Powertrain, generic (extended)

P20A0 Reductant Purge Control Valve A Circuit/Open

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

After the engine stops, many airless DEF systems suck the fluid out of the line and injector back into the tank so that nothing freezes there. In Bosch's Denoxtronic 2.2 this is done by a 4/2-way valve in the supply module that reverses the flow. P20A0 concerns the drive circuit of this valve, chiefly an interruption. GM checks it on the 6.6 L Duramax (LML/LGH) with the driver switched off: an impedance above 200 kΩ between ECM pin and load for 3 s sets the code, Type A. Volkswagen, on the 2014 Touareg 3.0 TDI (CNRB), uses a power-stage voltage between 2.97 and 4.70 V. Shorts to ground and to power are split off as P20A2 and P20A3. If the line cannot be emptied, DEF may stay in the injector and line and freeze there in winter.

Likely causes

Coil of the purge or reversing valve open

Connector at the supply module loose or corroded by DEF

Wire to the valve broken

Output stage in the engine or dosing control unit defective

Symptoms

MIL on (GM Type A, first trip)
DEF system or emission service message
Risk of frozen DEF line or injector in winter

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€50–1,500

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant purge valve

Related codes

P20A1 P20A2 P20A3 P20A5 P208A

References: gsi.ext.gm.com, static.nhtsa.gov, picoauto.com.