The P20F4: Reductant Consumption Too Low fault code indicates that the vehicle’s reductant (Diesel Exhaust Fluid, DEF) consumption is lower than expected. This could affect the Selective Catalytic Reduction (SCR) system’s ability to reduce NOx emissions effectively. The issue may be caused by a faulty reductant injector or problems with the system’s calibration.
P20F4 – Quick Overview
Code | Information |
---|---|
Meaning | P20F4: Reductant Consumption Too Low |
Is it serious? | Yes, low reductant consumption can lead to inefficient NOx reduction, causing emissions control issues and possibly engine performance problems. |
Possible causes | – Reductant consumption lower than expected – Faulty reductant injector – Issues with reductant system calibration |
How to diagnose? | – Measure reductant consumption – Test the reductant injector – Check and calibrate the reductant system |
P20F4 Meaning
The P20F4 fault code indicates that the SCR system is consuming less reductant (DEF) than required to properly reduce NOx emissions. This can result in higher-than-allowed NOx levels in the vehicle’s exhaust, which can trigger emissions-related faults. The low reductant consumption may be due to a malfunctioning reductant injector, improper system calibration, or other issues in the reductant system.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional related codes that may provide further details about the reductant consumption issue. | OBD-II Scanner |
Measure Reductant Consumption | Compare the vehicle’s current reductant (DEF) consumption to manufacturer specifications using diagnostic software to determine if it is too low. | Diagnostic Tool |
Test the Reductant Injector | Use a diagnostic tool to test the reductant injector to ensure it is functioning properly and delivering the correct amount of reductant to the exhaust system. | Multimeter, Diagnostic Tool |
Inspect the Reductant System | Inspect the reductant delivery system for any blockages, leaks, or damage that may be preventing proper DEF injection. | Flashlight, Diagnostic Tool |
Check and Calibrate the Reductant System | Ensure that the reductant system is properly calibrated to inject the correct amount of DEF based on the engine load and emissions levels. Perform any necessary recalibration. | Calibration Tool |
Repair or Replace Faulty Components | If the reductant injector or any other components are found to be faulty, repair or replace them to restore proper reductant consumption. | Replacement Parts, Tools |
Clear the Code and Test Drive | After completing repairs, clear the code using an OBD-II scanner and test drive the vehicle to confirm that the issue is resolved. | OBD-II Scanner, Vehicle Manual |
Recheck for Codes | After the test drive, rescan the vehicle to ensure the P20F4 code does not return. | 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)