NP246 4x4 not working

[Arcee98]

Hello, my 1998 K1500 Suburban with the NP8 code and NP246 transfer case is inoperable at the moment.

I was told by the last owner the module was bad. He plugged in a new motor and still nothing. The module was unplugged and the motor removed and I had the 2Hi orange light illuminated on the switch. The truck was manually put in 2Hi. The switch also only has the 2Hi and Auto 4WD lettering illuminated with the headlights on.

I went to the junkyard and pulled an NP8 module, plugged it in, and got four clicks from it on startup. The 2Hi orange light on the switch disappeared.

Yesterday I plugged in the motor, left it loose, and still had no lights on the switch, except I had two clicks from the module this time. Pressing the buttons did nothing, no noises or lights. This was in park and neutral, running and key on engine off, all combinations I could think off.

Do I have another bad module? I’m thinking I may have a bad switch given it’s behavior and that was the only thing not touched or replaced yet. I’m going to try swapping the old module in and listen and see for changes in behavior.

 

[b454rat]

If by module you mean the computer, then yes I'd say it's bad. My Yukon had/has a bad t-case computer, no lights at all on the dash, wouldn't do anything. I took motor off t-case, heard it move once, but then nothing. Best and easiest way to fix it, swap to a manual t-case!!!! Everything will bolt up the same, just need the lever and front driveshaft, and run a wire from t-case to ECM, so it knows when in 4lo. I will be doing mine soon....

 

[GoToGuy]

Have tried looking in the service manual? See how GM would troubleshoot this? Or diagnostic logic tree. The manuals are here , search the forum.

 

[Arcee98]

Have tried looking in the service manual? See how GM would troubleshoot this? Or diagnostic logic tree. The manuals are here , search the forum.

Apparently there’s some diagnostic mode dependent on the switch lights working but I’ve got no switch light.

Any links or names of the threads you can share?

 

[GoToGuy]

Did you use the search function? " service manuals "

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Arcee98]

Did you use the search function? " service manuals "

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

Sorry I did not. Thank you very much though for linking it!

 

[Arcee98]

Well I tried getting the switch to display codes and nothing happened. Did a code clear, saw two lights for a second then disappear. Swapped TCCMs with my “bad” one and same behavior0so I pulled the switch.

Found corrosion covering the board, I’ll replace the switch as it’s only $25 and I couldn’t pull mine apart to clean it.

 

[dmhscorpion]

Well I tried getting the switch to display codes and nothing happened. Did a code clear, saw two lights for a second then disappear. Swapped TCCMs with my “bad” one and same behavior0so I pulled the switch.

Found corrosion covering the board, I’ll replace the switch as it’s only $25 and I couldn’t pull mine apart to clean it.

Often they have cold solder joints ...