Powertrain, generic (extended)

P20EA Reductant Control Module Power Relay De-Energized Performance - Too Early

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Many SCR systems supply the reductant control module, and through it pump and heaters, via a power relay. After the key is switched off the relay should stay energised for a short after-run so the pump can empty the lines and the module can save its learned values, and only then drop out on the module's command. P20EA means the supply disappeared before that point. Fluid left in the lines can then freeze or crystallise, and stored data may be lost. No maker documents P20EA publicly. The monitoring follows the engine-module pair P068A/P068B: Saab's 2011 9-5 diesel reads back the relay voltage on its control line, and Ford's 2023 diesel summary checks the reductant control module relay (P21C7) by comparing commanded state with the measured voltage. A relay that drops out late is P20EB.

Likely causes

Worn relay contacts or coil interrupting the supply early
Loose fuse, terminal or ground in the relay or module feed
Battery disconnected or voltage collapsing right after shut-off
Reductant control module releasing the relay prematurely

Symptoms

  • Check engine light, often without noticeable driving symptoms
  • DEF lines not purged, risk of frozen or crystallised lines in winter

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

P20EBP068AP068BP21C7P056D

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