Powertrain, generic (extended)

P20A3 Reductant Purge Control Valve A Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P20A3 is the high-side fault of the purge valve circuit: the line carries voltage or current where it should not. GM detects it on the 6.6 L Duramax while the low-side driver is switched on; an impedance of less than 0.5 Ω to controller power lasting 3 s triggers it as a Type A fault. Volkswagen's test for the 2014 Touareg V6 TDI (engine CNRB) looks at current instead and reports P20A3 above 3.00 A, which indicates a short across the coil or to battery positive. A driver that sees such overcurrent switches off to protect itself, so the valve no longer reverses the pump, and the line is not emptied at shutdown. P20A2 covers the opposite short to ground and P20A0 the open circuit. Look for a shorted coil, a wire touching a supply cable or a damaged connector at the supply module.

Likely causes

Valve coil with shorted windings drawing excessive current
Control wire shorted to a battery-fed conductor
Damaged or DEF-contaminated connector bridging pins

Symptoms

  • MIL on in the first trip (GM Type A)
  • DEF warning and possibly further pump codes
  • In frost, risk of DEF freezing in the line

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

P20A0P20A2P20A1P24DE

References: gsi.ext.gm.com, static.nhtsa.gov, law.cornell.edu.