P20D9: Exhaust Aftertreatment Fuel Supply Control Circuit Low — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
The exhaust-aftertreatment fuel-supply control circuit has a low electrical signal condition. This is a circuit-level indication, not evidence that fuel pressure or delivered fuel quantity is physically low.
Affected system: Powertrain
Symptoms
- Warning light may illuminate
- Related system function may be impaired
- Vehicle-specific symptoms vary
Possible causes
- Fuel supply or pressure issue, restricted injector, actuator fault, connector or wiring damage
- Related wiring, connector, power or ground fault
- Vehicle-specific mechanical or control issue
What to check
- Record stored and pending codes and freeze-frame data
- Check fuel supply and pressure readings, electrical supply and ground, and the relevant injector or regulator circuit before replacing parts.
- Confirm measured values against the vehicle service information
- Retest under the conditions that set the code
- Check fuel supply and pressure readings, electrical supply and ground, and the relevant injector or regulator circuit before replacing parts.
- Repair the verified cause and confirm the code does not return
Also written as: P20D9-00, P20D900 (some scan tools add the fault-type byte, e.g. -00).