Three regen types
Passive: natural during highway driving. Active: ECM-initiated mid-route via post-injection fuel. Parked: driver-initiated when active fails — truck must be stationary with a clear 25 ft radius.
Drivers see 'regen in progress' and panic. Service writers see 'failed regen' and replace parts. Both miss what's actually happening.
A failed regen is almost never a DPF problem — it's a soot-load problem caused by something upstream.
Passive: natural during highway driving. Active: ECM-initiated mid-route via post-injection fuel. Parked: driver-initiated when active fails — truck must be stationary with a clear 25 ft radius.
Soot load 80%+, derate warning, or post-repair after replacing exhaust sensors. Don't interrupt unless safety-critical — interrupting damages the substrate.
Almost always upstream: stuck-open injector, EGR cooler failure, boost leak, DEF dosing issue. Replace the DPF without fixing upstream and you'll be back in 30K mi.
Yes — active and passive regens happen while driving and don't require any action. Parked regens require the truck to be stationary.