Exhaust Aftertreatment Fuel Supply Control Performance
The P20D8 code indicates a performance issue with the exhaust aftertreatment fuel supply control system, typically found in diesel engines. This system injects fuel into the exhaust stream to regenerate the diesel particulate filter (DPF) or to heat the selective catalytic reduction (SCR) system. The powertrain control module (PCM) has detected that the actual fuel flow or pressure does not match the commanded value, often due to a faulty fuel injector, pump, or wiring issue.
01. Most Common Causes
- Faulty exhaust aftertreatment fuel injector
- Clogged or leaking fuel supply lines
- Defective fuel pump or pressure sensor
- Wiring or connector issues in the fuel supply control circuit
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased exhaust emissions
- Possible DPF regeneration issues or frequent regeneration cycles
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data to understand conditions when code set.
Step 2: Visually inspect fuel supply lines, injector, and connectors for damage, leaks, or corrosion.
Step 3: Use a scan tool to command the aftertreatment fuel injector and monitor fuel pressure or flow to verify operation.
Step 4: Test the fuel injector resistance and actuation with a multimeter or oscilloscope.
Step 5: Check the fuel pump and pressure sensor signals for proper voltage and ground.
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 incomplete DPF regeneration, increased emissions, and potential damage to the exhaust aftertreatment system. Short trips may be possible but should be minimized.
How much does it cost to fix?▼
The cost typically ranges from $150 to $500 depending on the root cause. Replacing a fuel injector or pump can be on the higher end, while repairing wiring or cleaning lines is less expensive.