Can a Mercedes detect a remap?

This brief article will explain performance maps in the Mercedes Benz engine control unit and answer the following questions: can a Mercedes detect a remap? Various ways to remap an ECU? And why remapping the engine control unit is not a  good thing for your car?

Can a Mercedes detect a remap?

No Mercedes cannot detect a remap to the engine control unit. When the vehicle is connected to a star diagnosis scanner, it can only read actual values of various sensors on the engine, stored and current fault codes and flash the engine control unit software. Performance maps cannot be checked or modified by star diagnosis.

Few petrol engines like M271, M274 allow for correction programming. Fuel injection quantity, idle rpm can be changed under fixed limits. Fuel mixture can be slightly enriched or enriched to compensate for any mixture adaptation variation but any further changes to the performance map to increase the power cannot be done.

Originally engines are in a slightly detuned state from the manufacturers to comply with emissions norms. Engine control units are usually remapped to extract more power from the engine by increasing boost pressure, fuel injection quality and fuel pressures etc.

Mercedes Benz AMG is a performance division of Mercedes Benz, AMG models are designed with performance as the main goal. If a customer wants more power, AMG models are available for every model series in the Mercedes Benz catalogue. Driving modes like sports, Sports Plus, Comfort and ECO come as standard in Mercedes Benz.

What is a Performance Map in the Mercedes Benz engine control unit?

The engine control unit in Mercedes Benz cars takes input from sensors like fuel pressure sensor, oxygen sensor, air mass, ambient air temperature sensor and based on defined parameters actuate the components like throttle valve, fuel injectors, ignition system. These defined parameters are called performance maps. 

There are multiple performance maps stored in the engine control unit depending upon the atmospheric pressure and temperature. The complete system is the closed-loop, lambda values are constantly monitored by ht ECU and adjusted on the fly if too much or too little oxygen is detected in the exhaust gases.

Ideally, performance maps consist of four different parameters as follows.

  • Basic parameters- it contains input values like accelerator pedal position, coolant temperature, intake air temperature, manifold pressure and crankshaft position.
  • System parameters- Airmass which is measured by air mass sensor or calculated according to intake manifold pressure and air temperature determines the engine load. Engine speed is determined by the crankshaft position.
  • Actuator parameter- it contains data for various throttle valve openings, injection timing, ignition timing in case of petrol engine and the start of fuel injection which can be advanced and retarded.
  • Control parameters- it contains feedback parameters like lambda values and knocks limits.

The engine control unit monitors these parameters when the engine is running and compares them with the data stored in the performance map. Mixture adaptation is initiated if the system parameter deviates from the stored data, if the control parameters are still out of range then EOBD malfunction is activated to warn the driver. A fault is stored along with fault freeze frame data in the fault memory of the engine control unit.

Various ways to remap Mercedes Benz ECU

Mercedes Benz engine control unit can be remapped using engine tuning tools to copy or modify performance data stored in the memory. In some cases, it might be necessary to open the engine control unit housing and replace the IC  chip (integrated circuit chip) containing the performance data with a new IC chip. 

Various aftermarket tools are available like K-TAG, auto tuner. A professional engine tuner creates a remap by dyno tests and saves it in the master unit of the tuner tool. This remap can be downloaded and flashed in the ECU of the same model from the SLave tuner unit. 

Remapping an ECU is considered as stage 1 of tuning, increase in power is not substantial and most remaps are done to change the exhaust sound of the vehicle.

A tuning box or piggyback ECU is available for Mercedes Benz ECU which cannot be flashed by aftermarket tools. A piggyback ECU modifies the input signal going into the engine control unit and tricks it into increasing boost or fuel pressure even in partial load conditions. 

Stage 2 and stage 3 Tuning requires changing parts of intake and exhaust systems. Larger turbochargers can also be installed along with replacing stock internal parts to compensate for increased power output. Brabus is a famous engine tuner for Mercedes Benz AMG cars as AMG no longer allows for ECU remaps and engine tuning.

Why avoid remapping Mercedes Benz?

Mercedes Benz engine components are precisely engineered to meet set standards and regulations. By remapping the ECU it is no longer possible to meet the same levels of comfort and performance. Remapping can also reduce the longevity of the engine as components are constantly operated under full load conditions.

CO2 emission values will not be the same as advertised and vehicles can fail emission tests which will incur hefty fines. Running an ECU remap exhaust component like a catalytic converter can be damaged and its efficiency to filter out harmful gases can reduce over time. 

EOBD malfunction can be continuously active in the instrument cluster since the lambda values deviate from factory specified values. Hence ECU remap must be avoided as the costs of repairs can be very expensive 

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Mercedes cannot detect an engine control unit remap but if the vehicle reports to the workshop for engine malfunction then comparing actual values of sensors to specified values can identify modification to the performance map. Warranty claims can be rejected in these cases as the vehicle operates outside of setting parameters designed by the manufacturer.

FAQs: Can Mercedes detect remaps?

Is an ECU remap worth it?

ECU remap is not worth it. If remap is unsuccessful ECU can get stuck in bootloader mode and cannot be programmed again.

Does ECU remap damage the engine?

It depends on the remap, if the changes made to the original map are not within legal limits then engines with good built quality will not be damaged.

Can dealerships detect a remap?

If a tuning box or piggyback ECU is installed then the dealership can easily detect remaps. Remapping by flashing the ECU software cannot be detected unless the vehicle is driven by a regular dealership technician.

Will ECU tune void my warranty?

Yes in most cases faults due to ECU tuning will void the warranty.

Does remapping save fuel?

Yes, performance maps can be designed to increase fuel economy. Eco and Comfort driving modes are also available in the vehicle which offers better fuel economy.