Output Speed Sensor Check

Output speed sensor check. 1991 Two wheel drive C/K models:

Circuit Description:
The output sensor is the magnetic induction type. Gear teeth pressed on the outside diameter of the output carrier assembly induce an alternating current in the sensor. On two wheel drive vehicles, this current is transmitted to a digital ratio adapter where it is passed on to the PCM/TCM. Since vehicle speed is taken from the transfer case on four wheel drive vehicles, the transmission output sensor signal on these units goes directly to the PCM/TCM.

If the input sensor is not operational at start up, this can cause the output sensor to read zero.

Output speed sensor check. 1991 Two wheel drive C/K models:

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Test one checks the speed signal at the PCM/TCM.

2. Test two checks the output speed sensor directly.


Diagnostic Aids:
Check all connections, especially at the transmission pass-thru connector.