Reductant Injection Air Pressure Too High
The P20E7 code indicates that the engine control module (ECM) has detected excessive air pressure in the reductant injection system, which is part of the Selective Catalytic Reduction (SCR) system. This system injects diesel exhaust fluid (DEF) into the exhaust stream to reduce NOx emissions. The air pressure is used to atomize the DEF; when it's too high, it can cause over-injection or improper mixing, leading to reduced SCR efficiency and potential emissions non-compliance. Common causes include a faulty reductant injection air pressure sensor, a stuck-open air pressure regulator, or a blocked air line.
1. Most Common Causes
- DEF system purge/vent valve blocked or restricted
- DEF injector (nozzle) clogged or stuck
- Reductant air pressure sensor faulty or out of calibration
- DEF system air supply line or hose kinked or collapsed
- DEF dosing pump defective (internal air mechanism stuck)
- Short circuit or high signal in air pressure sensor wiring
- PCM/DCM control module damaged (uncommon)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power loss
- Increased exhaust emissions
- Possible DEF system warnings on dashboard
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 injection air pressure sensor and wiring for damage or corrosion.
Step 3: Check the air pressure regulator and air lines for blockages or leaks.
Step 4: Monitor live data for air pressure readings and compare to manufacturer specifications.
Step 5: If necessary, perform a reductant injection system test to verify operation.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can lead to reduced engine performance, increased emissions, and potential damage to the SCR system. Immediate diagnosis and repair are advised.
How much does it cost to fix?▼
The cost to fix P20E7 typically ranges from $150 to $400, depending on the root cause. Sensor replacement may cost $150-$250, while regulator or line repairs can be $200-$400.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.