2018 Freightliner Cascadia - Active Code 1743 Engine Protection Override Switch Circuit High

Question

My Cascadia is throwing a constant amber dash light with code 1743 and won't clear even after a battery disconnect. The truck runs fine, but I'm worried it will derate or shut down if an actual engine protection event occurs. I noticed the switch on the dash feels a little loose but it doesn't seem to change state in DiagnosticLink.

Dave Kowalski · Accepted Answer

Found the issue. I traced the wire from the dash switch back to the CPC connector and found pin 14 was pushed back in the housing and touching a power lead. I depinned the connector, cleaned the terminal, and seated it properly with a new locking tab. Code cleared immediately and the override function now toggles correctly in the diagnostic software. Total cost was just my time and a $5 connector repair kit.

backyard_bart · Answer

On the DD15, SPN 1743 FMI 3 usually points to a short to power on the signal wire. If swapping the switch didn't work, trace the wiring from the switch back to the Cab Control Module or the CPC. It is likely a rubbed wire behind the center gauge cluster.

fleet_chief_42 · Answer

You need to check the parameters in DiagnosticLink. Sometimes the override switch logic gets messed up if someone tried to reflash the CPC or MCM without the correct template. Verify if the digital input is assigned to the correct pin in the software.

dieselmike88 · Answer

Have you checked the bulkhead connector for any signs of green crusties? Usually, a High Circuit code means the CPC is seeing a constant 5V or 12V reference where it expects a ground or a toggled signal. Check the pins on the back of the dash harness.

2018 Freightliner Cascadia - Active Code 1743 Engine Protection Override Switch Circuit High

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