P20E9 — Reductant Pressure Too High — 6.7 Cummins (SCR / DEF)

Diagnostic reference for P20E9 on 6.7L Cummins SCR/DEF 2013–present.

Updated October 15, 2026

What it means

Generic definition: DEF (reductant) line pressure is higher than expected. On the 6.7L Cummins this is a DEF/SCR reductant pressure fault, not a fuel-rail pressure code. Typical on this platform: check for a restricted or crystallised DEF doser or line, and the DEF pump and pressure sensor.¹

Most likely causes

1. Restricted or crystallised DEF doser / dosing line causing back-pressure — DEF crystallisation or debris can block the doser or line, raising reductant line pressure. Inspect doser and line for restriction/crystallisation.¹
2. DEF supply module / pump fault causing over-pressure — Pump or internal pressure regulation fault can drive reductant pressure above target. Evaluate pump operation and pressure control.¹
3. DEF pressure sensor reading high / sensor fault — Erroneous high reading from the reductant pressure sensor can set the code. Verify sensor signal vs actual pressure.¹

How to diagnose

1. Verify code and freeze-frame; confirm P20E9 is present on 6.7L Cummins SCR/DEF and not a fuel-rail pressure issue.
2. Inspect DEF tank, lines, doser and injector for visible crystallisation, blockage or kinks that could raise back-pressure.
3. Check DEF quality and for contamination/freezing that could restrict flow.
4. Assess DEF supply module/pump operation and pressure regulation behavior using scan tool data (do not perform high-pressure fuel injection service).
5. Compare reductant pressure sensor reading to expected values and check wiring/connectors for faults.
6. Review recent DEF service history and any recent dosing-system work for introduced restrictions.
7. If conditions allow, clear code and monitor reductant pressure during a controlled drive cycle to confirm repeatability.

Specs and test values

Common mistake to avoid

Adding just a little DEF to clear the 5 mph warning. Ram’s bulletin says at least 2.5 gallons must go in before the system resets the message. Source: Ram service bulletin 25-005-14 (Diesel Exhaust Fluid).

Parts and tools you may need

• Scan tool with Cummins/SCR live data
• DEF-safe PPE and container
• Inspection light and borescope
• Multimeter
• Wiring diagram for DEF supply module and pressure sensor

Tools you’ll need

• OBD-II scan tool — Reads P20E9 and live DEF reductant pressure data to confirm high pressure and monitor behavior during a drive cycle.
• Digital multimeter — Checks DEF pressure sensor supply, ground, and signal voltage to rule out wiring or sensor faults.
• Borescope — Inspects DEF doser, dosing line, and injector for crystallization or blockage without disassembly.
• DEF refractometer — Verifies DEF concentration/quality to identify contamination or dilution that can cause crystallization and back-pressure.

Rough cost and difficulty

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

High-pressure reductant and emissions systems require calibrated tools and safety procedures. If you are not trained on SCR/DEF diagnostics, have a qualified diesel technician perform testing and repairs.

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: P20E9 on the 6.7 Cummins '13+

Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.

P20E9 P2BAC HOW TO REPLACE DEF PUMP ON RAM TRUCK - It finally went out! — 4M Ranch · 79K views