Faulty fuel quantity actuator Y231 (internal solenoid failure or worn valve); Damaged or corroded electrical connector at the actuator; Open or short circuit in the wiring harness between the ECM and the actuator; Contaminated or degraded diesel fuel causing actuator sticking; ECM software fault or internal driver circuit failure (less common); Low fuel pressure or air intrusion in the fuel system affecting actuator operation

DTC codes / Mercedes-Benz codes / P1220

P1220 · Mercedes-BenzFuel Quantity Actuator Y231

Q: What does code P1220 mean?

Fuel Quantity Actuator Y231. P1220 on Mercedes-Benz vehicles indicates that the engine control module (ECM) has detected an implausible signal or a fault within the circuit for the fuel quantity actuator Y231, which is the solenoid valve that meters fuel delivery on the high-pressure injection pump. The ECM monitors the actuator's electrical current and expected position, and when the feedback does not match commanded values, it stores this code and typically illuminates the check engine light.

P1220 on Mercedes-Benz vehicles indicates that the engine control module (ECM) has detected an implausible signal or a fault within the circuit for the fuel quantity actuator Y231, which is the solenoid valve that meters fuel delivery on the high-pressure injection pump. The ECM monitors the actuator's electrical current and expected position, and when the feedback does not match commanded values, it stores this code and typically illuminates the check engine light.

SystemPowertrain

Code typeMercedes-Benz specific

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine power or limp-home mode due to the ECM limiting fuel quantity
Rough idle, hesitation, or stumbling during acceleration
Difficulty starting or extended cranking, especially when cold
Increased fuel consumption or black smoke from the exhaust
In rare cases, the engine may stall or fail to start altogether

Common causes, most likely first

Faulty fuel quantity actuator Y231 (internal solenoid failure or worn valve)
Damaged or corroded electrical connector at the actuator
Open or short circuit in the wiring harness between the ECM and the actuator
Contaminated or degraded diesel fuel causing actuator sticking
ECM software fault or internal driver circuit failure (less common)
Low fuel pressure or air intrusion in the fuel system affecting actuator operation

How to diagnose and fix it

Perform a visual inspection of the actuator connector and wiring for damage, corrosion, or loose pins
Check the actuator's electrical resistance and compare to Mercedes-Benz specifications
Measure voltage and current at the actuator connector while cranking or running to verify signal integrity
Inspect the fuel system for contamination, water, or air leaks that could affect actuator performance
If electrical checks pass, remove and inspect the actuator for mechanical sticking or debris
Replace the fuel quantity actuator Y231 if faulty, then clear the code and perform adaptation reset
If the fault persists, diagnose the ECM and its software, updating or replacing as needed

Before replacing the fuel quantity actuator

A common misdiagnosis is replacing the actuator when the real problem is a chafed wire in the harness near the engine mount, which can short intermittently with engine vibration.
Contaminated diesel fuel or water in the fuel system can cause the actuator to stick, setting P1220 without any electrical fault; always check fuel quality before condemning the actuator.
On some Mercedes-Benz models, a weak battery or poor ground connection can cause voltage spikes that mimic actuator failure, so verify battery and ground integrity first.
The ECM may set P1220 as a result of a failed adaptation after a fuel system repair; performing a reset and relearn procedure can clear the code without parts replacement.
A stuck-open EGR valve or intake leak can alter air-fuel ratios and cause the ECM to command unusual fuel quantities, indirectly triggering P1220; check for related codes.

Can I keep driving with P1220?

You can usually drive the vehicle to a workshop, but avoid heavy acceleration or towing, as the engine may enter limp mode and lack power. If the engine stalls or runs very poorly, stop driving and seek professional diagnosis to prevent damage to the injection system.

Tools that help

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Guidance is general and written for Mercedes-Benz vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.