P03E4

What it means

P03E4 means the engine control unit has judged that combustion in cylinder 8 is not meeting the expected performance. How it judges this depends on the engine. It may use crankshaft speed variation, knock or ion-current sensing, or in-cylinder pressure data. The cause may be ignition, fuel, air or mechanical, so related misfire or fuel trim codes should be read alongside it.

Symptoms

• Engine management light on, possibly flashing under load
• Rough running or a noticeable shake, especially at idle
• Hesitation, loss of power or poor acceleration
• Increased fuel consumption
• Uneven or lumpy exhaust note, or a fuel smell from the exhaust
• Hard or extended cranking on start-up

Possible causes

• Worn or faulty spark plug or ignition coil on cylinder 8likely
• Faulty, blocked or leaking fuel injector on cylinder 8likely
• Damaged wiring, poor connector contact or corrosion at the cylinder 8 coil, injector or related sensorpossible
• Intake air leak or carbon build-up affecting cylinder 8 airflowpossible
• Valve train or variable valve timing fault, or a cylinder deactivation mechanism fault, on engines that have itpossible
• Low compression from worn rings, burnt or sticking valve or head gasket leak at cylinder 8possible
• Faulty crankshaft position sensor or in-cylinder sensor giving false readingsrare

How to diagnose

1. Read all stored and pending codes plus freeze frame data, noting engine load, speed and temperature when the fault set, and check for misfire, fuel trim or cam timing codes.
2. Inspect the cylinder 8 coil, plug connector, injector connector and wiring for damage, oil contamination, corrosion or loose fit.
3. Remove and inspect the cylinder 8 spark plug for wear, fouling, oil, fuel or abnormal deposits, comparing it with other cylinders.
4. Swap the cylinder 8 coil with another cylinder, clear the codes and see whether the fault follows the coil, if the engine layout allows.
5. Check live data for misfire counters and fuel trims, and look for unusual cylinder 8 readings.
6. Test injector operation on cylinder 8 by checking its resistance, electrical drive signal and spray or flow, following the manufacturer's procedure.
7. Smoke-test the intake for air leaks and check for vacuum leaks near cylinder 8.
8. Carry out compression and leak-down tests on cylinder 8 if electrical and fuel checks are clear, and check valve timing and valve train operation where the engine design requires it.

How to fix

• Replace the worn spark plug, or the faulty ignition coil, on cylinder 8, using the specified type.
• Replace or professionally clean and test a faulty cylinder 8 injector.
• Repair damaged wiring or connectors, or replace the affected harness section.
• Repair intake leaks and clean carbon deposits using a method suited to the engine.
• Repair or replace faulty valve train, variable valve timing or cylinder deactivation components as diagnosed.
• Carry out the necessary engine repair for low compression, such as valve, piston ring or head gasket work.

Can I keep driving?

Nearby codes

• P03E3GenericCylinder 8 Pressure Variation High
• P03E5GenericA Camshaft Position Actuator Position Sensor C Circuit Bank 1