Hello have a 94 GMC C1500 5.7 4L60E the trans won`t shift and the MPH don`t work.
Hooked up scanner to see the VSS MPH it show 0-speed .Check for AC volt at the speed sensor .the volt go up with higher engine RPM ,check for AC volts at the speed buffer coming from the speed sensor have AC volts there so the wiring good .also check for DC volt coming out of the speed buffer my chart tree says 1.0 to 2.5 DC volt I have 5.04 DC volts.also hooked a ground to the black and white wire on the speed buffer and the black and white wire on the ECM to make sure they had ground have unplugged the cruise control under the hood .I have changed the buffer and the ECM (? does the speed buffer number have to match the one in the truck .this I was unable to fine at a salvage yard new one $160.00 from dealer also clean the G109 and G108 ground .so any GM guys out there that can help thanks