P1451 on 2014-2020 Ram 3500: Diesel Particulate Filter Performance Fixes

What's Unique About the 2014-2020 Ram 3500

On the 6.7L Cummins engine, the P1451 code is a very common flag related to the complex aftertreatment system and is often a symptom rather than the root cause. Ram has issued multiple Technical Service Bulletins (TSBs) that involve software updates to refine the logic for DPF monitoring, indicating the truck's computer can sometimes misinterpret sensor data or struggle with certain driving cycles, like frequent short trips. The problem is so common that the primary suspects are often simple, inexpensive components like the sensor's rubber hoses and their metal connection ports, rather than the costly DPF assembly itself. Owners on forums like 'cumminsforum.com' and 'hdrams.com' frequently report success after thoroughly cleaning these components.

Diagnostic Flowchart

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

Generation note: This year range covers the end of the Fourth Generation (2014-2018) and the start of the Fifth Generation (2019-2020) Ram 3500. Both generations use the 6.7L Cummins engine, but with updates to the emissions system and software. The provided NHTSA TSBs cover models in both generations, indicating P1451 is a relevant issue for both. Part numbers for the DPF pressure sensor differ between these generations; 2013-2018 models use Mopar #68085750AB, while 2019+ models use Mopar #68312096AB.

Symptoms You May Notice

• Message on the Electronic Vehicle Information Center (EVIC), such as "CATALYST FULL: SEE OWNERS MAN" or "Exhaust Filter Full See Dealer".
• Check Engine Light may or may not be illuminated, as the EVIC message is the primary warning.
• Reduced engine power or 'limp mode', especially if the warning is ignored.
• Active DPF regeneration may be disabled by the PCM.
• Vehicle may fail an emissions test.
• Frequent or failed attempts by the truck to enter a regeneration cycle.

Most Likely Causes

1. Clogged or Damaged DPF Pressure Sensor Hoses/Ports 🔴 High Probability The rubber hoses are exposed to extreme exhaust heat, causing them to become brittle, crack, or melt. The metal ports on the DPF where they connect are a bottleneck and are highly prone to getting plugged with hard-packed soot.
   How to confirm: Visually inspect the rubber hoses for cracks, melting, or brittleness. Remove the hoses and blow compressed air through them to check for blockages. Use a small wire or a 1/8" drill bit turned by hand to carefully clean the metal ports on the DPF housing, as this is a very common and often overlooked blockage point.
   Typical fix: Replace the damaged rubber hoses and thoroughly clean the ports. This is a low-cost repair that solves the issue in a majority of cases.
   Est. part cost: $15-$50
2. Faulty DPF Differential Pressure Sensor 🟡 Medium Probability The sensor itself can fail electronically from constant heat and vibration, causing it to send irrational or stuck voltage signals to the PCM.
   How to confirm: With a capable scan tool, monitor the DPF pressure sensor readings at idle and while raising RPM. If the readings are stuck, irrational, or do not change, the sensor is likely faulty. With the key on, engine off, the signal wire should read between 0.5V and 1.0V; a reading near zero suggests a fault. Also inspect the wiring and connector for damage or corrosion, paying close attention to a potential chafe point against a transmission ground strap.
   Typical fix: Replace the DPF differential pressure sensor. It is typically mounted on a bracket on the passenger side of the transmission or frame rail.
   Est. part cost: $70-$200
3. Outdated Powertrain Control Module (PCM) Software 🟡 Medium Probability Ram has released multiple software updates (e.g., TSBs 18-102-22 REV. A, 18-066-23) to improve the DPF monitoring logic and prevent false triggers of this code.
   How to confirm: A Ram dealership or a shop with a subscription service can check your vehicle's VIN against the TSB database to see if a software update is available. Note that some updates, like TSB 18-102-22, require other recalls (like Y78 fuel pump recall) to be performed first.
   Typical fix: Reprogram (flash) the PCM with the latest software. This must be done by a dealer or qualified shop.
   Est. part cost: $0-$200
4. Driving Habits / Insufficient 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. This is a common issue for trucks used primarily for commuting rather than towing or highway driving.
   How to confirm: Review driving habits. Use a scan tool to check the 'Soot Load Percentage' of the DPF. If it's high and the truck is rarely driven at highway speeds, this is a likely cause.
   Typical fix: Drive the vehicle at sustained highway speeds (over 50 mph) for 30-45 minutes to initiate an active regeneration. If that fails, a forced stationary regeneration may be required using a capable scan tool.
   Est. part cost: $0
5. Upstream Engine or System Failure ⚪ Low Probability Problems that cause the engine to produce excessive soot can overwhelm the DPF system. This includes issues with a stuck EGR valve, boost leaks from the intercooler or boots, a clogged CCV filter, or faulty fuel injectors.
   How to confirm: Scan for other trouble codes. The presence of codes for the EGR valve (P0401), turbocharger (P0299), or fuel system points to an upstream problem. A failing thermostat (P0128) can also prevent the engine from reaching the required temperature for regeneration.
   Typical fix: Diagnose and repair the root cause (e.g., clean/replace EGR valve, repair boost leak) before addressing the DPF system.
   Est. part cost: $200-$2000+

Rare But Worth Checking

• Diesel Particulate Filter (DPF) Clogged with Ash: While P1451 often relates to soot, if the truck has high mileage, the DPF can become clogged with ash, which is the non-burnable byproduct of regeneration. This is indicated by code P242F and requires professional cleaning or DPF replacement.
• Wiring Harness Chafe: There is a documented failure point on some Ram models where the DPF sensor wiring harness can rub against a metal ground strap on the passenger side of the transmission bell housing. This can short the signal wire to ground, causing erratic readings and triggering P1451 even if the sensor and hoses are good.

Diagnosis Steps

1. Check for any applicable TSBs for your vehicle's VIN, especially regarding PCM software updates. A dealer can verify this for you.
2. Scan for all DTCs. If other codes are present (especially for EGR, turbo, fuel system, or thermostat), diagnose and fix them first, as P1451 is often a symptom.
3. Visually inspect the DPF differential pressure sensor hoses for cracks, melting, or blockages. Remove them and ensure they are clear by blowing compressed air through them.
4. Crucially, inspect the metal ports on the DPF where the hoses connect. They are prone to clogging with hard soot; clean them thoroughly with a small wire or a 1/8" drill bit turned by hand.
5. Inspect the electrical connector and wiring for the DPF pressure sensor for corrosion, damage, or loose pins. Pay special attention to the harness routing near the transmission for any signs of chafing against other components.
6. Using a scan tool, monitor the DPF pressure sensor voltage with the key on, engine off (should be ~0.5-1.0V) and at idle. Compare the readings to the expected values to determine if the sensor is faulty.

Parts You'll Likely Need

• DPF Pressure Sensor Hoses (OEM #Upstream: 68363173AC, Downstream: 68363177AC) — These rubber/silicone hoses are the most common failure point, as they crack, melt, or get clogged with soot, leading to incorrect pressure readings.
  Trusted brands: Mopar, Gates, Dorman
  OEM price range: $40-$80
  Aftermarket price range: $15-$40
• DPF Differential Pressure Sensor (OEM #68085750AB (for 2013-2018) / 68312096AB (for 2019-2020)) — If the hoses and ports are clear, the sensor itself is the next most likely part to fail, providing incorrect data to the PCM. Part number varies by generation.
  Trusted brands: Mopar, Bosch, Standard Motor Products
  OEM price range: $70-$250
  Aftermarket price range: $50-$150

Related Codes That Often Appear With This One

• P2463 — This code for 'DPF Restriction - Soot Accumulation' is a more severe and specific indicator of the same problem. P1451 is often the initial warning.
• P242F — This code for 'DPF Restriction - Ash Accumulation' indicates the filter is clogged with a non-burnable material, which often requires professional cleaning or replacement and can be the underlying reason for the P1451 performance issue.
• P20EE — This code for 'NOx Catalyst Efficiency' is often listed in the same TSBs as P1451 (e.g., TSB 18-102-22 REV. A), indicating a broader issue within the aftertreatment system that may be addressed by a single software update. [Bulletin #1810222REVA, #1806623]
• P0299 — 'Turbocharger Underboost' can cause the engine to produce excessive soot, overwhelming the DPF and triggering P1451. [Bulletin #1810222REVA]

Technical Service Bulletins (TSBs) & Recalls

• 18-102-22 REV. A (NHTSA ID 10214635): For 2020 models, this TSB is a PCM software update for a list of DTCs including P1451. It requires that recall Y78 (fuel pump) has been performed first.
• 18-066-23: For 2019 models, this TSB includes a PCM software update for a list of codes including P1451, P242F, and P2463.
• 18-130-22 REV. A: For 2016 models, this TSB lists P1451 as one of several codes that can be resolved with a PCM software update.
• 18-101-22 REV. A (NHTSA ID 10214634): For 2019 models, this TSB is a PCM reflash to address P1451 among other codes.

Platform-Specific Known Issues

• Repair Order is Critical: Technicians and experienced owners strongly advise against replacing the expensive DPF assembly as a first step. The diagnostic path should always start with the cheapest and most common failure points: hoses, ports, wiring, and software.
• Overlooked Clogged Ports: Many DIY repairs fail because only the rubber hoses are checked. The metal tubes on the DPF housing itself are a major chokepoint for hard-packed soot and must be cleared out, often with a small drill bit or stiff wire, for the system to read pressure correctly.
• Wiring Harness Chafe Point: On the passenger side of the transmission, the DPF sensor wiring harness can rub against a metal grounding strap. This can wear through the insulation on the signal wire, causing a short to ground and triggering sensor performance codes like P1451 even if the sensor and hoses are perfectly fine.

Mechanic-Grade Diagnostic Values

• DPF Differential Pressure Sensor Signal Voltage — expected: 0.5V to 1.0V with Key On, Engine Off (KOEO).. Failure: A reading near 0V or significantly outside the expected range suggests a faulty sensor or wiring issue.
• DPF Differential Pressure Sensor 5V Supply — expected: ~5.0V at the sensor connector with Key On.. Failure: Lack of 5V indicates a problem with the wiring or the PCM.
• DPF Differential Pressure Sensor Ground Circuit — expected: Less than 50 mV when back-probed at the connector.. Failure: Higher voltage indicates a poor ground connection.

Scan Tool Commands That Help

• wiTECH, AlfaOBD, Launch, Snap-on or other capable scan tool: DPF Replacement / PM Filter Replacement — This function MUST be performed after replacing the DPF assembly. It resets the PCM's soot and ash counters to zero, informing the system that a new, clean filter is installed. Failure to do this will cause continued faults.
• wiTECH, AlfaOBD, or other capable scan tool: Forced Stationary Regeneration / Stationary Desoot — Used to manually command a DPF regeneration cycle when the truck is parked. This is necessary when driving conditions have not allowed an automatic regen to complete and the soot level is critically high.
• wiTECH or other capable scan tool: Cylinder Cutout Test — If an upstream engine issue is suspected of creating excess soot, this test can help diagnose a leaking or malfunctioning fuel injector by disabling cylinders one by one and monitoring engine performance.

Wiring & Ground Locations

• DPF Pressure Sensor Connector — The sensor is typically mounted to a bracket on the passenger side of the transmission or frame rail. The connector is a 3-pin plug.. This is the primary point for electrical testing. Pin functions are typically: 5V Supply (Violet/White wire, circuit K354), Signal (Brown/White wire, circuit K355), and Ground/Return (Brown/Violet wire, circuit K951).
• Harness Chafe Point — On the driver's side of the transmission bell housing, where the DPF sensor wiring harness can rub against the factory ground strap.. A common but hard-to-find failure is the sensor's signal wire chafing against this ground strap, causing a short to ground. This results in a low voltage reading (e.g., code P2454) and can trigger performance codes like P1451, even with a perfectly good sensor and clean hoses.

Real Owner Repair Stories

• YouTube user detailing a P2454 fix (3rd Gen Ram with 6.7L Cummins) — Check Engine Light with DPF-related code (P2454, low sensor voltage).
  ❌ Tried (didn't work) Replacing the DPF differential pressure sensor.
  ✅ What actually fixed it The owner traced the sensor wiring harness forward from the sensor. He discovered the harness was rubbing against the transmission ground strap on the driver's side bell housing, which had worn through the insulation on the signal wire and caused a short to ground. Repairing the damaged wire and protecting the harness from future chafing resolved the code.

OEM Part Supersession History

• 68085750AA → 68085750AB — Standard part revision.
• 68312096AA → 68312096AB — Standard part revision.

Model Year Variations Within This Range

• 2019-2020: The DPF differential pressure sensor was changed to a new part number (68312096AB).
• 2018-2020: Introduction of the Security Gateway Module (SGW). This prevents aftermarket scan tools from performing bidirectional commands (like a forced regen or DPF reset) without a specific bypass cable or adapter that plugs into the CAN bus, often found under the dash near the light switch.