Reduction Agent Pressure Sensor Circuit Low
The reduction agent pressure sensor is reading a low voltage signal, indicating a possible fault.
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What it means (plain English)
The computer is getting a lower than expected voltage from the pressure sensor that measures how much DEF fluid is present. It should see around 0.5 to 5 volts under normal conditions.
What the computer is actually seeing
The engine control module (ECM) expects a pressure signal from the sensor, typically between 0.5V (low pressure) and 5V (high pressure). When it sees a voltage below 0.5V, it triggers this fault code.
What a healthy reading looks like
Expected voltage from the pressure sensor should be within the range of 0.5V to 5V when the system is operating under normal conditions.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check DEF fluid level in the tank. Ensure it is above the minimum level required by the system.
- 22. Inspect the wiring and connectors associated with the reduction agent pressure sensor for damage or corrosion.
- 33. Measure voltage at the reduction agent pressure sensor: It should be between 0.5V and 5V with the engine running. If voltage is below 0.5V, proceed to the next step.
- 44. Disconnect the sensor connector and check the resistance of the sensor; replace if it is out of specification (typically specified by the manufacturer).
- 55. If wiring and sensor are good, perform a scan for ECM issues or further diagnostics as outlined in the service manual.
Common causes
- Faulty reduction agent pressure sensor
- Wiring issues (short to ground, open circuit)
- Connector problems (corrosion or loose connection)
- Low DEF fluid level
- Defective ECM
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's not recommended to drive long with this fault; it could affect emissions and vehicle operation.
Will the code come back after clearing?
If the underlying issue is not resolved, the code will likely return.
Why does this code often appear with other codes?
It can indicate that the system is in a fail-safe mode, often due to other detected issues in the SCR system.
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