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) system. A delayed de-energization can cause the module to remain powered when it shouldn't, potentially draining the battery or causing communication issues. This code is often triggered by a faulty relay, wiring problems, or a failing reductant control module.
1. Most Common Causes
- Faulty reductant control module power relay
- Corroded or damaged relay socket or wiring
- Short circuit or open circuit in the relay control circuit
- Failing reductant control module
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Possible DEF system malfunction or reduced performance
- Battery drain if relay stays energized
- No start or hard start in some cases
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Inspect the reductant control module power relay and its socket for corrosion, damage, or loose connections.
Step 3: Test the relay for proper operation using a multimeter (check coil resistance and switching function).
Step 4: Check for battery voltage at the relay control circuit with the key on and off to identify shorts or opens.
Step 5: If relay and wiring are good, test the reductant control module for internal faults.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive with this code as it may cause battery drain or DEF system issues, potentially leading to reduced engine performance or a no-start condition.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the relay, wiring, or module needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.