SPN 3055 – DPF Differential Pressure Sensor Fault (2025 Full Fix Guide)

SPN 3055 – DPF Differential Pressure Sensor Fault (2025 Full Fix Guide)

If your truck shows SPN 3055 or DPF pressure abnormal, you are dealing with one of the top causes of regen failure, high soot levels, and derates across all diesel engines.

This is one of the MOST common aftertreatment problems on:

  • Cummins ISB / ISX / X15

  • Detroit DD13 / DD15 / DD16

  • Paccar MX-13

  • Volvo / Mack

  • International A26

  • Duramax / Powerstroke

  • Medium-duty trucks

DPF differential pressure determines how full the DPF is.
If the reading is incorrect → the ECM blocks regen → soot skyrockets → derate hits.

The good news?
SPN 3055 is almost always an easy fix — if you diagnose properly.

🚨 What Does SPN 3055 Mean?

SPN 3055 = DPF Differential Pressure Sensor Voltage Out of Range

The ECM sees the wrong pressure reading across the DPF.

This can indicate:

  • True DPF restriction

  • Sensor clogging

  • Pressure tube blockage

  • Water contamination

  • Sensor voltage circuit fault

  • Cracked pressure lines

Without accurate pressure, the ECM cannot perform a regen.

⚠️ Symptoms of SPN 3055

  • Frequent regens

  • Regen won’t complete

  • Regen won’t start

  • High soot level (SPN 3719)

  • SPN 5246 (derate)

  • “Service Exhaust Filter”

  • Poor fuel economy

  • Power loss

  • Unstable exhaust temperature

  • Loud fan running non-stop

This code always affects regen performance.

🔍 Real Causes of SPN 3055 (Ranked by Frequency)

1. Clogged Pressure Tubes (MOST COMMON – 60% of failures)

Soot and moisture accumulate in the pressure lines.

Blockages cause:

  • High pressure readings at idle

  • Zero pressure at load

  • Erratic fluttering values

  • Regen failure

Cleaning the tubes fixes this in most cases.

2. Failed DPF Differential Pressure Sensor

The sensor itself may be reading:

  • Too high

  • Too low

  • Voltage out of range

  • Stuck values

This is the second most common SPN 3055 cause.

3. Water in Pressure Tubes

Condensation collects in cold climates.

Symptoms:

  • Pressure reading spikes

  • Regen aborted

  • Soot level increases instantly

4. Cracked or Leaking Pressure Lines

If a line is cracked:

  • Pressure reads too low

  • ECM thinks DPF is empty

  • Regen refuses to start

5. Actual Restriction in the DPF

If the DPF is really clogged:

  • Pressure skyrockets under load

  • Soot level rises rapidly

  • SPN 3719 appears

  • Regen fails repeatedly

6. Wiring Problems

Especially with Cummins, Detroit, Paccar.

Check for:

  • Corrosion

  • Broken pins

  • Rodents

  • Loose connectors

  • Sensor harness rubbing

❌ What NOT to Do for SPN 3055

❌ Don’t replace the DPF immediately

It’s almost NEVER the real issue.

❌ Don’t rely on a basic OBD reader

You MUST graph pressure under load.

❌ Don’t clear the code without fixing root cause

It will come back instantly.

❌ Don’t attempt regen until pressure is corrected

Regen will fail every time.

🛠️ How to Diagnose SPN 3055 (Dealer-Level Process)

You must use:

  • JPRO

  • Diesel Tech

  • Cummins Insite

  • Detroit DDDL

  • Paccar Davie

  • Volvo Tech Tool

These show:

  • Idle pressure

  • Load pressure

  • Temperature stability

  • Soot levels

  • DPF restriction

⭐ STEP 1 — Read DPF Pressure at Idle

Normal idle pressure:

👉 0.2 – 1.0 PSI

If idle pressure is:

  • Over 1.5 PSI → clogged tubes or sensor

  • 0.0 PSI → sensor/tube leak

⭐ STEP 2 — Read DPF Pressure Under Load

Normal load pressure:

👉 2 – 5 PSI

If pressure is:

  • Too high → DPF possibly restricted

  • Near zero → sensor or tube leak

  • Erratic / jumping → water or soot blockage

⭐ STEP 3 — Inspect Tubes for Soot or Moisture

Remove tubes and check for:

  • Soot plugs

  • Wet sludge

  • Condensation water

Clean or replace as needed.

⭐ STEP 4 — Test Sensor Voltage in Software

Look for:

  • Voltage stuck

  • No response to RPM changes

  • Signal dropouts

Bad readings = replace sensor.

⭐ STEP 5 — Check Wiring & Connector Pins

Common failures:

  • Green corrosion

  • Broken lock tab

  • Pin pushed out

  • Harness rubbing frame

⭐ STEP 6 — Run a Forced Regen

Once pressure is normal:

  • Run forced regen

  • Validate DPF temperatures

  • Confirm soot % drops

  • Confirm pressure curve stabilizes

💻 Tools You Need to Fix SPN 3055 Properly

You MUST have:

✔ Diesel diagnostic laptop

✔ Nexiq USB-Link 3

✔ Ability to read pressure graphs

✔ Ability to run forced regen

✔ Ability to reset differential pressure sensor

DieselScanners kits include all of this:

  • DPF pressure testing

  • Aftertreatment resets

  • Forced regen

  • Soot load monitoring

  • Live graphing

  • Lifetime support

📞 Need help picking the right kit? Call: (800) 987-4850

💲 Why SPN 3055 Misdiagnosis Costs Truck Owners Thousands

Shops typically replace:

❌ DPF ($1,500–$3,000)
❌ DEF pump ($900–$1800)
❌ EGT sensors ($200–$400 each)
❌ Pressure sensor ($250–$450)
❌ Tubes ($60–$120)
❌ Diagnostic time ($300–$500)

When the real issue is usually:

  • Cleaning a blocked tube

  • Replacing a $200 sensor

  • Fixing wiring

Your diesel laptop prevents all unnecessary repairs.

🚛 Fix SPN 3055 Before It Causes a Full Derate

If ignored, SPN 3055 leads to:

  • Failed regens

  • Soot overload (SPN 3719)

  • SPN 5246 (derate)

  • 5 MPH limit

  • DPF cracking

  • Turbo overheating

Fix it now with DieselScanners.

📞 Call: (800) 987-4850
👉 Shop DieselScanners Diagnostic Kits

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