P20E8 — Reductant Pressure Too Low — 6.7 Powerstroke
P20E8 on 6.7 Powerstroke means the DEF (reductant) delivery pressure is below target. The PCM monitors SCR/DEF pressure and sets the code when measured…
What it means
DEF (reductant) delivery pressure is below target.1
Most likely causes
- DEF pump performance / failure — The DEF pump is the primary source of reductant pressure for the SCR system. Low or erratic pump output will set P20E8.1
- Frozen or clogged DEF line / filter — Ice formation in cold weather or crystallized DEF can block flow and cause low reductant pressure.1
- Dosing valve / injector restriction — A restricted or sticking dosing valve reduces system pressure seen by the PCM.1
How to diagnose
- Verify freeze conditions and DEF quality; confirm recent DEF service history.
- Check live reductant pressure PID vs. commanded pressure at idle and during a DEF pump prime event.
- Inspect DEF tank, pump module, lines, and filter for ice, crystallization, kinks, or contamination.
- Check electrical power and ground to the DEF pump and monitor pump command % and actual pressure response.
- Review freeze-frame and related SCR codes (e.g., reductant system performance) for supporting clues.
- If pressure remains low with good electrical supply, suspect pump performance or a hydraulic restriction in the DEF delivery circuit.
Specs and test values
| Check | Normal reading | When to measure | Source |
|---|---|---|---|
| DEF urea concentration | 32.5% (check with a DEF refractometer) | Sample from the tank | Ram service bulletin 25-005-14 (Diesel Exhaust Fluid) |
| DEF freeze point | About 12°F (−11°C); freezing alone is normal and the system is built to thaw it | Cold weather | Ram service bulletin 25-005-14 (Diesel Exhaust Fluid) |
Common mistake to avoid
Replacing sensors, the doser or the SCR catalyst before testing the DEF. Old, heat-stored or diluted DEF loses strength and sets the same efficiency codes. Check it with a refractometer first. Source: Ram service bulletin 25-005-14 (Diesel Exhaust Fluid).
Parts and tools you may need
- Scan tool with live SCR/DEF PIDs
- Multimeter
- DEF-compatible container and approved DEF
- Basic hand tools for inspection
Tools you’ll need
- OBD-II scan tool — Reads reductant pressure PIDs and pump command % to compare actual vs. commanded pressure during prime and idle.
- digital multimeter — Verifies battery voltage and ground at the DEF pump connector and checks pump command circuit integrity.
- fuel pressure gauge — Confirms low DEF hydraulic pressure at the pump outlet or dosing valve inlet when electricals are good.
- inspection mirror — Lets you see DEF lines, filter, and tank module for ice, crystallization, kinks, or contamination without full disassembly.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| DEF system drain, flush and refill (contaminated fluid) | $50–$200 | 1–3 hrs | DIY with tools and a manual |
| DEF injector (doser) | $200–$600 | 0.5–2 hrs | DIY with tools and a manual |
| DEF pump / supply module | $400–$1,200 | 1–3 hrs | DIY with tools and a manual |
Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.
When to see a pro
If pressure does not recover after confirming DEF quality and clearing ice/contamination, have a qualified diesel technician test the DEF pump and dosing circuit. Do not attempt high-pressure fuel system service. This guide is diagnostic only. Sources are for reference; always follow OEM service information.
Check for recalls
Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.
Sources
Repair videos: P20E8 on the 6.7 Power Stroke
Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.
Spotted an error, or something missing? Tell us
Run a 6.7 Powerstroke? This goes straight to the editor — it is not published.