BMW M47 Injector Problems: Symptoms, Faults & Repair Guide (UK)

The M47 was BMW's first mass-market 4-cylinder diesel, powering the E46 320d and E87 118d/120d. The turbocharged unit uses Bosch solenoid injectors and is known for strong performance but age-related injector wear on surviving examples.

Common M47 injector failure symptoms

• Rough idle and vibration: Worn M47 injectors create uneven idle due to nozzle erosion after high mileage.
• Loss of power and flat spots: Reduced injection volume from worn nozzles causes hesitation and power loss.
• Black smoke on acceleration: Over-fuelling from degraded nozzles produces visible black smoke.
• Engine management light: Fault codes stored for injector circuit faults (P0201-P0204).

Why M47 injectors fail

• fuel contamination
• high-pressure wear cycles
• carbon buildup
• poor fuel quality
• internal valve wear

How to diagnose M47 injector faults

1. Read fault codes: Connect an OBD-II scanner and note any injector-related codes (P0201–P0204, P2146, P2149). This identifies which cylinder is affected.
2. Perform a leak-off test: Disconnect the fuel return pipes and route into measuring containers. Run the engine at idle for 60 seconds. Compare volumes per cylinder against manufacturer spec.
3. Listen for injector tick: Use a mechanic's stethoscope on each injector body. A dead or irregular tick indicates a stuck or failing solenoid.
4. Check fuel rail pressure: Monitor live fuel rail pressure data via diagnostic tool. Low pressure can mimic injector symptoms and may indicate a fuel pump issue instead.
5. Inspect for external leaks: Check around injector seals for signs of fuel or combustion gas leakage. Black carbon deposits indicate a blown seal.
6. Cylinder balance test: Use diagnostic software to run a cylinder contribution test. This electronically disables each injector in turn to measure its effect on engine speed.

Fault codes linked to M47 injector issues

• P0201-P0204 – Injector circuit malfunction
• P0087 – Fuel rail pressure too low
• 30BA – BMW-specific: Cylinder injection cutoff

M47 repair advice

M47 injectors use solenoid technology and are simpler than N47 piezo units. Coding is not required on most M47 variants. Torque to manufacturer specification.

M47 injector replacement cost (UK)

• Per injector: £180 - £350
• Full set: £700 - £1,200
• Labour: £120 - £300

Compatible injector part numbers for M47

• Bosch 0445110131 – Bosch solenoid injector for M47TU2
• Bosch 0445110080 – Earlier M47TU variant
• BMW 13537793836 – BMW OE reference

Vehicles using the M47 engine

• BMW 320d (1998-2005)
• BMW 118d/120d (2004-2007)
• BMW 318d/320d (2004-2007)
• BMW 520d (2005-2007)

Find your exact M47 injector by registration

Frequently asked questions

Do M47 injectors need coding?

Most M47 variants do not require electronic coding. The injectors are plug-and-play.

How much does M47 injector replacement cost?

A set of four remanufactured M47 injectors costs £300-£500. Labour is 2-3 hours.

Is the M47 the same as the N47?

No. The M47 is the predecessor. It uses solenoid injectors while the N47 uses piezo technology.

How much does it cost to replace injectors?

Replacement typically costs £150–£350 per injector depending on brand and engine. A full set of four with professional fitting usually costs £600–£1,200.

Can I drive with a faulty injector?

Driving with a faulty injector can cause engine damage, increased fuel consumption, DPF contamination, and oil dilution. We recommend diagnosis and replacement as soon as possible.

Do new injectors need coding?

Some vehicles require injector coding after replacement using manufacturer-specific diagnostic tools. Many Bosch solenoid units are plug and play. Check your engine guide for specific requirements.