P20E8: Reductant Pressure Too Low
The DEF pump isn't building enough pressure to dose.
Green, yellow, red: three ways P20E8 can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Set once in freezing weather, cleared after warm-up.
Schedule a repair
Returns. Get the DEF pump and lines checked.
Stop and get help
Countdown or derate. Stop and get help.
Symptoms you might notice
- DEF warning
- Countdown
Common causes, cheapest first
- Low DEF
- Clogged DEF filter or lines
- Crystallized DEF
- Weak DEF pump
- Frozen DEF
What you can check before calling
- Check DEF level
- Look for crystals at lines and doser
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Want the full story? Read our guide: DEF warning lights and derate: what diesel drivers need to know.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
Related codes
More diesel & cummins codes
- P2002
Diesel Particulate Filter Efficiency Below Threshold (Bank 1) - P2463
Diesel Particulate Filter Restriction - Soot Accumulation - P242F
Diesel Particulate Filter Restriction - Ash Accumulation - P2459
Diesel Particulate Filter Regeneration Frequency - P2453
Diesel Particulate Filter Pressure Sensor A Circuit Range/Performance - P2454
Diesel Particulate Filter Pressure Sensor A Circuit Low
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does P20E8 mean?
P20E8 means "Reductant Pressure Too Low". The DEF pump isn't building enough pressure to dose.
Can I drive with code P20E8?
It depends on what the vehicle is doing. Green: Set once in freezing weather, cleared after warm-up. Yellow: Returns. Get the DEF pump and lines checked. Red: Countdown or derate. Stop and get help.
What causes P20E8?
The most common causes are: low DEF; clogged DEF filter or lines; crystallized DEF.
Is P20E8 a serious code?
It can be. Countdown or derate. Stop and get help.
Skip the shop. We'll come to you.
Book online in about a minute, or call or text the office. We'll confirm the details and get a mechanic headed your way.