P0272

What P0272 Means

Code P0272 indicates a cylinder 4 contribution/balance fault. The DME (engine control unit) detects that cylinder 4 is producing less power than the others. This can be caused by a faulty fuel injector, mechanical problems (low compression, worn piston rings or valvetrain), or electrical faults (open or short in the injector circuit, poor contact).

The fuel injection and ignition systems run under DME control, which balances cylinder operation based on sensor signals. When cylinder 4 parameters deviate, the DME sets P0272 and may enter reduced-power mode to protect the engine.

Symptoms

• Misfires, especially noticeable at idle or under load.
• Rough idle / one-cylinder misfire (lumpy running), vibrations.
• Power loss, slower acceleration.
• Check Engine light on the instrument cluster.
• Possible jerking or hesitation while driving and worse fuel economy.

Diagnosis and Repair

1. Read fault codes with diagnostic equipment (ISTA, INPA) and check for related misfire codes (e.g., P0304).
2. Check the cylinder 4 injector electrical circuit: wiring integrity, connectors, injector coil resistance. Replace the injector if needed.
3. Check compression in cylinder 4. Low compression points to mechanical problems (worn rings, valves, burned piston).
4. Check the ignition coil and spark plug on cylinder 4 (swap with another cylinder to isolate the fault).
5. If the injector is confirmed faulty, replace it. Genuine (OE) BMW parts or quality equivalents are recommended.
6. For mechanical problems (low compression), more extensive repair is required (piston ring, valve replacement, etc.) depending on diagnostic results.

Tools needed: diagnostic scanner (ISTA, INPA), multimeter, compression tester, tool set for removing injectors and ignition coils.

Knock-On Problems

Ignoring P0272 and continuing to drive with a misfire in cylinder 4 can lead to the following:

• Catalytic converter overheating from unburned fuel entering the exhaust, which can destroy the converter.
• Increased wear of cylinder and piston components from incomplete combustion and higher loads.
• Ignition coil or spark plug failure from constant misfires.
• Worse emissions and a measurable drop in fuel economy.

Get the repair done as soon as possible to avoid costly damage.