Lost My 4WD -bad shift module?

I am having problems with my wife's 4WD Tahoe and need help finding a replacement component. Thought I would post it up here and see if anyone can
help. I suspect a bad transistor in this shift control module but I can't decipher the numbers on it.

thanks , pbr333

That is probably a proprietary part number to keep people from doing the repair. Maybe an On Semiconductor part. Three terminal devices are fairly limited in scope of possibilities. Come likely possibilities are a voltage controller, dual rectifier, or transistor. If it were out of circuit, it would be relatively easy to tell between those three. Also, a good photo of both sides of the board will help to decide what the device is and/or is doing.

Before doing that, why do you thing the device is bad?

John

Are there any markings close to it on the pcb to identify it? I can see what looks like "D412" and "(R15)" which identify other components.

Read this old posting...

Well thanks for helping guys..and the replies you 3 made got me back on track ( thinking and pin to pin troubleshooting) . Initially I went through Chevrolets diagnostic procedure using factory manual , scan-tool and their diagnostic logic. This TCSC 4WD (transfer Case Shift Control) system requires repair every 50 - 100k miles since conception. Which is why all the major $ replacement parts are remanufactured , which is where I got the hint about transistors going out. I am a former master tech and always had accurate results when I went through the system pin to pin, testing in/out circiuts of the control unit (module , PCM...etc) registering the DTC's.
The DTC CO508 and the factory manual was suggesting shift module for short/open motor control but actually anything in circuit that gives a short, open ,low or high will set code. That old thread that MikeMI posted link to refreshed my brain and I went back and performed a complete test which revealed the missing voltage signal.

my complete test results = confident with the replacement part purchase.

educated guess , recommended repairs , in-circuit component testing = probable higher cost and longer delays to complete repair.

Thanks for the input everyone ...and thanks for the Forum ELECTRO-TECH !!

pbr333