P039E

What it means

P039E means the engine control unit has judged that combustion in cylinder 1 is not performing as expected. It typically sets this by comparing crankshaft speed or other combustion feedback for that cylinder against what it expects. The exact detection method and thresholds depend on the engine and manufacturer.

Symptoms

• Engine management light on, possibly flashing under load
• Rough idle or noticeable shaking
• Hesitation or loss of power when accelerating
• Hard starting or an uneven cold start
• Increased fuel consumption
• Smell of unburnt fuel from the exhaust

Possible causes

• Worn or fouled spark plug on cylinder 1likely
• Faulty ignition coil or coil driver on cylinder 1likely
• Faulty, blocked or leaking fuel injector on cylinder 1likely
• Damaged wiring or poor connector contact to the cylinder 1 coil or injectorpossible
• Intake air leak or carbon build-up affecting cylinder 1 (depends on engine design)possible
• Low compression on cylinder 1 from a valve, piston ring or head gasket faultpossible
• Fault in the control unit or in a cylinder combustion sensor, where fittedrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data (load, rpm, coolant temperature) to see when the fault occurs, and look for related misfire or injector codes.
2. Check live data for cylinder 1 misfire counts or speed deviation at idle and under light load.
3. Inspect the wiring and connectors to the cylinder 1 coil and injector for damage, corrosion, oil contamination or looseness.
4. Remove and inspect the cylinder 1 spark plug for wear, fouling, wet fuel or oil, and check the gap against the manufacturer's specification.
5. Swap the cylinder 1 coil with another cylinder, clear the codes and see whether the fault follows the coil.
6. Test the cylinder 1 injector for correct resistance, operation and spray or flow, following the procedure for that engine.
7. Smoke test the intake system and check for vacuum leaks near cylinder 1.
8. Carry out a compression or leak-down test on cylinder 1 and compare with the other cylinders.

How to fix

• Replace worn or fouled spark plugs, usually as a full set.
• Replace the faulty ignition coil on cylinder 1.
• Clean or replace the faulty fuel injector on cylinder 1 as the test results indicate.
• Repair damaged wiring or connectors in the affected circuit.
• Repair intake leaks and remove carbon deposits in line with the manufacturer's procedure for that engine.
• Carry out the necessary engine mechanical repair if compression is low.

Can I keep driving?

Nearby codes

• P039DGenericCylinder 1 Pressure Variation High
• P039FGenericCylinder 2 Pressure Sensor Circuit