Kodowanie wtryskiwacza (IMA) Mercedes OM654: czy trzeba?

Yes — a used injector on the Mercedes OM654 must be coded to the ECU. Every OEM injector carries an individual calibration code (Mercedes calls it IMA) printed on its body. That code has to be written into the engine ECU with STAR/Xentry or an equivalent diagnostic tool so the ECU knows the injector's exact flow characteristics. Skip it and the engine will run rough.

This one step is the most common thing DIYers miss when fitting a used injector. Here's what IMA is, where to find the code, and what coding actually involves.

What is IMA / injector calibration coding?

No two diesel injectors deliver fuel exactly alike. During manufacture, each injector is measured and given an individual calibration code that describes tiny differences in its flow at different pressures. On Mercedes engines this is known as IMA (Injektor-Mengen-Abgleich — injector quantity calibration).

The engine ECU uses that code to fine-tune how long it holds each injector open, so all cylinders deliver precisely the intended amount of fuel. Without the correct code, the ECU is working from the wrong assumptions for that injector — and combustion on that cylinder is slightly off on every stroke.

Where is the IMA code printed?

The calibration code is laser-etched or printed directly on the injector body, usually near the electrical connector alongside the Bosch 0445… number and the Mercedes A-number. It's a short string of letters and digits — easy to overlook and easy to misread, so clean the body and photograph it in good light.

Because the code lives on the injector itself, a used injector already carries its own valid IMA code. You're not inventing a number — you're reading the code off the part you fitted and entering it into the ECU for the correct cylinder. If you're unclear which markings are which, our Bosch 0445 vs Mercedes A-number guide shows what's etched where.

Do you need coding for a used injector specifically?

Yes, and arguably more so than for a new one. A used injector comes from a different engine with its own calibration, so its IMA code will almost never match the value currently stored for that cylinder in your ECU. You must overwrite the old value with the new injector's code. The good news is that the used injector carries everything you need — the code is right there on the body.

How is the injector coded to the ECU?

Coding is a software procedure, not a mechanical one:

1. Connect a diagnostic tool that supports Mercedes injector coding — Mercedes STAR/Xentry, or a capable independent tool with the same function.
2. Navigate to the engine control unit's injector calibration function.
3. Enter the IMA code from the new injector for the exact cylinder you replaced.
4. Save/write to the ECU and clear related fault codes.
5. Road test and re-check per-cylinder correction values to confirm the cylinder is now balanced.

In general terms this is a short workshop job — a matter of minutes on the software side once the injector is physically fitted — but it does require the right equipment. If you don't own a suitable tool, most independent Mercedes specialists and many general garages can code an injector quickly. Expect a modest labour charge rather than a major bill; ask your garage to confirm before booking.

What happens if you skip coding?

Skipping IMA coding doesn't stop the car from starting, which is exactly why it catches people out. But the ECU runs the new injector on the wrong calibration, so you'll typically get rough or uneven running, a slight misfire feel, possibly more smoke or noise, and stored fault codes. It can also upset emissions and DPF behaviour over time. In short: the injector may be perfect, but without coding the car won't run right. Always plan the coding step into the job before you order the part.

Ready to source one? Our OM654 injectors — A6540700300 / 0445118034, the piezo A6540730087 / 0445118009 and A6540700187 / 0445117048 — all show their body markings in the listing photos, so you can read the IMA code before you buy. Before ordering, make sure the injector is the fault using our OM654 symptoms guide, and check the part on arrival with our used-injector inspection guide. Everything ships EU-wide from Bulgaria in 3–7 days with a 14-day return.

FAQ

Can I code the injector myself?

Only if you have a diagnostic tool that supports Mercedes injector calibration. A basic code reader won't do it — you need STAR/Xentry or an equivalent that can write IMA values to the ECU.

The used injector already has a code — do I still enter it?

Yes. The code on the body is its calibration, but your ECU still stores the old injector's value for that cylinder. You must write the new injector's code into the ECU so they match.

Will the car run at all without coding?

Usually it will start and drive, but it will run rough, may smoke or misfire, and will likely log fault codes. Coding is required to make the repair correct, not optional.