Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / P2000 — NOx Trap Efficiency Below Threshold (Bank 1)

P2000 — NOx Trap Efficiency Below Threshold (Bank 1)

Detailed page for trouble code P2000.

34,480codes
59brands
11,925generic
22,555specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

P2000

MERCEDES-BENZ P — Powertrain

NOx Trap Efficiency Below Threshold (Bank 1)

Brand: MERCEDES-BENZ
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Degraded or saturated NOx trap/catalyst on Bank 1
  • Faulty NOx sensor (upstream or downstream) or sensor heater
  • Exhaust leak upstream of the NOx sensor or catalyst
  • Fuel injection problems (incorrect fueling, injector leak or clog) causing wrong exhaust composition
  • EGR or boost control faults changing NOx formation
  • Ignition timing or misfire causing abnormal exhaust

Symptoms

  • Malfunction Indicator Lamp (MIL/Check Engine) illuminated
  • Poor emissions performance or failed emissions test
  • Possible degraded fuel economy
  • Occasional rough idle or reduced drivability if root cause affects combustion
  • Possible regeneration requests or limp-home behavior on some vehicles

What to check

  • Read freeze frame and live data (NOx sensor outputs, catalyst temps, fuel trims, misfire counts)
  • Inspect exhaust from manifold to NOx sensor/catalyst for leaks, damage or rust
  • Visually inspect wiring and connectors for corrosion, heat damage, or disconnection
  • Check upstream/downstream NOx sensor signals and heater operation
  • Check oxygen sensors and short/long term fuel trims for abnormal values
  • Scan for related codes (misfires, fuel system, EGR, boost control)

Signal parameters

  • NOx sensor concentration (ppm or ppb) upstream and downstream
  • NOx trap conversion efficiency (%) or delta NOx across trap
  • NOx sensor heater circuit status / resistance (Ω)
  • Catalyst/NOx trap temperature (°C)
  • Upstream O2 sensor voltage and lambda
  • Short-term and long-term fuel trim (%)

Diagnostic algorithm

  1. Retrieve freeze-frame data and all stored codes. Confirm P2000 is current and note related codes.
  2. Verify proper operation of the NOx sensor heater (resistance and commanded on/off) and check for DTCs for heater circuit.
  3. Monitor live data: compare upstream and downstream NOx readings and trap temperature during various loads; note if downstream NOx remains high.
  4. Inspect exhaust system for leaks between engine and NOx sensor/catalyst; repair any leaks and retest.
  5. Check fuel system and combustion: review fuel trims, lambda/O2 sensor behavior, and misfire counts. Diagnose and repair any injector, ignition, or fuel supply issues.
  6. Inspect wiring and connectors to NOx sensors for continuity, shorts to ground, or corrosion; repair as needed.
  7. If sensors and engine operation are good, consider NOx trap condition: perform diagnostic regeneration cycle if serviceable per manufacturer procedures, then re-evaluate NOx conversion.
  8. If regeneration not possible or trap remains inefficient after proper engine/sensor repairs, replace NOx trap/catalyst and/or faulty NOx sensors as indicated.
  9. After repairs, clear codes and perform road test with live data capture to confirm NOx trap efficiency returns to expected thresholds and code does not return.

Likely causes

  • NOx sensor failure (incorrect NOx concentration readings)
  • NOx trap is chemically poisoned or physically degraded
  • Exhaust leak between engine and NOx sensor/catalyst
  • High short-term fuel trim or persistent misfire altering NOx production
  • Faulty sensor heater preventing correct operating temperature

Fault status

⚠️ Status
NOx Trap Efficiency Below Threshold (Bank 1) — control module has detected insufficient NOx conversion across the NOx storage/reduction catalyst on bank 1. Possible sensor, catalyst, exhaust leak, or combustion-related causes.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.5 hours

Similar codes

P2001 P0420 P2195 P2196 P2201
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MERCEDES-BENZ

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .