OBD-II Diagnostic Trouble Code
P2044 — Reductant Temperature Sensor Circuit Low
P2044 means the reductant (DEF) temperature sensor signal is below its expected voltage range. Usually the signal circuit is shorted to ground or the sensor is shorted internally, giving a reading the ECM knows is impossible. The sensor is typically inside the DEF tank header unit or supply module.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Reductant Temperature Sensor Circuit Low
Code
P2044
Category
Powertrain
Subsystem
Aftertreatment
Truck-relevant
Yes
What this means for truckers
P2044 (Reductant Temperature Sensor Low) — sensor shorted to ground. Replace sensor.
Before you replace parts — try this first
P2044 on the Aftertreatment system is most often signal wire shorted to ground in the def harness — 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
DEF/SCR warning and check-engine light, DEF heating control may run incorrectly or not at all, and dosing can be disabled, leading to an emissions derate countdown.
Common causes
- CommonSignal wire shorted to ground in the DEF harness ($100–$400)
- CommonShorted temperature sensor in the tank header or supply module ($700–$2000)
- OccasionalDEF contamination in the connector creating a leak path to ground ($100–$350)
- RareControl module input fault ($1000–$3000)
How to fix
Unplug the sensor connector and see if the reading goes to an open-circuit value
When to use: To separate a sensor short from a wiring short
Check the signal wire for continuity to ground with both ends unplugged
When to use: When the reading stays low with the sensor disconnected
Clean and seal the connector
When to use: When DEF crystals or corrosion are visible
Replace the DEF tank header or supply module assembly
When to use: When sensor resistance is confirmed low
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
- → P2002 — Diesel Particulate Filter Efficiency Below Threshold (Bank 1)
- → P2003 — Diesel Particulate Filter Efficiency Below Threshold (Bank 2)
- → P2031 — Exhaust Gas Temperature Sensor Bank 1 Sensor 2
- → P2032 — Exhaust Gas Temperature Sensor Bank 1 Sensor 2 Low
- → P2033 — Exhaust Gas Temperature Sensor Bank 1 Sensor 2 High
Frequently Asked Questions
Can I drive with code P2044?
P2044 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 P2044 on a commercial truck?
Total repair cost ranges $100–$3000 depending on the root cause. The cheapest fix is usually the first one listed below — Signal wire shorted to ground in the DEF harness — 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 P2044 fail a DOT inspection?
Yes — P2044 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 P2044 and related codes?
P2044 is closely related to: P2002 (Diesel Particulate Filter Efficiency Below Threshold (Bank 1)), P2003 (Diesel Particulate Filter Efficiency Below Threshold (Bank 2)), P2031 (Exhaust Gas Temperature Sensor Bank 1 Sensor 2), P2032 (Exhaust Gas Temperature Sensor Bank 1 Sensor 2 Low). 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 P2044 is set without the companions, the issue is more isolated.
How do I prevent P2044 from coming back after a repair?
For P2044 (Reductant Temperature Sensor Circuit 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).