exhaust

SCR Catalyst

for 2014 Ram 2500 6.7L I6 Cummins Diesel · 4WD

Difficulty

Advanced

Time

4.8 h

Tools

Steps

This procedure covers the removal and replacement of the SCR (Selective Catalytic Reduction) catalyst assembly on a 2014 Ram 2500 with the 6.7L Cummins diesel engine.

Warnings

⚠️Allow exhaust system to cool completely (minimum 2 hours) before starting work to prevent severe burns.

⚠️Diesel exhaust fluid (DEF) system is under pressure. Do not disconnect DEF lines unless system is depressurized.

⚠The SCR catalyst assembly weighs approximately 45-55 lbs. Use proper lifting technique and have an assistant available.

⚠Exhaust flange bolts are prone to seizing. Apply penetrating oil 24 hours before beginning work if possible.

ℹ️After SCR replacement, the vehicle will require a regeneration cycle and fault code clearing with a proper scan tool.

Tools required

Floor jack and jack stands rated for 3+ tonsEssential

Torque wrench (10-70 Nm range)Essential

Metric socket set (10mm-19mm)Essential

Oxygen sensor socketEssential

Penetrating oilEssential

Anti-seize compoundEssential

Wire brush

Exhaust hanger removal tool or pry bar

Safety glasses and glovesEssential

Creeper and work light

Scan tool for DPF/SCR system monitoringEssential

Parts

SCR catalyst assembly × 1 — Use OEM Mopar specification
Exhaust flange gasket (upstream) × 1 — Use OEM specification
Exhaust flange gasket (downstream) × 1 — Use OEM specification
NOx sensor (if damaged) × 1 — Use OEM specification
Exhaust hanger insulators (if deteriorated) × 2 — Replace as needed

Preparation

Park vehicle on level surface and allow exhaust system to cool completely (minimum 2 hours).
Disconnect both battery terminals, negative first, to prevent electrical issues during sensor removal.
Raise vehicle using floor jack and secure on jack stands rated for vehicle weight at all four corners.
Spray all exhaust flange bolts, hanger bolts, and sensor threads with penetrating oil. Allow to soak for 15-30 minutes.
Connect scan tool and document any existing fault codes related to SCR system before beginning work.

Procedure

1
Remove heat shields
Locate and remove the heat shields covering the SCR catalyst assembly. These are typically secured with multiple bolts along the length of the assembly. Remove all heat shield bolts and carefully lower shields away from exhaust components.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)
2
Disconnect NOx sensors
Locate the upstream and downstream NOx sensors on the SCR catalyst assembly. Disconnect the electrical connectors by pressing the release tabs. Using an oxygen sensor socket, carefully unthread both NOx sensors from the SCR housing. Inspect sensors for damage or excessive carbon buildup.
⚠NOx sensors are fragile and expensive. Use only an oxygen sensor socket to prevent damage to the sensor body.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
3
Disconnect DEF injector and lines
Locate the DEF injector mounted on the SCR catalyst assembly. Disconnect the electrical connector from the injector. Carefully disconnect the DEF supply line using appropriate wrenches. Have a drain pan ready as residual DEF fluid may drain from lines. Cap or plug DEF lines to prevent contamination.
⚠DEF is corrosive to certain metals. Wipe up any spills immediately and avoid skin contact.
4
Support SCR catalyst assembly
Position a transmission jack or suitable support under the SCR catalyst assembly to support its weight during removal. The assembly weighs 45-55 lbs and must be supported before disconnecting mounting points.
⚠Ensure support is positioned to prevent the assembly from falling or shifting during removal.
5
Remove exhaust hanger connections
Locate the exhaust hangers supporting the SCR catalyst assembly (typically 2-3 hangers). Using a pry bar or exhaust hanger tool, carefully separate the rubber insulators from the hanger brackets. Remove hanger bolts if necessary to provide clearance for SCR removal.
Torque spec
Hanger Bolts27 Nm (20 lb-ft)
6
Disconnect upstream exhaust flange
Locate the upstream flange connection between the DPF (Diesel Particulate Filter) outlet and the SCR catalyst inlet. Remove the exhaust flange bolts using appropriate sockets. If bolts are severely corroded, apply additional penetrating oil and use a breaker bar. Carefully separate the flange connection and remove the old gasket.
⚠If bolts are excessively corroded and cannot be removed, they may need to be cut and replaced with new hardware.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
7
Disconnect downstream exhaust flange
Locate the downstream flange connection between the SCR catalyst outlet and the tailpipe assembly. Remove the flange bolts and carefully separate the connection. Remove the old gasket. The SCR assembly should now be free from all exhaust connections.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
8
Remove mounting brackets
Remove any remaining mounting brackets or clamps securing the SCR catalyst assembly to the vehicle frame or undercarriage. These are typically secured with mounting bolts. Keep track of all hardware and bracket positions for reinstallation.
Torque spec
Mounting Bolts37 Nm (27 lb-ft)
9
Lower and remove SCR catalyst assembly
Carefully lower the SCR catalyst assembly using the transmission jack or support. Guide the assembly away from the vehicle, being mindful of remaining sensors, lines, or obstructions. Inspect the removed assembly for physical damage, cracks, or internal deterioration.
⚠Use proper lifting technique when handling the assembly. Have an assistant help guide it out if necessary.
10
Prepare new SCR catalyst for installation
Unpack the new SCR catalyst assembly and verify all mounting points and sensor ports match the original. Clean all flange mating surfaces on the DPF outlet and tailpipe inlet using a wire brush to ensure proper gasket sealing. Apply anti-seize compound to all exhaust flange bolt threads.
ℹ️Do not apply anti-seize to gasket surfaces, only to bolt threads as specified.
11
Install new SCR catalyst assembly
Position the new SCR catalyst assembly on the transmission jack or support and raise it into position. Align the upstream flange with the DPF outlet and downstream flange with the tailpipe inlet. Install new exhaust gaskets at both flange connections. Start all flange bolts by hand before tightening.
Torque spec
Exhaust Flange Bolts45 Nm (33 lb-ft)
12
Reinstall mounting brackets and hangers
Reinstall all mounting brackets and clamps to secure the SCR assembly to the vehicle frame. Torque mounting bolts to specification. Reinstall exhaust hangers, ensuring rubber insulators are properly seated in brackets. Verify the entire exhaust system is properly supported and aligned.
Torque spec
Mounting Bolts37 Nm (27 lb-ft)
Hanger Bolts27 Nm (20 lb-ft)
13
Reinstall NOx sensors
Apply anti-seize compound to NOx sensor threads only (avoid getting compound on sensor element). Thread both upstream and downstream NOx sensors into the SCR catalyst housing by hand, then torque to specification using an oxygen sensor socket. Reconnect electrical connectors to both sensors.
Torque spec
O2 Sensor45 Nm (33 lb-ft)
14
Reconnect DEF injector and lines
Reconnect the DEF supply line to the injector, ensuring proper seating and alignment. Tighten connection securely but do not overtighten. Reconnect the electrical connector to the DEF injector. Verify all DEF connections are secure and properly sealed.
ℹ️DEF system will self-prime during initial startup. Monitor for leaks during first operation.
15
Reinstall heat shields and finalize
Reinstall all heat shields in their original positions and torque heat shield bolts to specification. Remove all tools and supports from under the vehicle. Reconnect both battery terminals, positive first. Lower vehicle from jack stands.
Torque spec
Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

Double-check all exhaust connections are tight and properly gasketed before starting engine.
Verify all electrical connectors to NOx sensors and DEF injector are fully seated and locked.
Inspect for any tools or materials left in the work area before lowering vehicle.

Verification

Start engine and allow to idle. Listen for exhaust leaks at all flange connections. Inspect all connections visually for leaks or smoke.
Using scan tool, verify NOx sensor readings are being received and are within expected parameters (typically 0-100 ppm at idle).
Clear all stored fault codes related to SCR system. Monitor for any new codes during initial test drive.
Perform a test drive of at least 15-20 minutes to allow SCR system to reach operating temperature. Monitor exhaust temperature and NOx sensor data with scan tool.
After test drive, re-inspect all exhaust connections for leaks. Check DEF injector and lines for any signs of leakage.
Verify DEF level is adequate and no DEF warning lights are present on instrument cluster.
Allow engine to complete a full regeneration cycle if prompted by ECM to ensure SCR system is functioning properly with aftertreatment system.