OBD2 - P20EE
OBD2 Error Codes

P20EE OBD2 error code - SCR NOx catalyst efficiency below threshold, bank 1

26.05.2022 /

DTC P20EE - OBD-II Data Sheet

P20EE OBD2 Error Code - SCR NOx Catalyst Efficiency Below Threshold Bank 1

What does the OBD2 code - P20EE mean?

This is a generic Diagnostic Trouble Code (DTC) applicable to many OBD-II vehicles (1996 and newer). This may include, but is not limited to, Audi, Buick, Chevrolet, Ford, GMC, Mercedes-Benz, Subaru, Toyota, Volkswagen, etc. Although the general repair steps may vary depending on the year of manufacture, make, model and transmission configuration. ...

When P20EE is stored in an OBD-II equipped diesel vehicle, it means that the powertrain control module has detected that the catalyst efficiency is below a threshold for a certain engine range. This particular code applies to the catalytic converter (or NOx trap) for the first bank of engines. Bank one is the engine group that contains the number one cylinder.

Although modern clean combustion diesel engines have many advantages over gasoline engines (especially in commercial trucks), they also tend to emit more certain harmful exhaust gases than other engines. The most prominent of these corrosive pollutants are nitrogen oxide (NOx) ions.

Exhaust Gas Recirculation (EGR) systems help dramatically reduce NOx emissions, but many of today's powerful diesel engines cannot meet stringent US federal (US) emission standards using the EGR system alone. For this reason, SCR systems have been developed.

SCR systems inject Diesel Exhaust Fluid (DEF) into the exhaust gases upstream of the catalytic converter or NOx trap. The introduction of DEF raises the temperature of the exhaust gases and allows the catalytic element to operate more efficiently. This extends catalyst life and reduces NOx emissions.

Oxygen (O2) sensors, NOx sensors and / or temperature sensors are placed before and after the catalyst to monitor its temperature and efficiency. The entire SCS system is controlled by either the PCM or a stand-alone controller that communicates with the PCM. Otherwise, the controller monitors the O2, NOx and temperature sensors (as well as other inputs) to determine the appropriate timing for the DEF injection. Precision DEF injection is essential to keep the exhaust gas temperature within acceptable parameters and to ensure optimal NOx filtration.

If the PCM detects that the catalyst efficiency is insufficient for the minimum acceptable parameters, a P20EE code will be stored and the malfunction indicator lamp may illuminate.

P20EE SCR NOx Catalyst Efficiency Below Threshold Bank 1

What is the severity of the p20ee DTC?

Any stored SCR-related codes may cause the SCR system to shut down. Stored P20EE code should be treated as serious and should be repaired as soon as possible. If the code is not corrected quickly, it may damage the catalytic converter.

What are some of the symptoms of the code?

Symptoms of a P20EE trouble code may include:

  • Excessive black smoke from vehicle exhaust
  • Reduced engine performance
  • Decreased fuel efficiency
  • Other stored SCR and emission codes

What are some of the common causes of the P20EE code?

Reasons for this code may include:

  • Defective O2, NOx or temperature sensor
  • Broken SCR system
  • Defective SCR injector
  • Incorrect or insufficient DEF fluid
  • Bad diesel particulate filter (DPF)
  • Exhaust leaks
  • Fuel contamination
  • Bad SCR controller or programming error
  • Exhaust leaks in front of the catalyst
  • Installation of non-original or high-performance exhaust system components

Diagnosing the causes of the OBD2 code - P20EE

To diagnose DTC P20EE, a technician must:

  1. Scan the codes in the ECM and look at the freeze frame data for trouble codes.
  2. Review vehicle history reports for previously set NOx related codes.
  3. Check for visible smoke from the exhaust pipe and inspect the exhaust system for leaks or damage.
  4. Check the hose fittings to make sure there are no obstructions.
  5. Inspect the exterior of the DPF or SCR catalytic converter for an extinguished flame or obvious signs of damage.
  6. Inspect the DEF fill tube for leaks, cap integrity, and proper fit of cap to fluid line.
  7. Check the status of the DTC in the ECM to ensure that the SCR system is enabled.
  8. Check key engine parameters for signs of damage or excessive fuel consumption due to injector misfire or turbo boost failure.

What are the troubleshooting steps for P20EE?

If other SCR or exhaust emission codes or exhaust gas temperature codes are stored, they should be cleared before attempting to diagnose the stored P20EE.

Any exhaust leaks in front of the catalytic converter must be repaired before attempting to diagnose this type of code.

Diagnosing a P20EE code will require access to a diagnostic scanner, digital volt / ohmmeter (DVOM), infrared thermometer with laser pointer, and a source of diagnostic information for your specific SCR system.

Search for a Technical Service Bulletin (TSB) that matches the year of manufacture, make and model of the vehicle; as well as engine displacement, stored codes, and detected symptoms can provide useful diagnostic information.

Begin the diagnosis by visually inspecting the SCR injection system, exhaust gas temperature sensors, NOx sensors, and oxygen sensor harnesses and connectors (02). Burnt or damaged wiring and / or connectors must be repaired or replaced before proceeding.

Then find the car diagnostic connector and plug in the scanner. Retrieve all stored codes and associated freeze frame data and write this information down before clearing codes. Then test drive the vehicle until the PCM enters readiness mode or the code is cleared.

If the PCM does enter ready mode, the code is intermittent and can be much more difficult to diagnose at this time. The conditions that contributed to the persistence of the code may need to worsen before a diagnosis can be made.

If the code resets immediately, search your vehicle information source for diagnostic block diagrams, connector pinouts, connector faces, and component test procedures and specifications. This information will be needed to complete the next steps in your diagnosis.

Observe the data flow of the scanner to compare the readings of the exhaust gas sensors (before and after cleaning) O2, NOx and temperatures between the engine blocks. If inconsistencies are found, check the corresponding sensors using the DVOM. Sensors that do not meet the manufacturer's specifications should be considered defective.

If all sensors and circuits are working properly, suspect that the catalytic element is defective or that the SCR system is out of order.

Common P20EE Troubleshooting Mistakes

The following are some of the most common mistakes a technician can make when diagnosing a P20EE code:

What repairs can fix code P20ee?

Below are solutions that can fix this problem:

Related OBD2 error codes:

P20EE is associated with and may be accompanied by the following codes:

Hack and predictor Aviator

In conclusion, code P20EE is a DTC that is related to the SCR NOx Catalyst Efficiency Under Threshold fault. This can be caused by a number of issues, but the most common culprits are problems with the DPF filter element and DEF fluid. A technician should check these potential causes and check the service manual to properly diagnose and fix this code.

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