OBD-II Diagnostic Trouble Code
P244A — Diesel Particulate Filter Differential Pressure Too Low
The ECM saw a DPF differential pressure, measured across the filter, that is lower than expected for the current exhaust flow. Low delta pressure usually means exhaust is bypassing the filter, because the substrate is cracked or melted or the sensor lines are disconnected. It can also mean the filter is missing, or the sensor is reading wrong.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Diesel Particulate Filter Differential Pressure Too Low
Code
P244A
Category
Powertrain
Subsystem
Aftertreatment
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P244A on the Aftertreatment system is most often cracked or melted dpf substrate from an uncontrolled regen or engine oil or fuel contamination — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
The check-engine light comes on, often with an emissions-related derate on heavy trucks after repeated detections. Black soot may show at the tailpipe if the DPF is cracked. Regen scheduling may be affected, and the truck may fail an opacity test.
Common causes
- CommonCracked or melted DPF substrate from an uncontrolled regen or engine oil or fuel contamination ($2500–$6500)
- CommonDisconnected, cracked or plugged differential pressure sensor hose ($50–$250)
- OccasionalFaulty differential pressure sensor reading low ($150–$500)
- OccasionalExhaust leak upstream of the DPF inlet pressure tap ($150–$600)
How to fix
Inspect the differential pressure sensor hoses and tubes for cracks, disconnections, melting and soot plugging
When to use: First step
Compare sensor readings at key-on engine-off (should be near zero) and at high idle against OEM values
When to use: To decide whether the problem is the sensor or the filter
Remove the DPF and inspect the outlet face for soot streaks or cracked cells
When to use: When sensor and lines check good, or there is soot at the tailpipe
Replace the DPF and investigate the root cause of the failure, such as a failed injector, a turbo oil leak or an aborted regen
When to use: When the substrate is damaged
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P244B — Diesel Particulate Filter Differential Pressure Too High
- → P244C — Exhaust Gas Temperature Too Low Bank 1
- → P244D — Exhaust Gas Temperature Too High Bank 1
- → P245A — EGR Cooler Bypass Control Circuit/Open
- → P246E — Particulate Filter Active/Intrusive Injection Quantity Too Low Bank 1
Frequently Asked Questions
Can I drive with code P244A?
P244A is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P244A on a commercial truck?
Total repair cost ranges $50–$6500 depending on the root cause. The cheapest fix is usually the first one listed below — Cracked or melted DPF substrate from an uncontrolled regen or engine oil or fuel contamination — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P244A fail a DOT inspection?
Yes — P244A is an emissions-related code, and DOT inspectors check emissions compliance. An active emissions code with a check engine light can result in an out-of-service violation under FMCSA Part 393. The truck typically can't be moved until the code is cleared. Repeated emissions violations escalate to CSA scores.
What's the difference between P244A and related codes?
P244A is closely related to: P244B (Diesel Particulate Filter Differential Pressure Too High), P244C (Exhaust Gas Temperature Too Low Bank 1), P244D (Exhaust Gas Temperature Too High Bank 1), P245A (EGR Cooler Bypass Control Circuit/Open). These codes share the same subsystem (aftertreatment) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P244A is set without the companions, the issue is more isolated.
How do I prevent P244A from coming back after a repair?
For P244A (Diesel Particulate Filter Differential Pressure Too Low), prevention centers on the aftertreatment system. Run quality DEF (verify supplier — BlueDEF, PEAK, Yara Air1). Don't skip parked regens — when the dash asks for one, do it. Avoid extended idle time which fouls the DPF. Replace NOx sensors at the OEM interval (typically 400K miles).