OBD-II Diagnostic Trouble Code
P2043 — Reductant Temperature Sensor Circuit Range/Performance
P2043 means the reductant (DEF) temperature sensor reading is electrically in range but not believable. The ECM compares it to other temperatures such as ambient and coolant after a cold soak, or watches for a reading that does not change as heating runs. The sensor is usually part of the DEF tank header or supply module.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
Reductant Temperature Sensor Circuit Range/Performance
Code
P2043
Category
Powertrain
Subsystem
Aftertreatment
Truck-relevant
Yes
What this means for truckers
P2043 (Reductant Temperature Sensor Range/Performance) — sensor reading is out of plausible range. Usually means sensor failure or wiring.
Before you replace parts — try this first
P2043 on the Aftertreatment system is most often temperature sensor drifting out of calibration in the def tank header or supply module — 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 warning and check-engine light, possible incorrect DEF heating in winter, and limited or disabled dosing. Many trucks start an emissions derate countdown. The truck may drive normally for a while.
Common causes
- CommonTemperature sensor drifting out of calibration in the DEF tank header or supply module ($700–$2000)
- CommonHigh resistance in the connector or wiring from DEF corrosion ($100–$350)
- OccasionalFrozen DEF or failed tank heater or coolant valve causing a reading that does not rise as expected ($150–$2000)
- OccasionalAmbient or coolant reference sensor actually being the bad sensor ($100–$350)
How to fix
After a cold soak, compare DEF, ambient, coolant and intake temperatures on a scan tool
When to use: First step to find which sensor disagrees
Check for voltage drop or corrosion at the DEF sensor connector
When to use: When the reading is offset but changes normally
Verify the tank heater and coolant valve work and the DEF thaws as expected
When to use: When the code sets in cold weather
Replace the DEF tank header or supply module assembly
When to use: When the sensor itself is confirmed out of specification
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 P2043?
P2043 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 P2043 on a commercial truck?
Total repair cost ranges $100–$2000 depending on the root cause. The cheapest fix is usually the first one listed below — Temperature sensor drifting out of calibration in the DEF tank header or supply module — 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 P2043 fail a DOT inspection?
Yes — P2043 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 P2043 and related codes?
P2043 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 P2043 is set without the companions, the issue is more isolated.
How do I prevent P2043 from coming back after a repair?
For P2043 (Reductant Temperature Sensor Circuit Range/Performance), 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).