The P204B: Reductant Pressure Sensor Circuit Range/Performance code indicates that the reductant (DEF/AdBlue) pressure sensor is not performing within its expected range. This issue can be caused by a faulty sensor, poor performance, or problems with wiring and connectors.
P204B – Quick Overview
Code | Information |
---|---|
Meaning | P204B: Reductant Pressure Sensor Circuit Range/Performance |
Is it serious? | Yes, incorrect sensor performance can lead to improper DEF injection, resulting in poor NOx reduction and increased emissions. |
Possible causes | – Faulty reductant pressure sensor – Incorrect sensor performance – Wiring or connector issues |
How to diagnose? | – Test the sensor for range and performance – Inspect wiring and connectors – Verify sensor operation |
P204B Meaning
The P204B: Reductant Pressure Sensor Circuit Range/Performance code signifies that the DEF pressure sensor is providing readings outside the expected range, either too high or too low. The sensor monitors the pressure in the DEF system to ensure proper delivery of fluid for NOx reduction. If the sensor is malfunctioning or if there are issues in the circuit, the DEF system may not operate properly.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional codes related to the DEF system or emissions control. These may provide more context for diagnosing the issue. | OBD-II Scanner |
Test the Reductant Pressure Sensor | Use a diagnostic tool or multimeter to test the performance and range of the pressure sensor. Compare the readings to the manufacturer’s specifications to determine if the sensor is operating correctly. | Multimeter, Diagnostic Tool |
Inspect Wiring and Connectors | Visually inspect all wiring and connectors leading to the reductant pressure sensor. Look for any signs of damage, corrosion, or loose connections that could affect the sensor’s performance. | Flashlight, Multimeter |
Check Sensor Circuit Continuity | Perform a continuity test on the wiring connected to the pressure sensor. Check for any shorts, breaks, or high resistance that could affect the sensor’s operation. | Multimeter |
Inspect the DEF System | Check the DEF system for any blockages, leaks, or contamination that may affect the pressure sensor’s performance. Ensure the system components are working properly. | Flashlight, Pressure Gauge |
Replace the Reductant Pressure Sensor | If the sensor is determined to be faulty or performing outside the expected range, replace it with a new sensor. Ensure proper installation to prevent further issues. | Replacement Sensor, Wrench |
Repair or Replace Damaged Wiring | Repair or replace any faulty wiring, connectors, or components that are causing the pressure sensor to operate outside its expected range. | Wiring Repair Kit |
Clear the Code and Test Drive | After repairs are made, clear the P204B code using an OBD-II scanner. Take the vehicle for a test drive to confirm that the sensor is working correctly and the issue is resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | After the test drive, re-scan the vehicle to ensure that the P204B code has been cleared and that the system is functioning properly. | OBD-II Scanner |

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Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)