2004 Avalanche 1500. We were getting the ABS and Brake warning lights. Transmission would sometines not shift properly. Often the speedo showed 25 MPH with car sitting still. Auto door locks would activate at rest. Got advice that vehicle speed sensors might be bad. I changed both VSS (why does it have two?) and cleaned all the weather pack connectors to the VSSs as well as front wheel speed sensors. The problem went away for a couple of weeks, now the problem comes back ocassionally. Most times all is OK. Any ideas as to what do look for next?
Joe B