Diesel Exhaust Fluid Injector Stuck Closed
The P20DC code indicates that the powertrain control module (PCM) has detected that the exhaust aftertreatment fuel supply control valve is stuck in the closed position. This valve is part of the diesel exhaust fluid (DEF) injection system, which injects DEF into the exhaust stream to reduce NOx emissions. When stuck closed, DEF cannot be injected, leading to increased emissions and potential derate of engine power. This condition can be caused by a faulty valve, wiring issues, or a clogged DEF injector.
01. Most Common Causes
- Faulty exhaust aftertreatment fuel supply control valve
- Wiring or connector issues in the valve circuit
- Clogged or frozen DEF injector
- PCM software or hardware failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or derate
- Increased diesel exhaust fluid consumption
- Poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the DEF injector and supply valve for damage or contamination.
Step 3: Test the valve's electrical resistance and compare to specifications.
Step 4: Check wiring and connectors for shorts, opens, or corrosion.
Step 5: Perform a DEF injector flow test using a scan tool.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Driving with P20DC is not recommended as it can lead to reduced engine power and increased emissions. Continued operation may cause damage to the aftertreatment system.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, depending on the cause. Replacing the DEF injector or supply valve can cost $150-$400 for parts plus labor.