The P203C: Reductant Level Sensor Circuit Low code indicates that the voltage in the reductant (DEF/AdBlue) level sensor circuit is lower than expected. This could be caused by a faulty sensor, wiring or connector problems, or issues within the sensor’s circuit.
P203C – Quick Overview
Code | Information |
---|---|
Meaning | P203C: Reductant Level Sensor Circuit Low |
Is it serious? | Yes, incorrect reductant level readings can lead to insufficient DEF supply, affecting NOx reduction and resulting in higher emissions. |
Possible causes | – Low voltage in the sensor circuit – Faulty sensor – Wiring or connector issues |
How to diagnose? | – Measure voltage in the sensor circuit – Test the sensor – Inspect wiring and connectors |
P203C Meaning
The P203C: Reductant Level Sensor Circuit Low code indicates that the voltage in the circuit for the reductant (DEF) level sensor is below the manufacturer’s specified range. This sensor monitors the DEF level in the tank to ensure the vehicle has enough fluid to reduce NOx emissions. A low voltage condition may result in inaccurate level readings, which could prevent the proper operation of the emissions system.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for any other codes related to the DEF system. Other codes may help provide additional insights into the source of the problem. | OBD-II Scanner |
Measure Voltage in the Sensor Circuit | Use a multimeter to measure the voltage in the reductant level sensor circuit. Compare the readings to the manufacturer’s specifications to confirm whether the voltage is indeed too low. | Multimeter |
Test the Reductant Level Sensor | Use a diagnostic tool or multimeter to test the reductant level sensor for proper function. If the sensor is malfunctioning, it may be providing incorrect readings and need to be replaced. | Diagnostic Tool, Multimeter |
Inspect Wiring and Connectors | Visually inspect all wiring and connectors leading to the sensor for damage, corrosion, or loose connections that could be causing a low voltage issue in the circuit. | Flashlight, Multimeter |
Check Sensor Circuit Continuity | Perform a continuity test on the sensor wiring. Look for shorts, breaks, or high resistance that could be affecting the sensor’s voltage readings. | Multimeter |
Inspect the Reductant Tank | Check the reductant (DEF) tank for any leaks, damage, or contamination that could affect the level sensor’s performance. Make sure the tank is functioning as expected. | Flashlight |
Replace the Reductant Level Sensor | If the level sensor is determined to be faulty or providing incorrect readings, replace it with a new sensor. Ensure proper installation to avoid future issues. | Replacement Sensor, Wrench |
Repair or Replace Damaged Wiring | If any wiring, connectors, or circuit components are damaged, repair or replace them to restore proper function and voltage levels in the sensor circuit. | Wiring Repair Kit |
Clear the Code and Test Drive | After completing repairs, clear the P203C code using an OBD-II scanner. Take the vehicle for a test drive to confirm that the issue is resolved and the sensor is functioning correctly. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | After the test drive, re-scan the vehicle to verify that the P203C code has not returned. | OBD-II Scanner |

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