The P20AD: Reductant Metering Unit Temperature Sensor Circuit Range/Performance fault code indicates that the reductant metering unit temperature sensor is not operating within its expected range or performance parameters. This sensor monitors the temperature of the diesel exhaust fluid (DEF) to ensure accurate dosing. If the sensor is faulty or the circuit has issues, it can result in incorrect DEF dosing and emissions control problems. Common causes include incorrect sensor performance, a faulty temperature sensor, or sensor circuit problems.
P20AD – Quick Overview
Code | Information |
---|---|
Meaning | P20AD: Reductant Metering Unit Temperature Sensor Circuit Range/Performance |
Is it serious? | Yes, it can cause improper DEF dosing, leading to emissions control issues and potential system inefficiencies. |
Possible causes | – Incorrect sensor performance – Faulty temperature sensor – Sensor circuit problems |
How to diagnose? | – Test the sensor for range and performance – Inspect wiring and connectors – Check the sensor circuit |
P20AD Meaning
The P20AD code signifies that the reductant metering unit temperature sensor is not functioning correctly within the expected performance range. This sensor is crucial for monitoring the temperature of the diesel exhaust fluid (DEF) to ensure it is injected correctly into the exhaust system. Incorrect sensor performance can result in improper DEF injection, affecting emissions control and overall engine performance.
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 more information about the sensor circuit issue. | OBD-II Scanner |
Test the Sensor for Range/Performance | Use a multimeter or diagnostic tool to test the temperature sensor and verify that it is operating within the specified range and performing accurately. | Multimeter, Diagnostic Tool |
Inspect Wiring and Connectors | Visually inspect the wiring and connectors associated with the temperature sensor for any signs of damage, corrosion, or loose connections that could affect performance. | Flashlight, Multimeter |
Check the Sensor Circuit | Measure the voltage and resistance in the sensor circuit to ensure it is performing correctly and providing the necessary signals. | Multimeter, Circuit Tester |
Clear the Code and Test Drive | After repairs, clear the code using an OBD-II scanner and take the vehicle for a test drive to ensure the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | After the test drive, re-scan the vehicle to ensure the P20AD code does not return. If it reappears, further diagnostics may be required. | OBD-II Scanner |

OBD-II scanner Buyer’s Guide
- Scanner features explained
- Different types of scanners
- Scanners for coding/odometer/ECU/checks
- Best picks + discount codes

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)