How much does it cost to replace OM642 injectors?

A full set of six remanufactured OM642 injectors costs £900-£1,500. Labour is 4-6 hours. Total cost including fitting typically ranges from £1,400-£2,200.

Do OM642 injectors need coding?

Yes. Each piezo injector has a unique code that must be programmed via Star Diagnostic or compatible tool.

Can I replace just one OM642 injector?

Yes, but the V6 is sensitive to injector balance. If the vehicle has high mileage, consider replacing the full bank (3 injectors) at minimum.

Why are OM642 injectors more expensive?

The OM642 uses piezo technology which is more complex and expensive than solenoid injectors. There are also 6 injectors instead of 4.

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.

Why is my diesel injector knocking?

Diesel injector knocking is typically caused by worn nozzle tips that alter the fuel spray pattern, leading to harsher combustion. Carbon buildup, incorrect injection timing, and high fuel pressure can also contribute. A professional leak-off test can confirm whether injectors are the cause.

Can a bad injector cause white smoke?

Yes. A faulty injector that dribbles fuel instead of atomising it causes incomplete combustion, producing white or grey smoke. This is especially noticeable on cold starts and typically clears as the engine warms up.

How long do diesel injectors last?

Most diesel injectors last between 80,000 and 150,000 miles depending on fuel quality, driving conditions, and maintenance. Regular fuel filter changes and using quality diesel can extend their lifespan.

Will injector cleaner fix misfire?

Injector cleaner may help with minor carbon deposits, but it cannot fix worn nozzles, failed solenoids, or internal seal leaks. If misfire persists after using cleaner, professional testing and likely replacement is needed.

Mercedes OM642 V6 Injector Problems: Symptoms, Faults & Repair (UK)

Updated for 2026 diagnostics & repair guidance

Higher replacement cost than OM651 4-cylinder; 6 injectors vs 4.

The OM642 is Mercedes' long-running 3.0-litre V6 diesel, found across the ML, GL, S-Class, E-Class, and Sprinter. Its six Bosch piezo injectors are expensive to replace but critical to the engine's smooth operation and low emissions.

OEM tested & calibrated12-month warrantyFree UK deliveryNo coding required (most models)

OEM Tested
12-Month Warranty
Free UK Delivery

Registration Lookup Find Matching OM642 Injector

Drivers also ask

Quick Diagnosis

If your OM642 engine shows:

rough idle
hard starting
white or black smoke
knocking or ticking noise
reduced fuel economy

A faulty injector may be the cause. Continue below to confirm symptoms and solutions.

Can You Drive With This Problem?

Driving short distances may be possible, but continued use can cause:

piston damage
turbo contamination
fuel dilution of engine oil
catalytic converter damage

Prolonged driving may lead to major engine failure.

Typical Repair Costs (UK)

Average costs for injector-related repairs:

£180 - £350

Per Injector

£700 - £1,200

Full Set (4)

£120 - £300

Labour

Early replacement prevents costly engine damage.

Common Injector Failure Symptoms

Owners frequently report:

Rough idle and V6 imbalance

The V6 is normally very smooth — any injector fault creates noticeable vibration due to bank-to-bank imbalance.

Blue/white smoke from exhaust

Piezo injectors that dribble fuel cause incomplete combustion and visible exhaust smoke.

Reduced power in Sport mode

The ECU limits boost and fuel when injector deviation is detected, most noticeable in Sport.

Engine management light with bank codes

Fault codes often reference a specific bank (1 or 2) rather than individual cylinders.

Oil dilution by diesel

Severe injector leakage allows fuel past piston rings, raising the oil level on the dipstick.

Full symptom guide White smoke guide

Fault Codes Linked to Injector Issues

Common diagnostic codes include:

P0201-P0206Injector circuit malfunction (cylinders 1-6)

P2146Fuel injector group A supply voltage circuit

P2149Fuel injector group B supply voltage circuit

P0087Fuel rail system pressure too low

Misfire diagnosis guide

How to Diagnose OM642 Injector Faults

Follow this step-by-step testing approach to identify the faulty injector:

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.

Full leak-off test guide Injector coding guide

Why OM642 Injectors Fail

Common causes include:

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

Professional remanufacturing restores spray pattern and pressure accuracy.

When Replacement Is Required

Injector replacement is recommended if:

leak-off test fails
misfire persists after coding
excessive return flow detected
spray pattern fails testing
vehicle enters limp mode

OM642 Repair Advice

The OM642 uses 6 piezo injectors which require coding via Star Diagnostic. The V6 layout means bank 2 injectors are harder to access — budget 4-6 hours labour for a full set.

Remanufactured (Recommended)

OEM-spec rebuild with new nozzles, seals, and solenoids. Full flow testing. 12-month warranty. 40–60% less than new.

Brand New OEM

Factory-fresh from Bosch, Delphi, or Siemens. Highest cost but zero previous wear. Best for low-mileage vehicles.

Vehicles Using the OM642 Engine

This engine is commonly found in:

Mercedes-Benz ML 350 CDI

W164/W166 · 2009-2015

Mercedes-Benz GL 350 CDI

X164/X166 · 2009-2015

Mercedes-Benz S 350 CDI

W221 · 2009-2013

Mercedes-Benz E 350 CDI

W212 · 2009-2016

Mercedes-Benz Sprinter 519 CDI

W906 · 2009-2018

Mercedes-Benz CLS 350 CDI

C218 · 2010-2017

Professional Installation Tip

Always:

replace copper sealing washers
torque injectors to manufacturer specification
clean injector seats before installation
code injectors after installation (if required)

Leak-off test guide Injector coding guide

Compatible Injector Part Numbers for OM642

The following injector part numbers are commonly associated with OM642 engines:

Bosch

0445115064

Bosch piezo injector for OM642

£235.00View details

Bosch

0445115027

Earlier OM642 variant

£235.00View details

Also commonly fitted:

A6420701187Mercedes-Benz

These injectors are commonly used with the OM642 engine. Confirm compatibility using your engine code or registration lookup before ordering. Our team can verify the correct part for your specific vehicle.