Powertrain, generic (extended)

P20EB Reductant Control Module Power Relay De-Energized Performance - Too Late

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Here the opposite of P20EA happens: after the reductant control module has finished its after-run and released the power relay, voltage is still present on the switched side, so the relay opens late or not at all. Typical reasons are welded contacts, a control line shorted to ground that keeps the coil energised, or a module that never ends its shut-down. The DEF module, pump and heaters may then stay powered with the engine off, which drains the battery and keeps the system awake. No maker documents P20EB publicly. The check mirrors P068B on the engine module, which Saab's 2011 9-5 diesel derives from the relay control circuit, and Ford's 2023 diesel summary flags a reductant relay voltage above 0 V while the output stage is off (P21C7). CARB requires such SCR components to be monitored.

Likely causes

Welded or sticking relay contacts
Relay control line shorted to ground, keeping the coil energised
Reductant control module or network activity preventing shut-down

Symptoms

  • Check engine light
  • Battery drained after the vehicle has been parked
  • DEF pump or relay audible long after switching off

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–600
Time0.3–2 h

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

Parts involved

reductant control modulereductant supply relay

Related codes

P20EAP068BP068AP21C7P056D

References: saabwisonline.com, fordservicecontent.com, law.cornell.edu.