Reductant Pressure Sensor Circuit Range/Performance
The P204B code indicates that the reductant (DEF) pressure sensor circuit is reporting a signal that is outside the expected range or not performing correctly. This sensor monitors the pressure in the DEF delivery system to ensure proper injection into the exhaust stream. The Powertrain Control Module (PCM) detects that the sensor voltage or frequency is not within the calibrated range, which can lead to incorrect DEF dosing and potential emissions issues.
01. Most Common Causes
- Faulty reductant pressure sensor
- Wiring or connector issues in the sensor circuit (open, short, corrosion)
- DEF pump malfunction causing incorrect pressure
- Blocked or leaking DEF lines
- PCM software or hardware failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased DEF consumption or no DEF injection
- Possible diesel exhaust fluid (DEF) warning messages on dashboard
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes (e.g., P204A, P204C).
Step 2: Inspect the reductant pressure sensor and its wiring/connector for damage, corrosion, or loose connections.
Step 3: Test the sensor signal voltage or frequency with a multimeter and compare to manufacturer specifications.
Step 4: Check DEF pump operation and pressure using a pressure gauge or scan tool data.
Step 5: Inspect DEF lines for blockages, kinks, or leaks.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to reduced engine performance, limp mode, and potential damage to the DEF system or emissions components. Additionally, it may cause the vehicle to fail emissions tests.
How much does it cost to fix?▼
The cost to fix P204B typically ranges from $150 to $400, depending on the cause. Replacing the reductant pressure sensor costs $50-$150 for parts and $100-$250 for labor. If the DEF pump or lines need repair, costs can be higher.