Exhaust Aftertreatment Fuel Supply Control Circuit Low
The P20D9 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the exhaust aftertreatment fuel supply control circuit. This circuit controls the delivery of fuel to the aftertreatment system for regeneration of the diesel particulate filter (DPF) or selective catalytic reduction (SCR) system. A low voltage reading suggests a short to ground, open circuit, or faulty component in the fuel supply control circuit, which can prevent proper regeneration and lead to increased emissions and potential DPF clogging.
01. Most Common Causes
- Faulty exhaust aftertreatment fuel supply control module
- Short to ground in the control circuit wiring
- Open circuit or poor connection in the fuel supply control circuit
- Failed fuel injector or fuel pump for aftertreatment system
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced fuel economy
- Increased exhaust emissions
- Possible DPF regeneration issues or warning lights
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the wiring and connectors related to the aftertreatment fuel supply control circuit for damage, corrosion, or loose connections.
Step 3: Test the circuit voltage and resistance with a multimeter to identify shorts or opens.
Step 4: Check the fuel supply control module and related components for proper operation; replace if faulty.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code as it can lead to DPF clogging and more expensive repairs. Short trips may be okay, but have it diagnosed promptly.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary; if it's a simple wiring fix, it may be under $200, but replacing a control module or injector can cost $500-$1500.