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In this automotive repair guide, we will tackle how to replace the power electronic module on a Mercedes- Benz S-Class. The repair consists of removing parts of the exhaust system to get access to the module and removing the electrical connectors and module itself.

Table of Contents

The parts for this repair will include a new module, and some specialty tools may be required.

Disclaimer: These instructions are for information purposes only. 




  1. Use a professional diagnostic scanner to disable the high voltage battery. Select Control Units then Battery Management System (BMS). Under the BMS unit, you will find the option to disable the high voltage battery. bms scanner


  2. Disconnect the negative terminal of the battery in the trunk using a 10mm socket.
  3. Remove the hybrid battery cover on the top left of the engine bay by the windshield cowl exposing the hybrid battery.
  4. Make sure to wear rubber electrical insulated gloves when doing any repair on a high voltage system. Disconnect the electrical connector from the hybrid battery.
  5. Use a ratchet and 10mm socket to unbolt the orange high voltage cable. Unplug the high voltage cable from the hybrid battery. Set it aside and make sure it doesn't come in contact with the battery. Lock or cover the contacts on the high voltage battery. disconnect high voltage battery


  6. Disconnect the O2 sensor electrical connectors. o2 sensor disconnect


  7. Remove the upper 13mm bolt on the exhaust header flange. remove catalytic converter


  8. Use a ratchet, extensions, and a 13mm socket to unbolt the lower bolt that secures the catalytic converter to the exhaust header flange. Use a 10mm ratchet and socket to unbolt the bracket mounted to the vehicle. remove catremove catremove cat


  9. Unbolt the clamp around the exhaust pipe and slide it over the joint. exhaust clamp
  10. Remove the two 10mm nuts and bracket at the middle of the pipe. exhaust pipe


  11. Pry the rubber exhaust hanger off the attached hanger and work the piece of exhaust out from under the vehicle. Set it aside.remove ruber gromet

    remove the catalytic converter

  12. With a 7mm flexible ratcheting wrench, unbolt the three bolts holding the heat shield around the exhaust headers. There are a couple of heat shields that need to be removed. The easiest way to remove the bolts that hold these shields is to use a flexible ratcheting wrench.heat shield boltsA couple of the bolts are easier to remove from above the engine. Remove the heatshields.heat shieldheat shield bolts
  13. For safety, remember to wear insulating gloves and locate the hybrid converter control module and make sure to remove the interlock circuit breaker with a hex bit on a driver.interlock screw


  14. Remove the cooling hoses from the module with a pair of pliers and plug the hose with a bolt, extension, or plug to prevent coolant from leaking out. Note that you will lose a small amount of coolant. Draining the coolant is not necessary. Bend the hose before removal to minimize coolant loss. Then plug the end of the hose and continue with the removal of the power electronic module.  Two hoses need to be disconnected. One is the inlet, and the other is the outlet hose. The power electronic inverter uses an engine coolant to cool down. coolant hose


  15. Remove the lower 13mm bolt for the engine mount on the passenger side. Place a block of wood under the engine and raise the engine about two inches. This will allow you to get to disconnect the power electronic module and slide it out. Do not raise the engine too high, or you risk causing damage. 
  16. Unbolt the cooling hose elbow from the bottom of the module with a Torx bit and remove it to get access to the bolts holding the electrical connectors.
  17. Unbolt the electrical connectors from the module and get them out of the way.
  18. You will now have access to the 4 bolts holding the converter module on the motor. Use a 13mm socket and ratchet to remove the 4 bolts from the module. Two can be accessed from the top and two from the bottom. One of the bolts will also hold the ground wire to the module.
  19. Pull the module down and unbolt the two 10mm nuts connecting the high voltage cable to the module. Pull the clip from the high voltage connector and unplug the cable from the module.Mercedes Power Electronic Module
  20. Work the module down and out of the vehicle and remove it.
  21. Follow the procedure in reverse order to replace it with a new hybrid voltage converter control module.
Always use proper PPE when working on a hybrid vehicle. Follow proper service procedures and safety regulations when working on electric vehicles. Proper hybrid automotive electrical training is important, and disregarding the safety precautions of working on a high voltage system can lead to shock, injury, and death.

My hybrid warning light is still on. What do I do?

A professional OBDII scan tool will be needed to access the hybrid modules to clear the diagnostic trouble codes on the vehicle's computer. Alternatively, the vehicle can be taken to the dealer, and for a fee, the computer will be reset and codes cleared.

Additional Pictures 

power inverterbattery connector hybridmercedes hybrid catalytic convertercat heat shield
Mercedes Benz S400 Power Electronic Module Replacement Guide In this automotive repair guide, we will tackle how to replace the power electronic module on a Mercedes- Benz S-Class. The repair consists of removing parts of the exhaust system to get access to the module and removing the electrical connectors and module itself.