P20E3 – Exhaust Gas Temperature Sensor 1/3 Bank 1 Correlation

P20E3 Possible Causes

Faulty exhaust gas temperature sensor
Exhaust gas temperature sensor harness is open or shorted
Poor electrical connection in the exhaust gas temperature sensor circuit
Exhaust leaks
Excessive particulate buildup on the sensor

What Does It Mean?

How to Fix Code P20E3

Check the “possible causes” listed above. Visually inspect the wiring harness and related connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P20E3 Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P20E3 Meaning

The Powertrain Control Module (PCM) continuously monitors the Exhaust Gas Temperature Sensor (EGTS) for proper circuit continuity and out-of-range high values. The EGTS is located in front of the Diesel Oxidation Catalyst (DOC) and/or in front of the Diesel Particulate Filter (DPF). The EGTS detects exhaust gas temperature and converts it to voltage, sending it back to the PCM with the voltage signal to control engine conditions for effective emission reduction. The PCM sets the OBDII code P20E3 when the exhaust gas temperature sensor is outside factory specifications.

P20E4 – Exhaust Gas Temperature Sensor 2/3, Correlation, Bank 1

P20E4 Possible Causes

Faulty exhaust gas temperature sensor
Exhaust gas temperature sensor harness is open or shorted
Poor electrical connection in the exhaust gas temperature sensor circuit
Exhaust leaks
Excessive particulate buildup on the sensor

What Does It Mean?

How to Fix Code P20E4

P20E4 Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P20E4 Meaning

The powertrain control module (PCM) continuously monitors the exhaust gas temperature sensor (EGTS) for proper circuit continuity and out-of-range high values. The EGTS is located in front of the diesel oxidation catalyst (DOC) and/or in front of the diesel particulate filter (DPF). The EGTS detects exhaust gas temperature and converts it to voltage, sending it back to the PCM with the voltage signal to control engine conditions for effective emission reduction. The PCM sets the OBDII code P20E4 when the exhaust gas temperature sensor is outside factory specifications.

P20E5 – Exhaust Gas Temperature Sensor 1/2 Bank 2 Correlation

P20E5 Possible Causes

Faulty exhaust gas temperature sensor
Exhaust gas temperature sensor harness is open or shorted
Poor electrical connection in the exhaust gas temperature sensor circuit
Exhaust leaks
Excessive particulate buildup on the sensor

What Does It Mean?

How to Fix Code P20E5

P20E5 Possible Symptoms

Check engine light illuminated (or service engine soon warning light)

P20E5 Meaning

The Powertrain Control Module (PCM) continuously monitors the Exhaust Gas Temperature Sensor (EGTS) for proper circuit continuity and out-of-range high values. The EGTS is located in front of the Diesel Oxidation Catalyst (DOC) and/or in front of the Diesel Particulate Filter (DPF). The EGTS detects exhaust gas temperature and converts it to voltage, sending it back to the PCM with the voltage signal to control engine conditions for effective emission reduction. The PCM sets the OBDII code P20E5 when the exhaust gas temperature sensor is outside factory specifications.

P20E6 – Reductant Injection Air Pressure Too Low

How severe is this DTC?

A stored P20E6 code should be considered severe and addressed as soon as possible. The SCR system may be disabled because of this. Catalyst damage could occur if the conditions that led to the code being stored are not corrected in a timely manner.

What are some of the symptoms of the code?

Symptoms of a P20E6 fault code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What are some common causes of the code?

Causes

of this code may include:

Reductant injection air pressure too low
Faulty reductant injection air pressure sensor
Open or shorted circuits in the reductant injection air pressure sensor system
Faulty SCR controller/PCM or programming error

What are the troubleshooting steps for P20E6?

Ensure that the reductant supply/regeneration system is not losing pressure (internally or externally). Activate the pump to create pressure and inspect the system for external leaks. Use a fuel pressure tester to manually monitor the reductant system pressure. Check the supply pump and injector for leaks. If leaks are found (internal or external), they must be repaired before continuing diagnosis.

A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be required to diagnose a P20E6 code.

You can use your vehicle information source to locate a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it may provide helpful diagnostic information.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to note this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at this point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that led to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code immediately resets, the next step in your diagnosis will require you to search your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test the reductant injection system pressure sensors according to manufacturer specifications. Components that do not test within allowable parameters should be considered faulty.

Step 2

If reductant injection pressure meets specifications, the P20E6 code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the sensors and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant injector sensor codes are often attributed to internally leaking supply pumps

P20E7 – Reductant Injector Air Pressure Too High

How severe is this DTC?

A stored P20E7 code should be considered severe and addressed as quickly as possible. The SCR system may be disabled because of this. Catalyst damage could occur if the conditions that contributed to the code being stored are not corrected in a timely manner.

What are some of the symptoms of the code?

Symptoms of a P20E7 trouble code may include:

Reduced fuel efficiency
Excessive black smoke from the vehicle’s exhaust
Decreased engine performance
Other SCR-related codes

What are some common causes of the code?

Causes

of this code may include:

Reductant injection air pressure too high
Faulty reductant injection air pressure sensor
Open or shorted circuits in the reductant injection air pressure sensor system
Faulty SCR controller/PCM or programming error

What are the troubleshooting steps for P20E7?

Ensure the reductant supply/regeneration system is not losing pressure (internally or externally). Activate the pump to create pressure and inspect the system for external leaks. Use a fuel pressure tester to manually monitor the reductant system pressure. Check the supply pump and injector for leaks. If leaks are discovered (internal or external), they must be repaired before continuing diagnosis.

A diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information source will be needed to diagnose a P20E7 code.

If the PCM enters readiness mode at this point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

Step 1

Use the DVOM to test the reductant injection system pressure sensors according to manufacturer specifications. Components that do not test within allowable parameters should be considered faulty.

Step 2

If reductant injection pressure is within specifications, the P20E7 code persists, and the sensor in question is operational, use the DVOM to test the input and output signal circuits between the sensors and the PCM/SCR controller. Disconnect all controllers before using the DVOM for testing.

Reductant injector sensor codes are often attributed to internally leaking supply pumps

P20E8 – Pressure Reducer Pressure Too Low

What does the P20E8 code mean?

The P20E8 code indicates a problem in the system that reduces pollution in diesel engines. This system, called SCR (or DEF/AdBlue), uses a special fluid to reduce harmful emissions.
This error message appears when the reducer fluid pressure is too low, which prevents the system from functioning properly.

Possible symptoms:

The engine warning light illuminates on the dashboard
Possible warning messages related to emissions or AdBlue may appear

Common causes of the problem:

DEF pump faulty
Reducer fluid injector damaged
Purge valve of the system no longer working correctly
Hose or pipe of the reducer fluid punctured or clogged
Pressure sensor faulty

How to resolve the problem?

Visually inspect the cables and connectors related to the DEF system: look for cut wires, broken pins, or signs of corrosion.
Check the main components of the system: pump, injector, sensor, valve, and pipes.
If in doubt, a diagnosis with an OBD tool can help you precisely locate the fault.

🔧 Tip: This type of problem can prevent the proper functioning of the anti-pollution system and, eventually, limit the vehicle’s performance or prevent it from starting. Therefore, it is recommended to have the vehicle checked by a professional quickly.

P20E9 – Reductant Pressure Too High

P20E9 Possible Causes

Damaged reductant pump
Damaged reductant injector
Damaged reductant purge valve
Damaged reductant pressure line
Damaged reductant pressure sensor

What Does It Mean?

How to Fix P20E9 Code

Check the “possible causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

P20E9 Possible Symptoms

Engine light on (or service engine soon warning light)

P20E9 Meaning

The Powertrain Control Module (PCM) monitors the reductant pressure when the system is preparing for injection. The DEF post-treatment pump has internal diagnostics that assess whether the DEF pump is capable of meeting its demand. If the pump reports insufficient performance for more than a threshold time, the P20E8 code is set.

P20EA – Power Relay Shutdown Performance of the Gear Control Module Too Early

P20EA Possible Causes

Faulty reducer control module power relay
Reducer control module power relay circuit open or shorted
Poor electrical connection in reducer control module power relay circuit

What Does It Mean?

How to Fix Code P20EA

P20EA Possible Symptoms

Engine light on (or service engine soon warning light)

P20EA Meaning

Reducer control module power relay disabled performance too early is the generic description for code P20EA, but the manufacturer may have a different description.

P20EB – Power Relay Shut-Off Performance Too Late in Gear Control Module

P20EB Possible Causes

Defective power relay of the reduction gear control module
Open or short circuit in the power relay wiring harness of the reduction gear control module
Poor electrical connection in the power relay circuit of the reduction gear control module

What Does It Mean?

How to Fix Code P20EB

Check the “possible causes” listed above. Visually inspect the related cable harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.

P20EB

Possible Symptoms

Engine light on (or service engine soon warning light)

P20EB Meaning

The off-performance of the reduction gear control module power relay is too delayed is the generic description for code P20EB, but the manufacturer may have a different description.

P20EC – NOx SCR Catalyst – Overheating, Bank 1

How severe is this DTC?

All stored SCR-related codes can trigger SCR system deactivation. The stored P20EC code should be considered severe and addressed as quickly as possible. Catalyst damage could occur if the code is not corrected promptly.

What are some symptoms of the code?

Symptoms of a P20EC fault code may include:

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

What are some common causes of the code?

Causes of this code may include:

Faulty exhaust temperature sensor
Non-operational SCR system
Defective SCR injector
Incorrect or insufficient DEF fluid
Incorrect SCR controller or programming error
Pre-catalyst exhaust leaks
Installation of aftermarket or high-performance exhaust components

What are the troubleshooting steps for P20EC?

If other SCR or exhaust emission codes or exhaust temperature codes are stored, these should be addressed before attempting to diagnose the stored P20EC.

All pre-catalyst exhaust leaks must be repaired before attempting diagnosis for this type of code.

Access to a diagnostic scanner, digital volt/ohmmeter (DVOM), infrared thermometer with laser pointer, and vehicle-specific SCR system diagnostic information source will be necessary to diagnose a P20EC code.

Finding a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms could provide useful diagnostic information.

Begin your diagnosis with a visual inspection of the SCR injection system, exhaust temperature sensors, NOx sensors, and oxygen sensor (O2) harnesses and connectors. Burned or damaged wiring and/or connectors should be repaired or replaced before continuing.

Continue by locating the vehicle’s diagnostic connector and connecting the scanner. Retrieve all stored codes and relevant freeze frame data and record this information before clearing codes. Then test drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode, the code is intermittent and may be much more difficult to diagnose at this point. Conditions that contributed to code storage may need to worsen before diagnosis can be achieved.

If the code resets immediately, consult your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, as well as component testing procedures and specifications. This information will be needed to complete the next steps of your diagnosis.

Observe scanner data flow to compare exhaust temperature sensor data (pre and post catalyst) between engine banks. If inconsistencies are detected, test the exhaust temperature sensors using the DVOM. Sensors that do not meet manufacturer specifications should be considered defective.

If all sensors and circuits appear to be functioning as expected, suspect that the catalyst element is defective or the SCR system has failed.

Ensure the DEF tank is filled with appropriate fluid and has not been contaminated in any way