P20E8 on Volvo
Reductant Pressure Too Low
P20E8 on Volvo vehicles indicates reductant pressure too low. Au7o has documented this code across 1 Volvo model — most commonly on V60. 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. Typical repair costs on Volvo range from $300 to $1,200, depending on the specific model and root cause.
Common Causes of P20E8
- •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
P20E8 on Volvo by Model
Volvo V60(1 issue)
- AdBlue / SCR NOx Sensor Faults and Start-Prevented Countdown2016-2021
On AdBlue/SCR-equipped diesel V60s, faults in the NOx sensors and AdBlue dosing system are common. A drifting or failed NOx sensor makes the system believe the SCR catalyst is not reducing emissions, throwing AdBlue/dosing warnings and limp mode. Critically, persistent NOx/SCR faults trigger an emissions 'start-prevented' countdown that, if ignored, will refuse to restart the engine. Air trapped in the dosing line, a faulty dosing valve/module, or contaminated AdBlue can produce the same symptoms.
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View P20E8 across all makes →Frequently Asked Questions
What does P20E8 mean on Volvo?▼
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. On Volvo specifically, this code is documented across 1 model.
What causes P20E8 on Volvo vehicles?▼
Common causes on Volvo: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P20E8 on a Volvo?▼
Repair costs on Volvo range from $300 to $1,200, depending on the specific model and root cause.
Which Volvo models have P20E8 documented?▼
Au7o has documented P20E8 on 1 Volvo model: V60.