I have a 99 1500 4x4 suburban gas 350 push button tcase. Guy I got it from removed the transmission. I had a transmission installed because original was gone. Problem I'm having is it will not shift. It takes off in first gear fine. No noises. I have reverse. No speedo. I have replaced the vss already which did not fix the speedo. It has new shift sylinoids. Also has new tps. Trans shop was able to make it shift with scanner hooked up but it would not do it on its own. Good fuses. Already replaced ignition. Brake lights work fine. I can put the shifter in low1 and shift to 2 and I get second but I can't get any other gears at all. Someone please help. ECM is new as well. I have abs light on which says loss of rear wheel speed sensor. C0236. When I hook my modis up to it put it in low and manually shift at column to second I can see 1-2 silinoid turn off and when I shift to drive 2-3 stays on. I can't get 3-2 to change either. Any help would be awesome. Dan

 

And I have a weird clicking noise by the pedals sometimes

 

Anybody have any ideas? Could the ebcm have anything to do with it?

 

Without the vss you will not get the trans to shift. Is the transfer case the same one that was originally in the vehicle? I'm assuming this is where the signal is coming from. If its not the original I would question if the signal component is the same as far as pulses per revolution or if its even there.

 

Yes the transfer case is the original one. I replaced the vss but did not check signal. How would I do that. I have 3 sensors that all appear to be the same I switched everyone with the new one and tested with no change. I'm assuming it would be the one closest to the rear driveline.

 

Yes generally the output is where we would read this with the sensor. Not sure why you would have three sensors that all look alike. Ill have to ask our transfer case guy that question next week. Here is a link for testing a vss. How To Test A 2 Wire Speed Sender - YouTube

 

Thanks Vince. Checked the link out but I don't have that style speed sensor. Mine I can't put a drill on. It's like a magnet.

 

If you have a Modis you should be able to test. You should have Component test on that tool. How old is the software???

 

You can do an AC Voltage test by back probeing the back of the connector and see if you get a voltage increase as speed increases. There is only 2 pins

VSS+ will be Yellow or Purple-White
VSS- will be Purple or Light Green-Black

Connect your Yellow test lead to VSS+
Connect your Black test lead to VSS-

You can check resistance on the sensor itself when disconnected.

On a 2WD 4L60E you should see 1377 Ohms to 3555 Ohms
On a 4WD 4L60E you should see 976 Ohms to 2354 Ohms

On a 4L80E you should see 1042 Ohms to 2088 Ohms but it doesn't say 2WD or 4WD

If the sensor is good I would say you have a wiring issue. But what you have already told us, I would suspect the wiring is broken somewhere in the harness. You will need to disconnect it from the ECU and the sensor and check for continuity.

Can you see the actual Vehicle Speed on the Scan tool when you drive the vehicle???
If not check the wiring.

The VSS signal at the ECU is on the Black C4 connector. Pin 3 and 4.
Pin 3 should be Dark Green-White
Pin 4 should be Dark Green

 

After countless hours of beating my head on this one I finally got it. Turns out the vss harness was damaged. Ran a new wire and trans works great. Thanks for all the help guys