Volvo VNL 780 Intermittent Communication Failure U3472

Question

My 2018 Volvo VNL 780 with the D13 engine is throwing a U3472 code and going into a partial derate mode while on the highway. I'm losing my instrument cluster gauges momentarily and getting a 'Check Transmission' warning at the same time. It seems to happen more frequently when hitting bumps or driving in heavy rain.

Carlos Diaz · Accepted Answer

Found the issue after a deep dive into the harness. The main engine-to-chassis harness (part number 21455589) had a rub-through point against the steered steering column shaft bracket. The green/yellow twisted pair for the J1939 was exposed and shorting to the chassis. I repaired the wires with heat-shrink solder sleeves and repositioned the loom with heavy-duty zip ties. Total cost was about $15 in materials and a few hours of tracing. The U3472 cleared immediately and hasn't returned in 5,000 miles.

Mike Reynolds · Answer

Check the wiring harness where it passes over the bell housing. Those looms are notorious for rubbing through and grounding out the CAN high or low lines, which will cause the intermittent dash dropouts you are seeing.

turbo_tony · Answer

U3472 on these Volvos usually points to a data link issue specifically between the TECU and the rest of the J1939 backbone. Check the terminator resistors at the rear of the frame and behind the dash to ensure you are seeing 60 ohms across the bus.

Megan Rivera · Answer

Have you looked at the pass-through connector on the firewall? If moisture gets in there, it can bridge the pins and cause the U3472 manufacturer-specific network code. Blow it out with contact cleaner and use some dielectric grease.

Volvo VNL 780 Intermittent Communication Failure U3472

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