DD15 SPN 641 FMI 15 Turbo Actuator Over Temp - Derate issues

Question

My 2018 Freightliner Cascadia is throwing a SPN 641 FMI 15 code and going into a partial derate. The dash shows a check engine light and I can hear the turbo actuator cycling weirdly when I key on. It seems to happen mostly when I am pulling a heavy load through the mountains.

Luis Hernandez · Accepted Answer

The issue was a restricted coolant supply line to the turbo actuator. I disconnected the small feed line and found a piece of casting slag/debris blocking the orifice. I replaced the actuator (Part # EA0031503794), the coolant lines, and the mounting gasket. After performing a VNT Learnt Performance test in Diagnostic Link 8.15, the truck is back to full power and the temps are staying within spec. Cost of the actuator was about $850.

Brian O'Connor · Answer

FMI 15 usually indicates a high temperature condition but not necessarily a failed component yet. Check your coolant lines going to the actuator to make sure they aren't kinked or clogged, as these actuators are liquid cooled on the EPA10 and newer models.

Dave Kowalski · Answer

You need to run the VNT hysteresis test using Detroit Diagnostic Link. If the movement is chunky or it fails the calibration, the internal gears in the actuator are likely stripping or the heat has already cooked the circuit board.

Pete Sanders · Answer

Verify that your exhaust manifold isn't leaking right onto the actuator. I've seen warped manifolds spray hot gas directly onto the electronics housing, triggering the over-temp code even if the cooling system is working fine.

DD15 SPN 641 FMI 15 Turbo Actuator Over Temp - Derate issues

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