P20E8: Reductant Pressure Too Low
8 vehicles · 8 makes · $150-$2,500 repair
Most Reported On
P20E8 is an OBD-II diagnostic trouble code meaning “Reductant Pressure Too Low.” P20E8 is a generic powertrain code that applies to diesel vehicles with a Selective Catalytic Reduction (SCR) emissions system, which injects diesel exhaust fluid (DEF, also sold as AdBlue) into the exhaust to convert smog-forming nitrogen oxides into harmless nitrogen and water. The engine control module sets this code when the DEF pump cannot build or hold the pressure the system needs (roughly 70-90 psi on most applications) to dose fluid accurately into the exhaust stream. Day to day you may notice little beyond a check engine light and a DEF or SCR warning message, though some vehicles show reduced power. Because SCR operation is emissions-mandated, ignoring the code typically starts a countdown to a derate: the vehicle will progressively limit speed (often to 55 mph, then as low as 5 mph on trucks) or refuse to restart until the fault is repaired. Some manufacturers word the same code as "DEF Pressure Too Low" or "SCR Urea Pressure Too Low," but the meaning is identical. This code is most commonly reported on 2011-2022 Volkswagen Touareg, 2016-2021 Volvo V60, and 2022-2025 Mazda CX-60 (3.3 Diesel, e-Skyactiv D), plus 5 other vehicles, with repair costs ranging from $150 to $2,500.
Common Causes
Typical Repair Cost
Based on 8 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P20E8, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
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Vehicles Affected (8)
FAQ
What does P20E8 mean?
P20E8 stands for "Reductant Pressure Too Low." P20E8 is a generic powertrain code that applies to diesel vehicles with a Selective Catalytic Reduction (SCR) emissions system, which injects diesel exhaust fluid (DEF, also sold as AdBlue) into the exhaust to convert smog-forming nitrogen oxides into harmless nitrogen and water. The engine control module sets this code when the DEF pump cannot build or hold the pressure the system needs (roughly 70-90 psi on most applications) to dose fluid accurately into the exhaust stream. Day to day you may notice little beyond a check engine light and a DEF or SCR warning message, though some vehicles show reduced power. Because SCR operation is emissions-mandated, ignoring the code typically starts a countdown to a derate: the vehicle will progressively limit speed (often to 55 mph, then as low as 5 mph on trucks) or refuse to restart until the fault is repaired. Some manufacturers word the same code as "DEF Pressure Too Low" or "SCR Urea Pressure Too Low," but the meaning is identical.
What are the most common causes of P20E8?
The most common causes of P20E8 are: Failed or weak DEF (reductant) pump that cannot build specified pressure, Clogged reductant pump filter cartridge — DEF crystals gumming the internal filter is the most common cause on Duramax and Power Stroke trucks, Contaminated, diluted, or crystallized DEF fluid (or DEF frozen in cold weather due to a failed heater), Leaking DEF supply lines or fittings, or a DEF injector stuck open and bleeding off pressure, Faulty reductant pressure sensor giving a false low reading, Damaged or corroded wiring/connectors to the DEF pump or pressure sensor, Low DEF tank level. The specific cause varies by vehicle.
How much does it cost to fix P20E8?
Repair costs for P20E8 range from $150 to $2,500, depending on the vehicle and root cause.
Which vehicles are affected by P20E8?
Au7o has documented P20E8 across 8 vehicle models from 8 manufacturers: Jeep, Mazda, Mercedes-Benz, Opel, Peugeot, Skoda, Volkswagen, Volvo.
Sources (12)
- ForumAdBlue Fault, no start countdown — Club Touareg Forum
- ForumAdBlue Sensor Malfunctions — Club Touareg Forum
- articleVolkswagen AdBlue/DPF/EGR System Failures and Solutions — Otoideal
- ForumAdBlue system problem - Volvo Owners Forum
- articleAdBlue system errors when the NOx sensor does not work - NOx Sensor Expert
- ForumCX-60 and AdBlue issue - Mazda CX-70 Forum
- ForumAdblue system fault | Skoda Kodiaq SUV Forum
- ForumSkoda Kodiaq 2.0 TDI problems with DPF regeneration | MyCarly Community
- articleDPF warning light ON in Skoda Kodiaq. What to check? | DailyDriven
- ForumAdblue tank replacing and updating the ECU to accept the new tank and electrical components | Peugeot 208 Forums (208ownersclub)
- articlePeugeot & Citroen AdBlue failure fix (lists 208; P20E8/P20EE, urea light, countdown) — Torx Tuning
- articlePeugeot AdBlue Fault Fixed (208 BlueHDi listed; P20E8, pump/PCB failure, non-start) — Fastlane Performance
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.