DPF, DEF & Exhaust Repair in Tacoma, WA

DPF, DEF and SCR: what a derate actually costs you

An aftertreatment fault is not a check-engine light you can finish the week with. The engine derates — first to a soft limit, then to five miles an hour — and a loaded truck that derates on I-5 becomes a tow, a missed appointment and, for a drayage tractor, per-diem on a box that is still sitting on the chassis. The whole point of diagnosing it fast is that the cost of waiting is not the repair bill.

What we check, in order

1. Pull the codes and the freeze-frame data — not just the active code, but what the engine saw when it set it. A P20EE with a low DEF-quality history is a different repair from the same code with a failed NOx sensor.
2. Soot load and differential pressure across the filter, measured rather than assumed. A filter reading high on delta-P with low soot is telling you about ash, not about your driving.
3. Regen history — how many parked regens, how many aborted, how far apart. A truck that regenerates every 200 miles has an upstream problem, and cleaning the filter will not fix it.
4. The upstream cause: EGR cooler, injectors, turbo, boost leaks, a dosing valve that is not dosing. Cleaning a DPF without finding what loaded it is a repair you pay for twice.
5. DEF quality and the dosing system — concentration, contamination, pump pressure, lines and heaters, and whether the tank has been topped with something that is not DEF.
6. NOx and temperature sensors, wiring and connectors — the cheapest failure in the system and the one most often replaced when the harness was the problem.

Forced regen, cleaning or replacement

Three different answers, and which one is right depends on the measurements above, not on the mileage.

• Forced (parked) regen — the filter is loaded with soot but the substrate is sound. Fast, and pointless if the reason it loaded is still there.
• Cleaning — ash has accumulated past what regeneration can burn off. The filter comes out, gets cleaned and flow-tested, and goes back in. This is normal maintenance on a high-mileage engine, not a failure.
• Replacement — the substrate is cracked, melted or plugged beyond cleaning. Expensive, and worth confirming with a flow test rather than a guess.

Engines we see most

Detroit DD13 / DD15 / DD16, Cummins ISX and X15, Paccar MX-13, Volvo D13 and Mack MP8 — the engines that actually run the South Sound. Each family fails in its own way and we write about what we see: Detroit DD15 common problems, Volvo D13 and Mack MP8, Paccar MX, EGR cooler failure and what a derate is telling you.

If you are derating right now

Call (425) 900-6212 before you decide whether to keep driving. We can pull codes at the roadside across the South Sound and tell you whether the truck makes it to the shop in Tacoma or whether it stops where it is. That call is free and it is usually the difference between a repair and a tow.