Reductant Pressure Too Low
The pressure in the DEF system is below the expected level.
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What it means (plain English)
This code means there isn’t enough pressure in the Diesel Exhaust Fluid (DEF) system to properly inject the fluid into the exhaust and reduce emissions.
What the computer is actually seeing
The Engine Control Module (ECM) monitors the DEF pressure using a pressure sensor. It expects a pressure reading between 5-12 PSI during operation. A reading below 5 PSI triggers this fault.
What a healthy reading looks like
Normal DEF pressure should be between 5-12 PSI.
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 the DEF tank level. Is it below the minimum required? If yes, refill and clear the code. If no, proceed to step 2.
- 22. Inspect all DEF lines and connections for leaks or damage. Are there visible issues? If yes, repair or replace as needed. If no, go to step 3.
- 33. Check the DEF pressure sensor's electrical connections. Are the connectors secure and free of corrosion? If no, repair as necessary. If yes, proceed to step 4.
- 44. Using a scan tool, monitor the DEF pressure sensor data while starting the engine. Is the reading between 5-12 PSI? If no, replace the DEF pressure sensor. If yes, go to step 5.
- 55. Inspect the DEF injection system components. Do they operate correctly? If no, repair or replace as needed. If yes, clear the code and test drive the vehicle.
Common causes
- Low DEF level in the tank
- Clogged DEF lines or filter
- Faulty DEF pressure sensor
- Leaking DEF lines or connections
- Defective DEF injection system components
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I drive with this code active?
It's not recommended to drive long distances as it affects emissions control, but you may be able to drive short distances with reduced engine performance.
Will this code come back after repairs?
If the root cause is properly addressed, the code should not return.
Why do I see this code with low DEF fluid?
Low DEF fluid can cause insufficient pressure, triggering this code as the system cannot inject the proper amount for emissions reduction.
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