Reductant Control Module Power Relay De-Energized Too Early
The P20EA code indicates that the reductant control module (RCM) power relay has de-energized earlier than expected. This relay supplies power to the RCM, which manages the diesel exhaust fluid (DEF) system. When the relay opens prematurely, the RCM loses power, disrupting DEF injection and potentially causing increased NOx emissions. Common causes include a faulty relay, wiring issues, or a failing RCM.
1. Most Common Causes
- Faulty reductant control module power relay
- Corroded or damaged relay socket/connector
- Open or short circuit in relay control wiring
- Failing reductant control module
2. Symptoms You Will Notice
- Check Engine Light on
- Reduced engine power or limp mode
- Increased diesel exhaust fluid consumption
- Possible failed emissions test
3. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P20EA is present.
Step 2: Inspect the RCM power relay and its socket for corrosion or damage.
Step 3: Test relay coil resistance and switching operation with a multimeter.
Step 4: Check for battery voltage at relay input and output terminals with key on.
Step 5: Inspect wiring and connectors between relay, RCM, and PCM for shorts or opens.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can lead to reduced engine performance and increased emissions. Limp mode may activate, limiting speed.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for a relay replacement, but could be higher if wiring repairs or module replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.