Ram ProMaster 3500 EcoDiesel NOx Sensor Replacement in Kirkland, WA: Damaged DPF Threads and a Soot-Loaded Filter

This 2014 Ram ProMaster 3500 came into our Kirkland shop at 195,418 miles with stored faults in its NOx sensor system. The van runs the 3.0L EcoDiesel. By the end of the job, the diesel particulate filter (DPF) had been out of the van and cleaned.

The diagnosis

We connected our diagnostic equipment and ran a full fault survey. The stored faults were in the NOx sensor system, and following the diagnostic test plan confirmed that the pre-catalyst NOx sensor had failed.

Given the age and condition of the system, we recommended replacing both NOx sensors as a set. See how we work through fault codes on our engine diagnostics page.

Damaged threads in the DPF

We removed the lower NOx sensor and its controller and installed a new sensor and controller assembly.

The upper sensor threads into the DPF, and it would start to loosen, then bind. We worked it out carefully with inductive heat and penetrating oil, but the sensor threads in the DPF were damaged by the time it came free.

Getting the DPF out

Repairing those threads properly meant removing the DPF, which also let us inspect the filter itself. On this van, that takes a lot of disassembly:

• Drained the cooling system, disconnected the EGR cooler hoses and removed the EGR cooler.

• Disconnected the DPF from the turbocharger and the lower exhaust.

• Removed the front grille, bumper and engine cooling fans.

• Disconnected the lower engine mount and moved the engine forward for the clearance to lift the DPF out.

With the DPF out, we found significant soot buildup and restriction inside the filter. We sent it to a partner shop for a complete off-vehicle cleaning and flush.

Putting it back together

We repaired the damaged NOx sensor threads in the DPF, reinstalled the cleaned filter and installed the new upper NOx sensor and controller. After verifying the sensor fit, we reassembled everything with new gaskets and clamps: EGR tube and EGR cooler gaskets, the turbo-to-DPF gasket and the downpipe band clamp.

Then we refilled and bled the cooling system, cleared all stored faults and performed the required EGR and SCR (the diesel exhaust fluid system) resets and adaptations. On the road test the system worked normally, and no related faults came back. More on our exhaust system repair work.

The work performed

• Diagnosis: full fault survey and NOx sensor test plan.

• Upstream and downstream NOx sensors with controllers, both genuine Mopar.

• EGR cooler, DPF, grille, bumper and cooling fans removed and reinstalled, with the engine moved forward for clearance.

• DPF threads repaired; DPF cleaned and flushed off the vehicle by a partner shop.

• New EGR, exhaust and DPF gaskets and the downpipe clamp.

• Cooling system refilled and bled; EGR and SCR resets and adaptations; road test.

What it cost

The job landed in the $5,300–$7,500 range, completed November 2026. The two genuine Mopar NOx sensors were the biggest parts cost. The rest came from just over 12 hours of labor to get the DPF out and back in, plus the off-vehicle DPF cleaning.

That range reflects a completed historical project, not a current quote.

Questions about this job

Why replace both NOx sensors when only one failed?

Testing confirmed the pre-catalyst sensor had failed. Given the age and condition of the system, we recommended replacing both as a set.

Why did the DPF have to come out?

The upper NOx sensor threads into the DPF, and those threads were damaged when the seized sensor came out. Repairing them properly meant removing the filter, which also let us inspect it.

Was the DPF replaced?

No. It had significant soot buildup, so it was cleaned and flushed off the vehicle by a partner shop, then reinstalled with the repaired threads.

Did the faults come back?

After the EGR and SCR resets and a road test, the system operated normally with no related faults returning at the time the van left.

Do you work on Ram diesels?

Yes. More on our Ram repair in Kirkland.

Prepared from our job records for this vehicle: the repair order and technician notes, the parts list, the partner shop’s DPF cleaning line and the final invoice.