Reductant Pressure Sensor Circuit High
The P204D code indicates that the reductant (DEF) pressure sensor circuit is reading a voltage higher than the expected range. This sensor monitors the pressure in the DEF delivery system to ensure proper injection into the exhaust stream. A high voltage signal can be caused by a faulty sensor, wiring issues, or a malfunctioning DEF pump. This condition can lead to incorrect DEF dosing, potentially causing increased emissions and triggering the check engine light.
1. Most Common Causes
- Faulty reductant pressure sensor
- Short to voltage in sensor circuit
- Corroded or damaged wiring/connectors
- Defective DEF pump or control module
2. Symptoms You Will Notice
- Check engine light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to read the live data from the reductant pressure sensor and compare to manufacturer specifications.
Step 2: Visually inspect the sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor circuit for shorts to voltage using a multimeter.
Step 4: If sensor and wiring are okay, test the DEF pump operation and pressure output.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause reduced performance and increased emissions. The vehicle may enter limp mode to protect the engine.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and sensor replacement, but can be higher if the DEF pump or module needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.