed from the factory for the correct VIN. Not sure about this one. Any chance I could damage anything by just trying it? I've been searching the internet for weeks and haven't found the answers and this looked like a good place to ask. Lot's of great info in this forum. Thanks for any help.

Brian

The lock up torque converter is controlled by the PCM, and yes, it must be programed with a bi-directional scan tool. It's extremely rare for a PCM to fail, what DTC's are you getting?

The 4WD is controlled by the Transfer Case Control Module, (TCCM) and does not need to be programed. Does the 4WD switch have 3 or 4 buttons? (selectable or auto 4WD) What DTC's are being set?

Thanks for the response, I'll have to repost the DTC, there is only one, but the 4x4 switch has 4 buttons, 4Hi,4Lo,2Hi,4Hi auto. I can get it to go into low but only 2 wheel. Every so often the Check Engine light will be off untill I'm going about 50 or so, then I'll feel the lock converter unlock and the RPM's will go up, like it just went down a gear, at that time the check engine light will come on. The other thing is when I can catch the light off, I've tried going about 5 and pressing the 4WD Hi button, that will also cause the light to come on. Would the TCCM have anything to do with the lockup converter not staying locked or is that totally controled by the PCM?

Thanks again for the great info...

....Would the TCCM have anything to do with the lockup converter not staying locked or is that totally controled by the PCM?
...

Two different problems, (not related to each other).

Only the PCM can operate the TC solenoid.