F-21, F-25: Left Front Pressure Sensor F-22, F-26: Right Front Pressure Sensor F-23, F-27: Left Rear Pressure Sensor F-24, F-28: Right Rear Pressure Sensor A common problem with sensors is connector failure. Often the connectors to the suspension pressure sensor are not secured to the truck and become caked with mud and debris. They become targets for the power washers used to clean the trucks at maintenance. Many problems with the pressure sensors can be relieved by disconnecting the connector, cleaning the terminals, reconnecting the connector halves, and securing the connector. Over time, the terminal crimps may fail and need to be replaced.
Check power supply voltage to the sensor between circuits 39F (red, 18vdc) and circuit 39FG (black, ground). Check the sensor output between circuits 39FA, 39FB, 39FC or 39FD (white, 1-5vdc) and circuit 39FG (black, ground). It may be helpful to check these voltages on the sensor side of the connector and on the harness side of the connector. Corrosion in the connector can affect voltages through the connection. Compare output voltage from the pressure sensor to the pressure inside the suspension. Use a pressure gauge to measure the pressure in the suspension. The output voltage from the pressure sensor is a 1-5vdc signal. This 4- volt span linearly represents 0 to 2845 psi.
For example, if the pressure in the suspension is 410 psi, the output voltage should be: vdc V output 576 .1 2845 410 4 1 = Ч + = Don’t forget to add the 1v since the output of the pressure sensor at 0 psi is 1 volt The generic version is: Ч + = 2845 _ 4 1 pressure Suspension V output M20007.2 3/02 Payload Meter II™ Troubleshooting M20-45