P20DA: Exhaust Aftertreatment Fuel Supply Control Circuit High

For the supply valve ahead of the exhaust doser, the control line reads too high, typically because it touches battery voltage or, on some drivers, an open line pulled up internally. Volvo and Mack log it as P20DA00 and list it in guide KC-2157 among the AHI module electrical faults, with the instruction to check that module's wiring and connector. A circuit stuck high leaves the valve unable to follow commands, so the control unit stops dosing and active regeneration is lost until the fault is repaired. Its siblings are P20D7 (line broken) and P20D9 (line grounded); a mechanically stuck valve sets P20DB or P20DC.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

Check engine light on
Active regeneration not possible

Most likely causes

Valve control wire shorted to a powered line
Damaged coil in the supply valve
Faulty output stage in the control module

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P20DA means

P: Powertrain: engine and transmission
2: Generic code: same on every make
0: Subsystem depends on the code range
DA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P20DA?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P20DA?

The most common causes are: valve control wire shorted to a powered line; damaged coil in the supply valve; faulty output stage in the control module.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.