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Discussion Starter · #1 ·
We recently had a lot of rain and I noticed my 2wd light blinking all the sudden. I've put the truck into and out of 4wd Hi and Low successfully with no issues. Truck drives completely fine and there are no issues. I've gone through the forums and every post I've seen is unresolved. Has anyone else solved this problem?

2006 Colorado i5 4wd.
 

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I don't speak fluent 4wd, so this is just info from the Service Manual under heading "Accessory Switch Transfer Case Mode Indicator Flashes in 2WD Mode".

Check the connectors on the transfer case for security and the terminals for condition.

Check connector C-105 for the same. C-105 is an inline connector that connects the engine harness to the body harness. It is a Black 14 pin connector with 12 wires. Two rows of 7 pins. Located near the battery. May have to dig around for it.

If you are looking for deeper diagnostics, let me know.
 

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I have no experience on Colorado 4wD. I have quite a lot of experience on GM Blazers and Jimmys. Assuming that they are similar here is what I know. A flashing 2WD light says that you have asked for a shift to 2WD but it has not completed it yet. There is a switch mounted on the front axle housing that senses when the sliding gear inside on the right front axle has moved and disengaged. BTW, the 4WD light flashing says it is waiting to engage the front axle.

So most GM I have worked on had a vacuum diaphragm that pulled a long cable to engage the sliding gear. I have seen some that were electrical. In either case disengagement was the default no vacuum or no electric position. I can not remember if the switch or wire being open is engaged or disengaged. If it is not electrical (the switch circuit), Then it is the sliding gear itself.

I have also seen where it will do this because the front differential was low on fluid. So try looking at this first.

The next common thing is the gear chewed up a bit and the gear does not slide easily. To test if it is truly disengaged, you can jack up one wheel ONLY, not two, and spin the wheel by hand. Watch the front drive shaft (transfer case to differential) to make sure that it does not turn. It should not turn when only wheel is turned by hand in 2WD, Based on this test you should be able to tell if this is an electrical or mechanical problem and proceed from there.

It should be noted that the flashing light does not always go away immediately. You might have to drive it a block or two when cold or if there is a slight bind on the shifting gear from being in 4WD.

Good Luck.
 

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Based on my personal experience when I've had a flashing 4WD light it's been a faulty 2/4 switch. It seems possible that if that switch can fail to transfer 2WD to 4WD it could also fail to transfer completely to 2WD. What colt373 describes was my problem only reversed, would lock in 2WD and not in 4WD.
 

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Discussion Starter · #5 ·
Thanks n9cv. I'll check it out. Yeah OldTime, its pretty weird man. Shifting in and out of 4wd hi/low works completely fine. Just odd its flashing in 2wd, but clearly 2wd is working just fine. It isn't stuck in 4wd. Radiator cracked the day after I posted this so I have bigger fish to fry at this point. I'll continue troubleshooting the transfer case deal. Thanks guys.
 
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