What Does P204D Mean?
The ECM has detected a voltage signal from the reductant pressure sensor that is above the normal operating range. This typically indicates an open circuit, short to voltage, or sensor internal failure.
Common Causes
40%
Faulty reductant pressure sensor with internal open circuit
25%
Open circuit in wiring harness or disconnected sensor connector
20%
Short to voltage in sensor signal wire
10%
Damaged or corroded sensor ground circuit
5%
ECM internal fault with pull-up resistor circuit
Diagnostic Steps
1
Step 1: Inspect sensor connector for looseness, backing out pins, or physical damage
2
Step 2: With key on engine off, backprobe sensor signal wire and verify voltage (should not be at battery voltage)
3
Step 3: Disconnect sensor and measure voltage at ECM side of harness (should show reference voltage 4.5-5V)
4
Step 4: Check sensor ground circuit continuity and resistance to chassis ground
5
Step 5: If all circuits test normal, replace reductant pressure sensor and clear codes
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
The ECM has detected a voltage signal from the reductant pressure sensor that is above the normal operating range. This typically indicates an open circuit, short to voltage, or sensor internal failure.
The most common cause of P204D (Reductant Pressure Sensor Circuit High) is: Faulty reductant pressure sensor with internal open circuit
Typical repair costs for P204D range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may limit engine power and display warning messages. Continued operation may result in vehicle derate or no-start condition after shutdown.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P204D to identify the root cause.
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Quick Info
Category
Powertrain
System
Selective Catalytic Reduction (SCR) Emissions System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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