OBD-II Diagnostic Trouble Code
P2000 — NOx Trap Efficiency Below Threshold Bank 1
P2000 means NOx trap (lean NOx trap or NOx adsorber) efficiency is below the threshold on bank 1. The ECM saw from the downstream NOx sensor that the trap was not storing or reducing enough NOx. It applies to engines with a NOx adsorber, such as some 2007-2012 light and medium-duty diesels; most heavy trucks use SCR and report low NOx conversion with other codes.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
NOx Trap Efficiency Below Threshold Bank 1
Code
P2000
Category
Powertrain
Subsystem
Aftertreatment
Truck-relevant
Yes
What this means for truckers
P2000 — see existing entry.
Before you replace parts — try this first
P2000 on the Aftertreatment system is most often aged or sulfur-poisoned nox trap — 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
Check-engine light, possible derate on some trucks, more frequent NOx purge or desulfation events and possibly higher fuel use. Many trucks drive normally.
Common causes
- CommonAged or sulfur-poisoned NOx trap ($2000–$6000)
- CommonFaulty NOx sensor ($400–$1000)
- OccasionalExhaust leak before the sensor ($150–$600)
- OccasionalIncorrect fueling or failed purge/desulfation events ($200–$1500)
How to fix
Check NOx sensor readings and for exhaust leaks
When to use: First step
Perform a desulfation or forced regen if supported
When to use: When the trap may be sulfur-poisoned
Replace the NOx sensor
When to use: When the sensor reads wrong
Replace the NOx trap
When to use: When the catalyst is confirmed failed
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 P2000?
Drive with caution. P2000 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P2000 on a commercial truck?
Total repair cost ranges $150–$6000 depending on the root cause. The cheapest fix is usually the first one listed below — Aged or sulfur-poisoned NOx trap — 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 P2000 fail a DOT inspection?
Yes — P2000 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 P2000 and related codes?
P2000 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 P2000 is set without the companions, the issue is more isolated.
How do I prevent P2000 from coming back after a repair?
For P2000 (NOx Trap Efficiency Below Threshold Bank 1), 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).