Low or empty diesel exhaust fluid (DEF) tank, or DEF that has frozen or degraded; Weak or failing reductant pump unable to build sufficient pressure; Clogged or restricted reductant filter or strainer; Leak in the reductant lines, injector, or pressure sensor fittings; Faulty reductant pressure sensor providing an inaccurate low reading; Kinked, pinched, or blocked reductant line preventing proper flow; Electrical issues such as damaged wiring or corroded connectors to the pump or sensor

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20E1

P20E1Reductant Pressure Too Low

Q: What does code P20E1 mean?

Reductant Pressure Too Low. P20E1 indicates that the reductant pressure in the selective catalytic reduction (SCR) system is lower than the powertrain control module expects during operation. The computer monitors the pressure sensor in the reductant injection system and sets this code when the measured pressure falls below the commanded value for a calibrated time, often due to a weak pump, a leak, or a restriction.

P20E1 indicates that the reductant pressure in the selective catalytic reduction (SCR) system is lower than the powertrain control module expects during operation. The computer monitors the pressure sensor in the reductant injection system and sets this code when the measured pressure falls below the commanded value for a calibrated time, often due to a weak pump, a leak, or a restriction.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode triggered by the powertrain control module
A message on the dashboard indicating low reductant pressure or a fault in the emissions system
Rough running or hesitation if the system enters a protective strategy
Increased diesel exhaust fluid (DEF) consumption in some cases due to the system trying to compensate

Common causes, most likely first

Low or empty diesel exhaust fluid (DEF) tank, or DEF that has frozen or degraded
Weak or failing reductant pump unable to build sufficient pressure
Clogged or restricted reductant filter or strainer
Leak in the reductant lines, injector, or pressure sensor fittings
Faulty reductant pressure sensor providing an inaccurate low reading
Kinked, pinched, or blocked reductant line preventing proper flow
Electrical issues such as damaged wiring or corroded connectors to the pump or sensor

How to diagnose and fix it

Check the DEF tank level and top off with the correct specification fluid if low
Inspect the reductant system for visible leaks, kinks, or damage to lines and fittings
Test the reductant pressure sensor and its wiring for proper signal and continuity
Replace the reductant filter or strainer if restricted, following the manufacturer's interval
Perform a commanded pump activation test with a scan tool to verify pump operation and pressure build-up
Replace the reductant pump if it fails to generate the specified pressure under command
Clear the code and perform a road test or drive cycle to confirm the repair and ensure the code does not return

Before you replace the reductant pump

A low DEF level or degraded fluid is a common cause that is often overlooked because the system may not set a separate low-level code first.
The pressure sensor can fail in a way that reports low pressure even when the pump is working correctly, leading to unnecessary pump replacement.
Air pockets or air ingestion in the reductant lines after a refill or repair can cause temporary low-pressure codes that clear after proper priming.
Extreme cold weather can cause DEF to freeze and temporarily block flow, setting a low-pressure code that may resolve once the vehicle warms up.
A restricted DEF filter may not trigger a separate code but can cause low pressure at the injector, mimicking a failing pump.

Can I keep driving with P20E1?

It is generally safe to drive with P20E1 set, but the vehicle may enter limp mode or limit speed, so avoid long trips and heavy loads until the fault is repaired. Continued driving with low reductant pressure can lead to more extensive emissions system damage and increased repair costs.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.