Electronic LED 4wd light flashing

[Dan Nicholas]

Hi,

I have a problem (I think) that seems to be getting progressively worse. When I switch to 4wd, my 4wd LED will flash for long periods of time (minutes). Even though it's flashing, it still seems to go into 4wd (but continues to flash).

Before, it was like "hit and miss", sometimes I'd put it into 4wd without the LED flashing. Now, it seems even if it goes to 4wd without the LED flashing, later on it will flash -> then stop -> couple minutes later start flashing...

Has anyone ran into this problem...?

Thanks

Dan

[FisHn2DMax]

Sounds like bad encoder? There is a TSB out on the Encoder. Usually you'll get a "service 4x4" message on the DIC. Mine did both the flashing lED and Service message. Dealer changed encoder and problem solved.

Have the dealer change the encoder per the TSB.

[smitheb]

I had the same problem with the flashing lights etc plus the "check engine" logo remained on for a day or so. It was all covered by warranty. Here is what the invoice listed:
Replaced K4124 sensor
Replace 12384996 motor
Repair made per # 03-04-21-001B

[Dan Nicholas]

Hi and thanks to everyone for their replies. I fixed the problem. Firstly, I forgot to mention that my truck is 1996 Silverado 6.5 Turbo.

As most people kind enough to offer advice indicated, the Encoder is definately a possible cause. I also felt I'd have to purchase a new Encoder motor ($500.00). However, before I committed to the Encoder, I tried some of the less expensive drivetrain parts that solved the problem (2 weeks without extended flashing from 4wd LED).

Unfortunately, because of time constraints I installed/fixed all the parts at once and never isolated the exact fix.

Here's what I did:

1). New 4wd Engagement Sensor (above actuator on front diff) $20.
2). New actuator $120
3). Replace corroded pin on Transfer Case wiring harness (on Transfer Case sensor??). Ok, I don't know what sensor this is on the transfer case, but I'll explain and anyone who has crawled under the same model truck will know what I'm talking about. This sensor & associate wiring harness is at the very top of the transfer case (making the hardest to access and work on). For those of you that have upgraded your 1996 actuator, this is the transfer case sensor/wiring harness that you splice the new & improved GM actuator's 3rd brown wire into (brown actuator wire spliced to transfer case harness brown wire). On the transfer case harness, the brown wire/pin was corroded. Sorry for the lack of sensor knowledge,if anyone knows the technical name for this sensor, perhaps they can let me know.

Thanks again!!

[dmaxalliTech]

The sensor on the top of the t-case you are referring to is simply a position switch, it sends the signal to the front axle via the brown wire that the t-case is in 4wl drive. IIRC the other two wires are blue and black, blue is signal in and black is ground, switch is just a plunger type and when plunged, the blue wire connects to the brown and sends voltage to command front axle engagement.