Kenworth T680 SPN 520202 FMI 14 Load Disconnect Switch Error

Question

My 2019 T680 is throwing a SPN 520202 FMI 14 code on the dash and won't clear. The truck starts fine, but I'm getting a constant warning about a load disconnect switch state mismatch. I am worried it's going to trigger a derate or prevent the sleeper accessories from working correctly.

backyard_bart · Accepted Answer

The issue was a failed Load Disconnect Switch assembly (Part # K301-390-1). The internal microswitch that sends the 'State' signal to the CECU was failing intermittently. I replaced the floor-mounted switch and cleaned the 3-pin connector which had some green crusties. Topped off the repair by clearing the inactive faults with DAVIE4; total part cost was about $115 and it took 45 minutes to install.

Rachel Nguyen · Answer

This code usually means the Chassis Node is seeing a conflict between the physical switch position and the voltage it senses on the feedback circuit. Check the wiring harness near the battery box for any rubbing.

dieselmike88 · Answer

It is likely a bad Load Disconnect Solenoid. They are known to stick or have internal contact failure on these Paccar builds. You can bypass it temporarily to see if the code goes inactive.

Tom Patel · Answer

Have you checked the fuses in the Power Distribution Center? Sometimes a blown fuse on the logic side of the disconnect circuit will cause the controller to think the switch is open when it is actually closed.

Kenworth T680 SPN 520202 FMI 14 Load Disconnect Switch Error

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