What it means
This code indicates a high voltage condition in the exhaust aftertreatment fuel supply control circuit.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The aftertreatment fuel supply control circuit operates fuel delivery for hydrocarbon dosing during DPF regeneration. The module monitors the circuit's electrical level and sets P20DA when it detects a voltage higher than expected, which can indicate a short to battery voltage or a wiring or connector fault.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light on
- DPF regeneration may be delayed or incomplete
- Reduced engine power in some vehicles
How to diagnose it
- Review freeze-frame data and scan-tool fault status to establish when the high-circuit reading occurred and whether it is still present.
- Inspect the control-circuit harness for pinching against a power source, damaged insulation, water intrusion, corrosion, or displaced connector pins.
- Check live circuit data while gently moving the harness near the aftertreatment fuel supply control component to look for a changing signal.
- Test the circuit for a short to battery voltage and check connector voltage drops using the manufacturer's procedure.
- If the circuit wiring is intact, verify the control component and module driver operation against the manufacturer's specification.
Common fixes
- Secure a loose connector and clean corroded control-circuit terminals.
- Repair wiring pinched against a power feed or with damaged insulation.
- Replace damaged connector terminals or seals that allow water intrusion.
- Replace a failed control component only after confirming the circuit is not shorted to voltage.
Can I keep driving?
If the engine runs normally, limit driving to necessary trips and avoid heavy loads because DPF regeneration may not work as intended. Have it checked promptly if power falls or the fault returns immediately.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.