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

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.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Compare the reading with other engine data while varying the engine speed.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P20EA means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 0: Subsystem depends on the code range
• EA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P20EA?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P20EA?

The most common causes are: 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.

Related codes

• P20EBReductant Control Module Power Relay De-Energized Performance - Too Late
• P068AECM/PCM Power Relay De-Energized Performance Too Early
• P068BECM/PCM Power Relay De-Energized Performance Too Late
• P21C7Reductant Control Module Power Relay/Relays Control Circuit/Open
• P056DReductant Control Module System Voltage

Sources

• fordservicecontent.com: obd summary diesel 2023
• saabwisonline.com: dtc p068a or p068b
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.