Reductant Control Module Power Relay De-Energized Performance - Too Late
The P20EB code indicates that the powertrain control module (PCM) detected that the reductant control module power relay de-energized later than expected. This relay supplies power to the reductant control module, which manages the diesel exhaust fluid (DEF) injection system. A delayed de-energization can cause the reductant control module to remain powered when it should be off, potentially draining the battery or causing communication issues. This code is typically set when the relay's switching time exceeds a calibrated threshold.
01. Most Common Causes
- Faulty reductant control module power relay
- Corroded or loose relay socket connections
- Wiring issues (shorts, opens, or high resistance) in the relay control circuit
- Faulty PCM or software glitch
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Possible battery drain if relay sticks closed
- Reduced fuel economy or performance issues
- DEF system malfunction or warning messages
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes (e.g., P20EE, P20EF).
Step 2: Inspect the reductant control module power relay and its socket for corrosion, damage, or loose pins.
Step 3: Test relay operation: measure voltage at the relay control circuit and check for proper switching using a multimeter.
Step 4: Check wiring and connectors between the relay, PCM, and reductant control module for continuity and shorts.
Step 5: If all else is fine, replace the relay and clear the code; if code returns, suspect PCM issue.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but the underlying issue may cause battery drain or DEF system failure, leading to reduced performance or limp mode. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (relay) and labor. If wiring or PCM replacement is needed, costs can be higher.