The Quick Answer above is the generic definition. What follows is what is documented for the Mercedes-Benz models that log P0204, checked against manufacturer data and owner reports.
DTC/P0204·Mercedes-Benz
P0204 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Mercedes-Benz
P0204 on a Mercedes-Benz means the engine control unit detected an electrical fault (open circuit, short, or out-of-range resistance) in the wiring or driver for the cylinder 4 fuel injector. The injector itself may be fine while the wiring, connector, or ECU driver is at fault. Left unrepaired it causes a cylinder 4 misfire. Typical repair runs about 60 to 350 EUR depending on whether it is wiring or a replacement injector.
Repair cost on Mercedes-Benz€5 - €700
Connect any standard Bluetooth OBD2 adapter to your Mercedes-Benz and Skanyx tells you what P0204 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
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Mercedes C-Class
2007-2024On OM651 and other CDI diesels the common-rail injectors are expensive and each carries a calibration code that must be written into the ECU after replacement, a job for XENTRY or a workshop. Petrol M274/M264 engines can throw P0204 from a corroded connector or chafed harness. Skanyx reads the circuit code and freeze frame but not the injector calibration data.
What causes P0204 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0204 page, these are the documented Mercedes-Benz-specific patterns:
Mercedes C-ClassCostly common-rail injector with calibration coding on OM651 CDI diesel
Mercedes C-ClassConnector corrosion or harness chafe on M274/M264 petrol
How to diagnose P0204 on a Mercedes-Benz with OBD2
Follow these steps to pinpoint the root cause of P0204:
- Read the stored code and freeze frame with Skanyx to confirm it is P0204 and note the conditions (RPM, load, coolant temp) when it set
- Check for companion misfire codes (P0300 or P0304) which point to a genuine combustion problem on cylinder 4
- Inspect the cylinder 4 injector connector and harness for corrosion, looseness, melted pins, or chafing
- With the engine off, measure the injector winding resistance with a multimeter and compare against the workshop spec (most petrol injectors read roughly 12-17 ohms)
- Check for the injector control and supply circuits with a multimeter or test light, and swap the suspect injector to another cylinder to see if the fault follows it
- Note that per-injector coding, flow balance, and quantity-correction values are not on generic OBD2 - read those with a brand tool such as Carly, OBDeleven, or XENTRY, or have a workshop verify them
How much does P0204 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0204 in EUR, compiled across makes. Expect Mercedes-Benz parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0204 on Mercedes-Benz
These codes commonly cluster with P0204 on Mercedes-Benz vehicles:
Looking for the full P0204 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0204 guideSkanyx · Mercedes-Benz
Diagnose P0204 on your Mercedes-Benz
Your car logged P0204. Skanyx reads it on any standard Bluetooth OBD2 adapter, tells you whether it is safe to keep driving, and shows the €5-€700 repair range so you know the number before a shop quotes you. Free on iPhone and Android, and you do not need to be a mechanic to read it.
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