P1147

What it means

P1147 on a Volkswagen means the engine control unit has seen the bank 2 fuel trim correction reach its limit on the lean side. The lambda control cannot add enough fuel to bring the mixture back to target, so the system is judged too lean. Bank 2 is the side of the engine that does not hold cylinder 1, and the exact layout depends on the engine.

Symptoms

• Engine management light on
• Rough idle or unstable idle speed
• Hesitation or flat spots under acceleration
• Poor fuel economy or reduced power
• Occasional misfire or lean-running hiccup at light load

Possible causes

• Unmetered air entering after the air mass meter on the bank 2 side, such as a split intake hose, loose clip or leaking intake manifold gasketlikely
• Vacuum leak from a perished vacuum hose, brake servo hose or crankcase breather hose and its connectionslikely
• Exhaust leak upstream of the bank 2 oxygen sensor letting in air and giving a false lean readingpossible
• Faulty or contaminated bank 2 oxygen sensor, or damaged sensor wiring or connectorpossible
• Low fuel pressure or restricted fuel delivery, or a partly blocked or leaking bank 2 injectorpossible
• Dirty or inaccurate air mass meter causing wrong load calculationpossible
• Faulty crankcase ventilation valve or leaking engine oil filler cap or dipstick sealrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, engine speed, temperature and fuel trim values when the fault set
2. Check for other codes such as bank 1 lean, misfire or air mass meter faults, as these point to a shared cause
3. Visually inspect intake pipework, clips, vacuum hoses and breather hoses for splits, loose fittings and oil soaking
4. Look at live fuel trims at idle and at about 2500 rpm; a lean trim that improves at higher revs suggests a leak, while one that worsens suggests a fuel delivery problem
5. Carry out a smoke test of the intake system to find unmetered air leaks
6. Inspect the exhaust upstream of the bank 2 oxygen sensor for leaks, blowing gaskets or cracked manifold joints
7. Check the bank 2 oxygen sensor wiring, connector and live readings against the specification for your engine
8. Measure fuel pressure and check injector operation and the air mass meter reading, following the procedure for the specific engine

How to fix

• Replace split or loose intake hoses and refit clips, or replace the intake manifold gasket as needed
• Renew perished vacuum or breather hoses and any faulty crankcase ventilation components
• Repair the exhaust leak with new gaskets or sections of pipe as appropriate
• Replace the bank 2 oxygen sensor or repair damaged wiring and connectors if testing proves it faulty
• Restore correct fuel delivery by replacing a weak pump, a blocked filter where fitted, or a faulty injector as found
• Clean or replace the air mass meter if it reads incorrectly

Can I keep driving?

Nearby codes

• P1146VolkswagenMass Or Volume Air Flow Circuit Power Supply Malfunction
• P1148VolkswagenOxygen Sensor Control Bank 2 System Too Rich