DPF Bypass Detected

PACCAR MX code P1615 (DPF Bypass Detected) is a serious-severity diagnostic trouble code set by the engine or aftertreatment control module on MX-11 and MX-13 engines in Kenworth and Peterbilt trucks. It indicates a fault in the aftertreatment system that should be diagnosed with DAVIE4 or PACCAR ESA.

Possibly — short distances may be OK, but ignoring the fault risks progressive damage, regen failure, or derate. Address promptly.

Typical repair runs $800-$6,000. Sensor or wiring repairs are at the low end; injector, DEF pump, DPF, or EGR cooler jobs are at the high end. Dealer-level DAVIE4 software is often required for programming or calibration after parts replacement.

California's heavy-duty OBD regulation requires the system to flag the PM filter before its filtering capability drops — from cracking, for instance — enough to push PM emissions past 0.07 g/bhp-hr, or past the applicable standard plus 0.06 g/bhp-hr, whichever is higher (Title 13 CCR 1971.1, section (e)(8.2.1)). Where no credible failure could reach that level, it must instead flag the case where no detectable filtering is happening at all. This threshold comes from the heavy-duty OBD regulation, which covers 2010 and later heavy-duty engines. If your engine is in a pickup at or under 14,000 lb GVWR it is certified under the separate medium-duty rule instead, so treat this as the design intent rather than your engine's exact limit.