The P204C: Reductant Pressure Sensor Circuit Low code indicates that the voltage in the reductant (DEF/AdBlue) pressure sensor circuit is lower than expected. This issue could be caused by low voltage in the circuit, a faulty sensor, or problems with wiring and connectors.
P204C – Quick Overview
| Code | Information |
|---|---|
| Meaning | P204C: Reductant Pressure Sensor Circuit Low |
| Is it serious? | Yes, low voltage can prevent proper DEF system operation, leading to poor NOx reduction and increased 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 |
P204C Meaning
The P204C: Reductant Pressure Sensor Circuit Low code indicates that the pressure sensor in the reductant system is reporting a lower voltage than expected. The pressure sensor monitors the DEF system to ensure proper fluid delivery for NOx reduction. If the voltage in the sensor circuit is too low, the sensor may not function correctly, affecting DEF injection and emissions control.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional related codes in the DEF system. These may help pinpoint related issues in the system. | OBD-II Scanner |
| Measure Voltage in the Sensor Circuit | Use a multimeter to measure the voltage in the reductant pressure sensor circuit. Compare the voltage readings with manufacturer specifications to verify if the voltage is too low. | Multimeter |
| Test the Reductant Pressure Sensor | Use a diagnostic tool or multimeter to test the sensor’s operation. Compare the sensor’s output with manufacturer specifications to determine if it is faulty. | Multimeter, Diagnostic Tool |
| Inspect Wiring and Connectors | Visually inspect all wiring and connectors leading to the reductant pressure sensor for damage, corrosion, or loose connections that may be causing a low voltage issue. | Flashlight, Multimeter |
| Perform Circuit Continuity Test | Perform a continuity test on the sensor circuit wiring to check for any breaks, shorts, or high resistance that may be causing low voltage in the circuit. | Multimeter |
| Inspect the DEF System | Check the DEF system for blockages, leaks, or contamination that could affect the sensor’s performance or cause low voltage readings. Ensure proper system operation. | Flashlight |
| Replace the Reductant Pressure Sensor | If the sensor is faulty or not providing the correct voltage, replace it with a new one. Ensure proper installation to prevent further issues. | Replacement Sensor, Wrench |
| Repair or Replace Damaged Wiring | Repair or replace any damaged wiring or connectors that may be causing the low voltage issue in the sensor circuit. | Wiring Repair Kit |
| Clear the Code and Test Drive | After completing repairs, clear the P204C code using an OBD-II scanner. Test drive the vehicle 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 verify that the P204C code has been cleared and 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)