Reductant Pressure Too Low
The P20E8 code indicates that the diesel exhaust fluid (DEF) system has detected insufficient pressure in the reductant delivery system. This typically occurs when the DEF pump cannot maintain the required pressure to inject DEF into the exhaust stream for NOx reduction. Common causes include a faulty DEF pump, clogged injector, frozen DEF, or a leak in the supply lines. Low DEF pressure can lead to increased NOx emissions and may trigger a derate or limp mode to protect the aftertreatment system.
1. Most Common Causes
- Faulty DEF pump
- Clogged or frozen DEF injector
- Leaking DEF supply lines or connections
- DEF quality issues or contamination
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or derate mode
- Increased exhaust emissions
- Possible DEF warning messages on dashboard
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect DEF level and quality; ensure DEF is not frozen.
Step 3: Visually inspect DEF lines, pump, and injector for leaks or damage.
Step 4: Test DEF pump pressure using a scan tool or pressure gauge.
Step 5: Check DEF injector for clogs; clean or replace if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the vehicle may enter derate mode, reducing power and potentially causing further damage to the aftertreatment system.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: a DEF pump replacement can be $300-$800, while injector cleaning or replacement may be $100-$400.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.