Skip to content
GTECH Calibration
Portal

P0301

Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable), Incorrect ignition timing, Vacuum leak(s), Low or weak fuel pressure, Improperly functioning EGR system, Defective Mass Air Flow Sensor, Defective Crankshaft and or Camshaft Sensor, Defective Throttle Position Sensor, Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems).

  • Audi
  • Powertrain
  • Generic code
  • High severity

How this code is built

P
SystemPowertrain
0
Defined bySAE, the same on every car
3
AreaIgnition system or misfire
01
FaultThe specific fault in that area

What it means

P0301 means the engine control unit has detected a misfire on cylinder 1. It monitors crankshaft speed fluctuations and saw cylinder 1 failing to contribute its share of power, either constantly or intermittently. On Audi engines the cause is most often ignition related, but fuel, air and mechanical faults can also set it.

Symptoms

  • Engine management light on, flashing if the misfire is severe
  • Rough or uneven idle
  • Hesitation, jerking or loss of power under acceleration
  • Hard starting or occasional stalling
  • Smell of unburnt fuel from the exhaust
  • Increased fuel consumption

Possible causes

  • Worn or faulty spark plug on cylinder 1likely
  • Failed ignition coil on cylinder 1likely
  • Faulty or leaking fuel injector on cylinder 1, or low fuel pressurepossible
  • Vacuum or intake air leak affecting cylinder 1 (split hose, leaking intake manifold seal)possible
  • Wiring or connector fault on the cylinder 1 coil or injector circuitpossible
  • Mechanical problem on cylinder 1 such as low compression, valve damage or head gasket leakrare
  • Faulty crankshaft or camshaft sensor, or incorrect timing, affecting misfire detectionrare

How to diagnose

  1. Read all stored codes and freeze frame data to see load, rpm and temperature when the misfire occurred, and check whether other cylinders also show misfires.
  2. Inspect the cylinder 1 coil connector, wiring and plug for damage, oil, moisture or corrosion.
  3. Check the spark plugs for wear, correct type and gap where applicable, and compare cylinder 1 with the others.
  4. Swap the cylinder 1 coil with another cylinder, clear the codes and see whether the misfire follows the coil.
  5. Swap the cylinder 1 spark plug with another cylinder in the same way if the coil is not at fault.
  6. Check for intake leaks by inspecting hoses and seals, and review fuel trim values and fuel pressure against the manufacturer's specification.
  7. Test the cylinder 1 injector for correct resistance and operation, and listen for or check its pulse.
  8. Carry out a compression or leak-down test on cylinder 1 if the ignition and fuel side check out; procedure and limits depend on the engine.

How to fix

  • Replace the spark plugs as a set with the correct specification for the engine.
  • Replace the faulty ignition coil.
  • Repair or replace damaged wiring or connectors on the cylinder 1 circuits.
  • Replace or professionally clean and test the faulty fuel injector, and correct any fuel pressure fault.
  • Repair the vacuum or intake leak by replacing the failed hose or seal.
  • Carry out the necessary engine repair if compression is low, such as valve or head gasket work.

Can I keep driving?

High severity

Avoid driving if the engine management light is flashing, as unburnt fuel can overheat and damage the catalytic converter. If the light is steady and the misfire is mild, drive gently a short distance to get it repaired promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

Nearby codes