6.7 Cummins DEF Delete and SCR Removal Guide

Written by Derek Miller

June 01, 2026

If you own a 2013-or-newer Ram 2500 or 3500 with the 6.7 Cummins, you already know the DEF system is one of the most frustrating maintenance headaches on the platform. DEF injector failures, frozen lines, bad NOx sensors, and power derates that leave you stranded on the side of the road, which crucially none of that exists on pre-2013 trucks.

This guide breaks down exactly what a 6.7 Cummins DEF delete involves, what parts you need, how installation works, and why most experienced diesel owners choose to go full delete instead of stopping at DEF alone.

1. What Is the DEF/SCR System on the 6.7 Cummins? 2. How the Cycle Works 3. Why Cummins Owners Delete the DEF System 4. What a 6.7 Cummins DEF Delete Includes 5. Step-by-Step DEF Delete Installation 6. DEF Delete Alone vs. Full Delete (DPF + EGR + DEF) 7. FAQ 8. Ready to Delete Your 6.7 Cummins DEF System?

What Is the DEF/SCR System on the 6.7 Cummins?

Cummins introduced Selective Catalytic Reduction (SCR) on the Ram 6.7L starting with the 2013 model year. Before 2013, your truck handled NOx emissions entirely through EGR. After 2013, Ram added a second layer: a urea-based aftertreatment system that injects Diesel Exhaust Fluid (DEF) into the hot exhaust stream ahead of the SCR catalyst.

How the Cycle Works

Exhaust gas exits the turbo, passes through the DPF, and then enters the SCR canister. A DEF injector sprays a fine mist of urea upstream. Heat causes the urea to convert to ammonia, which reacts with NOx over the SCR catalyst and breaks it down into nitrogen and water vapor.

The system relies on a DEF quality sensor, a DEF level sensor, a NOx sensor upstream of the SCR, and a second NOx sensor downstream to verify conversion efficiency. When any of these components fail, the ECM triggers fault codes. Depending on severity, it will initiate a power derate that limits engine output until the fault is cleared.

Why Cummins Owners Delete the DEF System

DEF Injector Failures

The doser injector on the 6.7 Cummins is a known weak point. The injector tip is exposed to extreme exhaust temperatures and carbon buildup. Over time, the tip crystallizes with urea deposits, causing clogging or complete failure. Replacement parts run $300–$600, and labor adds up fast if a shop needs to remove exhaust components to access it.

DEF Quality Sensor Issues

The DEF quality sensor monitors the concentration of urea in the tank. Contaminated fluid, old DEF, or even certain aftermarket DEF brands can trigger fault codes like P207F. This sets a CEL, and if the truck thinks the DEF quality is out of spec, it will begin a countdown to derate.

Power Derate When DEF Runs Low

This is the one that really gets people. If your DEF level drops below a certain threshold and you ignore the warning lamps long enough, the ECM will derate your engine, typically limiting your speed to 5 mph. On a work truck pulling a load, that's not a warning, it's a forced shutdown. Many fleet operators and owner-operators have had enough of that risk.

What a 6.7 Cummins DEF Delete Includes

A proper DEF delete on the 6.7 Cummins is a three-part solution: hardware, electronics, and a tune.

1. SCR Bypass Pipe

The SCR canister sits behind the DPF in the exhaust path. A stainless steel bypass pipe replaces both the DPF and SCR assembly, eliminating flow restriction and all the associated sensors. Most quality pipes are mandrel-bent T409 stainless, available in 4" or 5" diameter.

2. DEF Emulator Module (NOx Sensor Delete)

The ECM monitors two NOx sensors. Without an emulator, removing the SCR will immediately throw multiple fault codes and send the truck into limp mode. A DEF emulator module plugs into the factory NOx sensor harness and feeds the ECM simulated signals, telling it everything is functioning normally. This is non-negotiable for a clean, code-free delete.

3. ECU Tune for SCR-Off Operation

The tune is what ties everything together. The ECM needs to be reflashed to disable DEF dosing commands, turn off DPF regen logic, suppress NOx fault codes, and recalibrate fueling and boost targets for the now-unrestricted exhaust. A proper 6.7 Cummins tuner handles all of this and typically allows switching between multiple tunes without returning to a laptop.

Step-by-Step DEF Delete Installation

2013–2018 vs. 2019–2024 Differences

The core process is the same across generations, but the 2019–2024 trucks use a revised exhaust aftertreatment package with a combined DPF/SCR canister and updated NOx sensor locations. The emulator wiring differs slightly between the two generations, so make sure your kit is year-matched before ordering.

Step 1 — Flash the Tune First

Always tune before you touch hardware. Connect your delete tuner to the OBD-II port, select the appropriate delete tune for your year and configuration, and let it flash the ECM. This prevents the truck from throwing immediate derate flags once the sensors are disconnected.

Step 2 — Disconnect Sensors and Remove Exhaust

With the engine cool and batteries disconnected, unplug the upstream NOx sensor, downstream NOx sensor, DEF injector connector, DEF doser line, and DEF pressure sensor. Remove the factory DPF and SCR assembly. On most Ram trucks, this is a bolted flange at the downpipe and a hanger system underneath.

Step 3 — Install the Bypass Pipe

Drop in your stainless bypass pipe and torque the flanges to spec. Make sure all sensor bungs are capped if you're not using emulator sensors in those locations.

Step 4 — Wire the NOx Emulator

Plug the emulator module into the factory NOx sensor harness connections. Most quality emulators are plug-and-play, meaning no splicing is required. Tuck the module somewhere safe away from heat.

Step 5 — Clear DTCs and Verify

Reconnect the battery, start the truck, and confirm there are no active fault codes. Many tuners allow you to read and clear codes on the handheld screen. Do a short drive cycle and verify the truck holds idle and throttle response without any derate warnings.

DEF Delete Alone vs. Full Delete (DPF + EGR + DEF)

Here's the honest truth: most experienced diesel guys don't recommend a DEF-only delete. Here's why.

The DPF sits upstream of the SCR in the exhaust stream. If you remove the SCR but leave the DPF in place, you're still dealing with a clogged filter, forced regen cycles, and elevated EGTs under load. You've eliminated one headache but kept the bigger one.

The EGR system is its own separate problem. Soot buildup in the intake, EGR cooler failures, and throttle valve carbon deposits are all classic 6.7 Cummins complaints. A 6.7 Cummins EGR delete kit addresses those issues directly, and it's a natural companion to any exhaust delete.

A full delete — DPF + EGR + DEF — is where you get the full performance picture: lower EGTs under tow, 2–4 MPG improvement, 30–60 HP gain depending on tune aggressiveness, and zero emissions system maintenance costs going forward.

Cost Comparison

Delete Type	Approx. Parts Cost	What You Keep
DEF Only	$400–$700	DPF issues, EGR soot
DPF + DEF	$600–$1,000	EGR problems
Full Delete (DPF + EGR + DEF)	$900–$1,500	Nothing to fix

The 6.7 Cummins delete kit bundles the essential hardware together and is the most cost-efficient path if you're going full delete. For the all-in-one approach that includes pipe, EGR plates, DEF module, and tuner in a single order, the diesel all-in-one delete kit collection has year-specific configurations for 2013–2017 and 2019–2024 trucks.

FAQ

Will deleting the DEF system throw check engine lights?

Not if you use a proper NOx emulator and a delete tune together. The emulator handles sensor simulation and the tune suppresses fault code monitoring. Done correctly, the dash stays clean.

Can I delete just the DEF and keep the DPF?

Technically yes, but it's not recommended. The DPF causes more day-to-day problems than the SCR on most trucks. Most guys who start with a partial delete end up going full delete within a year anyway.

Does a DEF delete hurt reliability?

The opposite, in most cases. You're removing complex, failure-prone emissions hardware and replacing it with a straight pipe and a tune. There's less to break and your EGTs run cooler under load.

What tuner should I use?

For the 6.7 Cummins, the Mini Maxx V2 is the most popular plug-and-play option. If you want more flexibility for custom calibration, EZ Lynk Auto Agent 3 and HP Tuners are solid choices. Any of the options in the 6.7 Cummins tuner collection come pre-loaded with delete-ready tunes.

Does this void my warranty?

Any emissions-related modification voids federal emissions compliance and will void your powertrain warranty on a vehicle still under coverage. The vast majority of truck owners doing a delete are past factory warranty at this point.

Ready to Delete Your 6.7 Cummins DEF System?

If you want year-matched kits with everything included (bypass pipe, NOx emulator, EGR hardware, and delete tuner), browse the 6.7 Cummins delete kit collection or go straight to the diesel all-in-one delete kit for a complete, single-order build. EngineGo ships same day or next day with free shipping, and every kit is application-specific to guarantee an exact fit.

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