Occasionally, when I'm driving my Blazer (99 LT 4WD), I'll hear a clicking sound from the passenger's side floor board. It sounds like the same click sound that the electronic 4WD system makes on startup (and also a little like the turn signal clicking sound), but it does it sometimes very rapidly. What is it? And could this be related to the "Service 4WD" light that I occasionally get? Thanks in advance for any input. I'm really hoping it's something cheap and simple that would also explain the light.

 

Does the sound stop when you press on the brakes? My guess is a bad multifunction switch. Here's a thread will a little more info: got a random clicking noise

 

No,I think it has made the sound when the car was stopped at a stoplight.

 

My '99 does the same thing. I understand it is the TCCM that's clicking. I too get the SERVICE4WD light ocassionally.I wait for it to click a bit then shut off and re-start the truck. This almost always turns off the light and enables me to use 4wd. I have also been told that the remedy may be as simple as disconnecting the TCCM and cleaning the connections.

I intend to try cleaning mine in the next week or so. I

 

That's kind of what I suspected it was (I have the same deal with 4WD working fine after a restart). How can I get to the TCCM? I've never done any work on the Blazer - my mechanical expertise is in 300ZX's and I don't want to mess anything up.

 

It's right behind the glovebox. Empty your glovebox and drop it forward. The TCCM is right there on the firewall if I remember correctly. Took a look at mine briefly when it first started clicking but was a while ago.

 

Thank you very much. I may clean the connectors just to be sure, but I'm now believing that it's the turn signal making the noise. Just this afternoon the clicking was starting with the turn signal - I'd have the signal on, turn, and then the signal itself would go off but the clicking (at the turn signal rate) would continue. Additionally, if I wiggle the turn signal arm, I can make the clicking noise without the turn signal turning on.

Thanks a lot for the responses guys.