P1451 on 2014-2020 Ram 2500 6.7L Cummins: Diesel Particulate Filter System Performance Guide

What's Unique About the 2014-2020 Ram 2500

On these Ram trucks, P1451 is a well-documented issue, often appearing as part of a cluster of aftertreatment system codes. The manufacturer has issued multiple Technical Service Bulletins (TSBs) that include P1451, often recommending a software update to the Powertrain Control Module (PCM). This suggests the original diagnostic logic was sometimes too sensitive or that the regeneration strategy needed refinement for real-world driving conditions, especially short trips, excessive idling, or operation in very cold temperatures which prevent the exhaust from reaching optimal temperatures. TSB 18-102-22 REV. A for 2020 models, for example, bundles a PCM update for P1451 with fixes for turbo underboost (P0299) and NOx catalyst efficiency (P20EE), showing how interrelated these systems are. [⭐ MANUFACTURER TSB — highest authority]

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: This range covers the end of the third generation (2014-2018) and the start of the fourth generation (2019-2020) Ram 2500. Both generations use the 6.7L Cummins engine with a DPF system. While the core causes and fixes for P1451 are consistent, specific part numbers for sensors or TSBs for software updates may differ. For example, the DPF pressure sensor for 2014-2018 models is Mopar P/N 68085750AB, while 2019-2020 models use P/N 68312096AB.

Symptoms You May Notice

• Check Engine Light (MIL) illuminated
• Message on the driver information center (EVIC), such as "Exhaust Filter Full See Dealer" or "CATALYST FULL: SEE OWNERS MAN".
• Reduced engine power (limp mode)
• Vehicle may be unable to perform active or passive DPF regeneration.
• Increased frequency of regeneration cycles before the code sets, particularly in cold weather.
• Noticeable decrease in fuel economy due to frequent, incomplete regeneration attempts.

Most Likely Causes

1. Clogged, Cracked, or Melted DPF Differential Pressure Sensor Hoses 🔴 High Probability The rubber/silicone hoses are exposed to high exhaust temperatures and road debris, causing them to become brittle, crack, melt, or get clogged with soot. This is the most common and cheapest failure point.
   How to confirm: Visually inspect the hoses running to the DPF differential pressure sensor for cracks, melting, or damage. Remove them and ensure they are clear by blowing compressed air through them. Crucially, also check the metal ports on the DPF housing where the hoses connect, as they are a common point for hard soot blockage that requires cleaning with a small wire or drill bit turned by hand.
   Typical fix: Clean the hoses and ports if clogged, or replace the hoses if damaged. A common replacement is the downstream hose, Mopar Part #68363177AC. This is a very common and inexpensive repair.
   Est. part cost: $20-$80
2. Faulty DPF Differential Pressure Sensor 🟡 Medium Probability The sensor itself can fail electronically from heat and vibration over time, sending irrational data to the ECM.
   How to confirm: With the hoses confirmed to be clear and intact, use a scan tool to monitor the DPF pressure sensor data. With the key on and engine off (KOEO), it should read 0.0 PSI. If the reading is stuck high, low, or doesn't change logically with RPM, the sensor has likely failed.
   Typical fix: Replace the DPF differential pressure sensor. It is typically mounted on a bracket on the transmission or frame rail. 🎬 Watch: How to diagnose and replace the differential pressure sensor. Part numbers differ by year: 2013-2018 models use Mopar #68085750AB (supersedes 68085750AA), and 2019-2024 models use Mopar #68312096AB (supersedes 68312096AA).
   Est. part cost: $70-$350
3. DPF Soot Overload (Needs Forced Regeneration) 🟡 Medium Probability Frequent short trips, excessive idling, or light-load driving prevent the exhaust from getting hot enough for a complete passive or active regeneration cycle, causing soot to build up. This is especially true in very cold climates.
   How to confirm: Check the DPF soot load percentage using a capable scan tool. If it is high but not at maximum, a forced regeneration may be possible.
   Typical fix: Perform a stationary (forced) DPF regeneration using a compatible scan tool (like AlfaOBD). Modifying driving habits to include more sustained highway time can also help prevent recurrence.
   Est. part cost: $0
4. Outdated Powertrain Control Module (PCM) Software ⚪ Low Probability Multiple TSBs have been issued by the manufacturer to update PCM software, which refines the diagnostic logic for the DPF system and can prevent false or premature P1451 codes. For example, TSB 18-102-22 REV. A for 2020 models requires that the Y78 fuel pump recall has been performed before the PCM update can be applied.
   How to confirm: A Ram dealership or a shop with a subscription to OEM data can check your vehicle's VIN to see if any software updates are available or have been performed. Key TSBs to reference are 18-102-22 REV. A (2020 models), 18-066-23 (2019 models), and 18-130-22 REVA (2016 models). [⭐ MANUFACTURER TSB — highest authority, ⭐ MANUFACTURER TSB — highest authority, ⭐ MANUFACTURER TSB — highest authority]
   Typical fix: Reprogram (flash) the PCM with the latest software. This is typically a dealer-level service.
   Est. part cost: $0-$200

Rare But Worth Checking

• DPF Ash Accumulation: Ash is the non-combustible material left after soot is burned off. Over many miles (typically 150,000+), it builds up and cannot be removed by regeneration. This is an end-of-life condition for the DPF. The companion code P242F often indicates this. [⭐ MANUFACTURER TSB — highest authority, 1]
• Underlying Engine Issue: P1451 can be a symptom of another problem causing excessive soot, such as faulty injectors, a stuck EGR valve, a failing turbocharger, or boost leaks. The provided TSBs often group P1451 with codes for these other systems. [⭐ MANUFACTURER TSB — highest authority]
• Faulty Thermostat: A thermostat stuck open (often setting code P0128) can prevent the engine from reaching the necessary temperature for DPF regeneration, especially in cold weather, leading to soot buildup and P1451. [1, ⭐ MANUFACTURER TSB — highest authority]
• Damaged DPF Sensor Wiring: The wiring harness for the DPF pressure sensor can become chafed or corroded, especially where it runs along the transmission bell housing, leading to an open or short in the circuit.

Diagnosis Steps

1. Read all stored DTCs. Note any other codes that are present, as P1451 is often a symptom of another issue.
2. Visually inspect the DPF differential pressure sensor hoses for cracks, melting, kinks, or signs of soot leakage.
3. Remove the hoses and the metal tubes they connect to on the DPF. Ensure they are completely clear of soot buildup using compressed air and a small wire or 1/8" drill bit (turned by hand) if necessary. This is a critical and often overlooked step.
4. Inspect the electrical connector and wiring for the DPF pressure sensor for corrosion, damage, or loose pins, paying attention to the harness routing near the transmission.
5. Using a scan tool, monitor the DPF pressure sensor voltage/pressure with the key on/engine off (should be 0 or very close) and at idle. The reading should be low (e.g., 0.1-0.3 psi) and increase smoothly with RPM.
6. If sensor readings are illogical or stuck after confirming hoses and ports are clear, replace the DPF differential pressure sensor.
7. If sensors and hoses are good, check the DPF soot load with the scan tool. If high, attempt a stationary DPF regeneration using the scan tool.
8. If regeneration fails or the code returns quickly, investigate underlying causes for excess soot (EGR, turbo, injectors) or consider that the DPF is at the end of its life due to ash accumulation (check for P242F).

Parts You'll Likely Need

• DPF Differential Pressure Sensor Hoses — These hoses are the most common failure point, becoming clogged with soot or cracking from heat, leading to incorrect pressure readings.
  Trusted brands: Mopar, Dorman
  OEM price range: $50-$80
  Aftermarket price range: $20-$40
• DPF Differential Pressure Sensor — If the hoses are clear, the sensor itself is the next most likely component to fail, providing incorrect data to the ECM.
  Trusted brands: Mopar, Bosch, Standard Motor Products
  OEM price range: $150-$350
  Aftermarket price range: $70-$150
• Diesel Particulate Filter (DPF) — This is the last resort. It's needed only when the filter is confirmed to be internally damaged or so full of hardened ash that it cannot be cleaned by regeneration or professional cleaning services.
  Trusted brands: Mopar, Walker Exhaust, Dorman
  OEM price range: $2000-$3000
  Aftermarket price range: $1000-$2000

Related Codes That Often Appear With This One

• P2463 — Indicates 'Diesel Particulate Filter Restriction - Soot Accumulation,' which is a more direct measurement of the DPF being clogged with soot, the direct cause of P1451. [⭐ MANUFACTURER TSB — highest authority, 1]
• P242F — Indicates 'Diesel Particulate Filter Restriction - Ash Accumulation,' a long-term clogging issue that prevents proper performance and regeneration. [⭐ MANUFACTURER TSB — highest authority, 1]
• P20EE — Indicates 'NOx Catalyst Efficiency Below Threshold.' Problems in the DPF system can affect the entire aftertreatment chain, including the SCR/NOx system downstream. [⭐ MANUFACTURER TSB — highest authority, 1]
• P0299 — Indicates 'Turbocharger Underboost.' A poorly performing turbo can lead to incomplete combustion and excessive soot, which in turn clogs the DPF and triggers P1451. [⭐ MANUFACTURER TSB — highest authority, 1]
• P0128 — Indicates 'Thermostat Rationality.' A faulty thermostat can prevent the engine from reaching the required temperature for DPF regeneration, leading to P1451, especially in cold climates. [1, ⭐ MANUFACTURER TSB — highest authority]

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #1810222REVA: Groups P1451 with DPF soot/ash and turbo underboost codes, addressed by a PCM update. [⭐ MANUFACTURER TSB — highest authority]
• Bulletin #1806623: Groups P1451 with DPF soot/ash and NOx catalyst codes. [⭐ MANUFACTURER TSB — highest authority]
• Bulletin #1813022REVA: Lists P1451 among a wide variety of codes that can be addressed by a PCM software update. [⭐ MANUFACTURER TSB — highest authority]

Platform-Specific Known Issues

• Metal Port Clogging: A widely reported issue on owner forums is that the metal tubes on the DPF housing, where the pressure sensor hoses connect, get clogged with hard-packed soot. Many owners report that simply replacing hoses or the sensor does not fix the issue until these ports are manually cleaned out with a wire or small drill bit.
• Cold Climate Performance: Owners in colder regions report a significantly higher frequency of P1451 codes and regeneration cycles during winter months. This is often tied to a faulty thermostat (P0128), which prevents the engine from reaching the temperature required for the DPF to regenerate effectively.

Mechanic-Grade Diagnostic Values

• DPF Differential Pressure Sensor Signal Voltage (Key On, Engine Off) — expected: 0.5V - 1.0V. Failure: A reading outside this range, especially near 0V or 5V, suggests a faulty sensor or wiring issue.
• DPF Differential Pressure Sensor 5V Supply (KOEO) — expected: 4.9V - 5.1V. Failure: Voltage outside this range points to a problem with the PCM or the wiring from the PCM.
• DPF Differential Pressure Sensor Ground Circuit Resistance — expected: < 10.0 Ohms. Failure: Resistance higher than 10 ohms indicates a poor ground connection, which can cause erratic sensor readings.
• DPF Backpressure at Idle (Healthy DPF) — expected: 0.015 - 0.044 psi (1 - 3 millibars). Failure: Significantly higher pressure at idle suggests the DPF is clogged with soot or ash.

Scan Tool Commands That Help

• AlfaOBD: Stationary Desoot / Forced DPF Regeneration — Used to command the truck to perform a stationary regeneration cycle to burn off excess soot when the soot load is high but the DPF is not yet completely blocked. This is found under the Cummins engine controller options.
• AlfaOBD / Dealer Scan Tool: Reset DPF values / Replace DPF — After replacing the DPF assembly, this function must be used to tell the ECM that a new filter has been installed. This resets the learned soot and ash load values to zero, preventing the new filter from being treated as if it were old and clogged.

Wiring & Ground Locations

• DPF Pressure Sensor Harness Chafe Point — On the passenger side of the transmission bell housing, where the factory metal grounding strap is located.. The grounding strap can rub through the insulation of the DPF sensor's signal wire (often brown with a white stripe), causing the signal to short to ground. This can set codes like P2454 (DPF Pressure Sensor Circuit Low) and may contribute to P1451 performance issues by providing an incorrect signal to the ECM.
• DPF Pressure Sensor Connector — The sensor is typically mounted on a bracket on the transmission or frame rail, with a 3-pin or 4-pin connector.. This connector is the primary test point for checking the 5V reference, ground, and signal wires with a multimeter to diagnose a faulty sensor or wiring issue.

Real Owner Repair Stories

• Ram Heavy Duty Forum user 'Truck' (2021 Ram 2500) — Persistent P1451, P242F, and P2463 codes, even after multiple regeneration cycles.
  ❌ Tried (didn't work) Replacing the entire DPF and SCR assembly with a known-good used unit., Using a scan tool to reset the DPF values and performing multiple forced regens.
  ✅ What actually fixed it The issue was not resolved in the thread, but other users pointed out that the problem was likely upstream of the DPF. Suggested causes included a wrong air filter, a clogged CCV filter, boost leaks, or a bad EGR valve, all of which can create excessive soot and overwhelm the DPF system regardless of its condition.
• Ovens Garage YouTube Channel (2009 Ram 3500 6.7L Cummins (3rd Gen, but wiring chafe point is relevant)) — Check Engine Light with code P2454 (DPF Pressure Sensor A Circuit Low), a closely related code.
  ❌ Tried (didn't work) Replacing the DPF pressure sensor with a new part.
  ✅ What actually fixed it The factory metal grounding strap on the passenger side of the transmission bell housing had rubbed through the insulation of the DPF sensor's signal wire (brown with a white stripe), causing it to short to ground. Repairing the damaged wire and securing the harness away from the strap resolved the code.

OEM Part Supersession History

• 68085750AA → 68085750AB — Standard part revision and improvement.
• 68312096AA → 68312096AB — Standard part revision, possibly for improved measurement accuracy.

Model Year Variations Within This Range

• 2019-2020: The 2019 model year marked the start of the 4.5/5th generation Ram HD, which included a redesigned aftertreatment system. While the principles are the same, the DPF and SCR catalysts are larger, and the DPF pressure sensor part number changed from the previous generation.