99 S10 when I hit a bump in the road the Service 4WD light comes on
goes off when restart engine
any ideas

 

Any Ideas on the service 4WD light

 

Is there any active codes?

 

You will need to find someone with a full feature scan tool to be able to pull the codes from the TCCM on your truck. A generic OBD2 scan tool will not be able to do it.

If the light is on or was on, there should be a stored code. That code will be the starting point for diagnosing your problem given that you have not stated any other driveability concerns.

 

thanks for the input
no prob. driing
goes in and out of 4 WD both High and low
I have a buddy with a scan tool

 

Just an idea,
check any wires coming from the front axle for chafing or a ground that is loose
if there are tie wraps holding them cut them and look underneath to see if the jacket has worn thru
Hope it helps

 

Fixed it I hope
Replaced all vacume lines
shift's in 4wdh 4wdl 4wd auto
and back to 2wdh
the light on the switch for 2-3 seconds and i can hear a click by the tccm
AND HEAR THE SHIFT UNDER THE TRUCK is this right
no SERVICE 4WD light for 2 days now
and the engine runs smoother
i guess it had a big leak that sucked

 

OK the damm Service 4Wd light came back on
Pulled A code B2725 Transfer case mode switch
is the 4 button switch on the dash or on the transfer case

 

I think thats the one on the transfer case.

 

I've been reading up on this all eveing and what I've found out that if the LED light's flash off and on then the transfercase locks uo and the diff locks also it's the switch on the dash
I am going to try that first