Mercedes Hybrid Vehicle No Start Problem

Mercedes-Benz hybrid vehicles such as S400 are notorious for having hybrid issues that lead to no-start engine conditions.

DIY Cost: $5500-$11500
Est. Time: 6-8 hr
Difficulty: Difficult

The most common Mercedes-Benz hybrid problems that won't allow you to start the engine are caused by either a faulty power electronic module (part number 0009064703) or a defective hybrid battery

At the time of this article, we have diagnosed five Mercedes-Benz S400 vehicles with no start problems.

We found that three of them wouldn't start due to the failure of the Power Electronic module. Two would not start due to the failure of the high voltage hybrid battery. 

Symptoms

mercedes s400 won't start

Symptoms of a faulty power electronic module on a Mercedes-Benz S400 Hybrid. 

  • The vehicle won't start.
  • Vehicle starts intermittently
  • Dash lights, ignition turn on car won't start. 

To diagnose Mercedes-Benz problems, you will need a good scanner such as factory Mercedes known as Star Diagnostic (DAS) with Xentry.

Aftermarket scanners that are also  good choices include:

  1. TopDon ArtiDiag 100
  2. Launch All System Scanner
  3. Autel MaxiCOM

Whatever scanner you use, it has to show factory codes, NOT generic P codes.

Codes like N129/1 and so on (a  letter, a number, and a dash). It also has to read the lithium battery's separate cell voltage and talk to the "inverter" and "power supply unit."

Power Electronics Module

Based on the experience of the YOUCANIC automotive team, the most common problem on the Mercedes-Benz S400 Hybrid is the power electronic module (sometimes called power inverter).

The function of this module is to receive commands from hybrid ECM via CAN-BUS Network and control inverter energy flow to and from the battery and engine. It can control the speed and timing of an electric motor in unison with an Internal combustion engine. It also controls and monitors other components like battery, charging, and other related modules. 

Mercedes power electronic module

The power electronic module should not be confused with the DC/DC converter.  Location of mercedes power electronic moduleThe power electronic module is mounted on the engine's side, below the right exhaust manifold on the passenger side. 

0009064703 damaged mercedes benz hybrid s400 power electronic module no start

The three-phase electrical motor often melts, which means that you can no longer start the engine since the electrical motor is used for starting. Remember that the S400 hybrid has no starter; instead, it uses the electric motor mounted in front of the torque converter.  

install power electronic module

Replacing the Power Electronic Moule at a Mercedes-Benz dealership costs between $11,500 and $15,000.

Mercedes power electronic module

It is much more affordable to buy a used or refurbished Power Electronic module on eBay at around $2000-$3000 and installed by an independent mechanic.

For more help, see: How to replace the Mercedes-Benz Power Electronic module. 

A used or refurbished power electronic unit does not need to be programmed. Fault codes will need to be cleared with a good Mercedes-Benz scanner. 

Mercedes power electronic module

The power electronic module is mounted on the side of the transmission housing on the passenger side. 

Mercedes hybrid won't start

The fault codes will be stored in Power Electronic Module (SG-EM) and Engine Control Unit (ECU):

  • U011000 - Communication with control unit Electric machine A has a malfunction.

  • U011081 - Communication with control unit Electric machine A has a malfunction. Incorrect data were received.

These codes are triggered by a faulty power electronic module. You can buy a refurbished power electronic module (0009064703) on eBay at half the dealer price.

The following part numbers are often associated with the power electronic module.

  • 0009064703 / 0009065802 / A0009065802
  • A 000 906 58 02, 0005844147 / A0005844147
  • A 000 584 41 47, 2213430400 / A2213430400,
  • 2213430300 / A2213430300, A2213431100,
  • 2213430900 / A2213430900, 2213430500,
  • 2213400400 / A2213400400, 2213400300
  • A2213400300, 2213400600 / A2213400600
  • 2213400500 / A221340050

Mercedes-Benz has issued a few different numbers for the power electronic module as the unit has gone over multiple revisions. 

Follow this guide to learn how to replace Mercedes-Benz power electronic module

Other reasons why your S400 hybrid may not start can also  be due to:

  • Hybrid battery failure
  • The inverter is located under the right side fender. 
  • Faulty A/C compressor

To find out why your S400 Hybrid won't start, you must read the Battery Management System module's fault codes. It is also important to run a full system scan to determine fault codes in other modules. 

The reason why your Mercedes-Benz S-Class won't start could also be: 

  • Ignition Switch -  EIS,
  • Intelligent Servo Module - ISM, 
  • Engine Control Unit - ECU

Hybrid Battery

bad hybrid battery youcanic mercedes hybrid s400

The second most common problem with the Mercedes-Benz S400 Hybrid is the failure of the hybrid battery, which is explained in detail here. 

There are two (2) types of electrical systems being implemented in a hybrid system. One is the 12 volts electrical system which is powered by 12 volts onboard battery. The 12-volt system powers almost 90 percent of the car, including lights, entertainment, horn, etc.

The high voltage electrical system is powered by a high voltage battery with>100 volts DC.

A hybrid Battery or High Voltage battery, or HV battery, is the powerhouse of the Hybrid’s electric motor.

Its main purpose is to power the Hybrid electric motor to help the Internal combustion engine with its load. It also acts as a starter for the Internal Combustion Engine. For an Internal Combustion Engine to start, the HV battery should at least have 15% of charge. You can check the charge level via the command by going to System > Hybrid Charge. 

Common fault codes that show up as stored or current in the battery management module (SG-BMS):

mercedes power electronic module
  • 180F00 - The high voltage battery has a malfunction during the recovery phase. 
  • 0BBD00 - The limit value for the difference between cell voltages in the high voltage battery module has been exceeded. 
  • 0BBE00 - The cell voltages in the high voltage battery module are different. 
  • 0A7D00 - The charge level of the high voltage battery module is low. 
  • 180C00, 180500 - The hardware monitoring function has detected a fault in the control unit. 
  • 0A1F04 - There is an internal fault in the control unit Battery. There is an internal fault. 
  • 0AE886 - The temperature sensor D of the high voltage battery has an electrical fault. There is an incorrect signal. 
  • 0ACA86 - The temperature sensor C of the high voltage battery has an electrical fault. There is an incorrect signal. 
  • 0AC586 - The temperature sensor B of the high voltage battery has an electrical fault. There is an incorrect signal. 
  • 0A9B86 - The temperature sensor A of the high voltage battery has an electrical fault. There is an incorrect signal. 
  • 0A1F96 - There is an internal fault in the control unit Battery. There is an internal component fault. 
  • 0A1F00 - There is an internal fault in the control unit Battery. 

DC/DC Converter

mercedes dc dc converter

Sometimes the DC to DC converter goes bad, but this failure is infrequent. When it fails, it can not transfer 130 Volt to 12 Volts and vice versa. 

Follow this guide to learn more about the Mercedes-Benz DC/DC converter and how to replace it. 

A/C Compressor 

hv-air-compressor

Another problem with the S400 is the AC doesn't work, which can prevent the engine start.

The AC compressor is the heart of the air conditioning system. In Internal Combustion engine cars, the engine can operate normally with a faulty AC compressor. In a Hybrid System, however, the refrigerant from the AC compressor's refrigerant serves as a cooling mechanism for the battery. A Hybrid AC Compressor is also operated by a High Voltage DC rather than a belt to a pulley on an Internal Combustion engine. The ECM protects the battery from overheating by monitoring the AC status and taking actions such as taking the CAN-BUS communication off when the problem is detected.

The AC compressor runs on high voltage, which means it is not belt-driven. There is a 60A inline fuse that is mounted on top of the transmission.

It is the yellow cable that runs from the hybrid battery to Power Electronic Module and AC compressor. The 60A fuse only protects the AC compressor, not the Power Electronic module. 

Service Campaign

It is important to note that Mercedes-Benz had issued a service campaign 2012080004 for this problem. We called to check with the dealer on several S400 Hybrids, and according to the service manager, the dealer performed the service for both cases.

Basically, the dealer verifies the part number. If the vehicle is equipped with the Power Electronics module's early model, the dealer replaces it free of charge. Our S400 had the "newer" version of the power electronic module, so the dealer did not replace the power electronic module. Yet, even the "newer" version of the power electronic module is still failing.

Because the Power Electronic module is mounted next to the exhaust manifold, the chances of the new unit failing again eventually remain high. 

Could you work on your Mercedes-Benz S-400 Hybrid on your own?

No. 

As explained in the sections above, there is a high risk of injury or death due to electric shock from the High Voltage System. Based on this, we only recommend that trained mechanics work on the high voltage hybrid system. 

Non- contact electric shock can also happen due to High voltage arc. Also, you have to buy expensive safety gear before you could work on the S-400 Hybrid. Below are a sample of procedures in just disconnecting the High Voltage System:

  1. Locate the onboard 12 volts battery.
  2. Disconnect 12v onboard battery ground line.
  3. Ensure that no voltage is passing from the charging point of the pre-fuse box and the ground by using a voltage tester.
  4. This would ensure that no transient voltage is stuck between the onboard battery and the auxiliary battery.
  5. It would also ensure that vehicle does not continue to be supplied by the auxiliary battery.
  6. Wear your protective equipment, including electric-resistant globes, an anti-arc jacket, and a helmet with a face shield.
  7. You can now disconnect the High Voltage connection from the high voltage battery module.
  8. Safely stick a tape on the High Voltage connector and, as much as possible, label it with a warning.

You may refer to this link for the complete instructions in disconnecting the HV System.

Should I buy a Mercedes-Benz Hybrid?

Mercedes-Benz hybrid vehicles are challenging to repair. Most auto mechanics will not repair these vehicles. We have even seen cases where a Mercedes-Benz dealership had difficulty diagnosing an S400 Hybrid vehicle. 

If you own a Mercedes-Benz S400 that won't start, make sure to find an expert that knows these vehicles.

It isn't easy to find auto mechanics that are trained to work on the Mercedes-Benz Hybrid system. Even Mercedes-Benz dealerships have a limited number of mechanics that can work on hybrid models. 

Working on the hybrid system can be dangerous since dealing with a high voltage (130 Volt) can cause injuries and death if you do not take the required precautions. 

Frequently Asked Questions

Are there any common problems with the power electronic module? Yes, burned-out circuit boards are the most common failures of these cars.

What are the common safety guidelines before working on a Hybrid Vehicle’s Power Electronic Module?

  1. The power electronic module is equipped with 3 or more high voltage capacitors, be sure to discharge capacitors to avoid electric shock.
  2. You can discharge an HV capacitor by shorting its negative and positive leads using a screwdriver, or you can also use a high resistor with a high Ohm rating and a plier.

How to diagnose a burned or faulty power electronic module using a scanner? Even if there is damage or burn to the board, the reader can access the module and determine the error.

ecm-read-faults
  1. Connect the scanner to the OBD port.
  2. Use Electronic Motor Control Unit Menu to check for faults.

How to disable a high voltage system?  You should disable the high voltage 120v System:

  1. Locate the onboard 12 volts battery.
  2.  Disconnect 12v onboard battery ground line.
  3. Ensure that no voltage is passing from the charging point of the pre-fuse box and the ground by using a voltage tester.
  4. This would ensure that no transient voltage is stuck between the onboard battery and the auxiliary battery.
  5. It would also ensure that vehicle does not continue to be supplied by the auxiliary battery.
  6. Wear your protective equipment, including electric-resistant globes, an anti-arc jacket, and a helmet with a face shield.
  7. You can now disconnect the HV connection from the high voltage battery module.
  8. Safely stick a tape on the HV connector and, as much as possible, label it with a warning.
  9. You may now connect the onboard battery for diagnostic procedures.

What are the common problems of a DC-to-DC converter?     • DC-to-DC converters can have a blown a fuse.     • It can have inverter failures that can cause a no-start.     • It can cause the battery not to charge.

How to diagnose a faulty DC-to-DC converter? You can use Scanner that can get into various control systems, reset errors and carry out some tests like Xentry Diagnostics, for example. How to diagnose a faulty HV Battery using a scanner.

  1. Plug the scanner into the OBD2 port.
  2. Go to SGBMS (Battery Management System) for a hybrid battery; you can check each cell's status and determine if the battery is faulty. 

What are the common problems with AC compressors that could affect the Hybrid operation? Any problem that would stop the AC from functioning, such as a blown fuse, is regarded by ECM as a severe error and would take out the CAN-BUS communication offline.

How would you know if the CAN-BUS communication is offline using a scanner? 1. Connect the scanner to the OBD2 port 2. Check the status of  “Hybrid CAN-BUS” it should be in an On status if everything is working. ECM will throw an Interlock circuit of the High Voltage On-Board Electrical System Has A Sporadic Malfunction error during maintenance since the HV system is disconnected. ECM will throw the same error if the power electronic module connector is disconnected or the fuse on top of the transmission is blown.

Could you work on your Mercedes-Benz S-400 Hybrid on your own?

No. As explained in the sections above, there is a high risk of injuries due to electric shock from the High Voltage System. Based on this, we only recommend that trained mechanics work on the high voltage hybrid system. 

Non- contact electric shock can also happen due to High voltage arc. Also, you have to buy expensive safety gear before you could work on the S-400 Hybrid.

Below are a sample of procedures in just disconnecting the High Voltage System:

Locate the onboard 12 volts battery.

  1.  Disconnect 12v onboard battery ground line.

  2. Ensure that no voltage is passing from the charging point of the pre-fuse box and the ground by using a voltage tester.

  3. This would ensure that no transient voltage is stuck between the onboard battery and the auxiliary battery.

  4. It would also ensure that vehicle does not continue to be supplied by the auxiliary battery.

  5. Wear your protective equipment, including electric-resistant globes, an anti-arc jacket, and a helmet with a face shield.

  6. You can now disconnect the High Voltage connection from the high voltage battery module.

  7. Safely stick a tape on the High Voltage connector and, as much as possible, label it with a warning.

You may refer to this link for the complete instructions.

 Get Help

If you are having issues with the hybrid, please "contact the YOUCANIC" team with any questions that you may have.

We can help you troubleshoot the problem FREE of charge as long as you send us the codes.  We need the codes from these four modules:

  • Engine ECU,
  • DC/DC converter,
  • BMS,
  • Power Electronics Module.

Once we have the codes, we can tell you if you have a bad power electronic module, hybrid battery, or both.

If your vehicle is at the dealership or mechanic, ask them for the list of codes and send them to us.    If you want to ship the car to Baltimore, we can repair it at a fraction of the dealer cost.  We love these cars and believe that it is a sin to pay over $10k to keep these cars running. 

Here is the proof. 

mercedes hybrid problems

 

Definition of Terms

  • CAN-BUS - Control Area Network. It serves as a channel of communication between various control modules.
  • DC- Direct Current (Energy from the battery measured in volts).
  • ECM   - Electronic Control Module (Main Control Module)
  • EMCM - Power Electronic Module or Electronic Motor Controller Module or Electric Motor ECU.
  • HV - High Voltage 
Mercedes Hybrid Vehicle No Start Problem The most common Mercedes-Benz hybrid problems that won't allow you to start the engine are caused by either a faulty power electronic module (part number 0009064703) or a defective hybrid battery.