My son learned a hard lesson about snow driving (not very common here in TN) and I had to pull him out of the ditch yesterday. Pretty easy tow, nothing strenuous. However, afterwards, my truck absolutely would not go back into 4 Hi. Tried it still and in neutral, moving and in neutral....nothing. Zero ECU faults on GAP tool.

Today I've disassembled the console switch and tested it and it's working perfectly, so that's ruled out. I guess the next items are the ECU behind the battery, and the transfer case itself. However, that ECU has been quite dry, and I've kept the window cowl replaced whenever it looked like it didn't have a good seal....additionally, I thought the transfer ECU issues almost always came with fault codes, and I have none.

Any suggestions on which rabbit hole to go down next? Does the actuator motor ever just go bad on the transfer case? Any live values I can check with GAP that would lead me in a direction? This is an 05 V8 SE with about 130k miles. Thanks!

 

Check the TCM plug at the ECU then get under and check at the transfer itself, technically there is no 4H or 4L only H or L since there is no 2WD function.

 

You have switched it back to "highway" mode and not in "hill descent"

 

Sorry folks, I committed one of my own message board pet peeves and didn't update a problem with a resolution.

I ended up taking the console apart and pulling out the trim piece that has the suspension/hill descent/off road mode controls on it. Took that apart further and gently cleaned off contact points with electrical cleaner, paying particular attention to the contacts under the rubber pads under the rocker controls, and it worked just fine once I reassembled. Dunno what caused it initially---doesn't seem like an electrical part that would fail given the minimal use it gets, but who knows---maybe my wife spilled a a diet coke on the controls or something and didn't tell me. Either way, fixed now---appreciate the suggestions.

 

Will be pulling my console out and cleaning it thoroughly with alcohol to mitigate intermittent problems with similar conditions. These vehicles really don't like liquids of any kind spilled on the controls. Sort of reminds me of my driving instructor (my dad's friend) dropping his cigar ash on his 1963 Pontiac 2 door hardtop front seat and a small fire started, he never did that again...