2018 Freightliner Cascadia - Intermittent U0075 and Dash Gage Cluster Cycling

Question

Running down the interstate and my dash gages started dropping to zero and cycling back up repeatedly. The truck hasn't derated yet, but I'm seeing U0075 on the diagnostic screen and the ABS light is flickering. It seems to happen more frequently when hitting bumps or driving in heavy rain.

wrenchqueen · Accepted Answer

Found the issue after tracing the harness from the MCM. There was a rub-through in the harness loom right where it crosses over the starter motor. The yellow and green twisted pair for CAN C had worn through the insulation and was intermittently grounding out against a bracket. Repaired the wires using heat-shrink solder sleeves and rerouted the harness with more clearance. Total cost was about $15 in materials and 4 hours of diagnostic time.

Jordan Lee · Answer

U0075 typically points to a physical layer issue on the high-speed CAN link. Start by checking the terminating resistors; you should see 60 ohms across CAN Hi and CAN Lo with the batteries disconnected. If you see 120 ohms, one of your resistors or the circuit to it is open.

Sarah Thompson · Answer

Check the wiring harness behind the transmission or near the frame rails by the steer axle. The Cascadia is known for the harness rubbing against the p-clips, which can short the communication wires to the frame and pull the whole bus down.

obd2_owl · Answer

Check your Star Point connectors under the dash on the passenger side. If moisture gets into those green or grey blocks, it can cause the U0075 code and make the dash act crazy. Unplug the jumpers one by one to see if the symptoms go away.

2018 Freightliner Cascadia - Intermittent U0075 and Dash Gage Cluster Cycling

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