Reductant Injection Air Pressure Too Low
The P20E6 code indicates that the engine control module (ECM) has detected that the air pressure supplied to the reductant injector (used in diesel exhaust fluid systems) is below the required threshold. This typically occurs in diesel vehicles equipped with Selective Catalytic Reduction (SCR) systems. The reductant injection system uses compressed air to atomize and inject diesel exhaust fluid (DEF) into the exhaust stream. Low air pressure can result from a faulty air pump, clogged air lines, leaks, or a defective pressure sensor. This condition can lead to insufficient DEF injection, causing increased NOx emissions and potential damage to the SCR system.
01. Most Common Causes
- Faulty reductant injection air pump
- Clogged or restricted air lines
- Leaking air hoses or connections
- Defective air pressure sensor
- Faulty reductant injector
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance
- Increased exhaust emissions
- Possible DEF warning light
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Inspect the air pump and listen for operation; check for proper voltage and ground.
Step 3: Visually inspect air lines for cracks, kinks, or disconnections.
Step 4: Test air pressure at the injector using a pressure gauge; compare to manufacturer specs.
Step 5: Check the air pressure sensor and wiring for damage or corrosion.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can lead to increased emissions and potential damage to the SCR system. The vehicle may enter limp mode to protect the engine.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on the root cause. Replacing an air pump can cost $200-$350, while sensor replacement may be $100-$200.