Mercedes-Benz S400 hybrid vehicles are notorious for having hybrid issues that lead to no start condition.
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) eBay 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.
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 power electronic module should not be confused with the DC/DC converter. The power electronic module is mounted on the engine's side, on the passenger side, below the right exhaust manifold.
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. The S400 hybrid has no starter.
Replacing the Power Electronic Moule at a Mercedes-Benz dealership costs around $11,500.
The power electronic module runs around $6000, and labor is about $5500 at the dealership. These prices can vary slightly between Mercedes-Benz dealerships.
It is possible to buy a used or refurbished Power Electronic module on eBay at around $2000-$3000 and installed by an independent mechanic.
Typically an independent auto mechanic will charge an additional $2000 to $3000 to install it.
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.
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.
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 (0009064703), (eBay link).
The reason 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 need to read the Battery Management System module's fault codes. It is also important to run a full system scan to find out if there are 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
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:
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."
Sometimes the "converter" goes bad, and it can not transfer 160V AC to 12V DC or 12V AC to 160V AC, so the battery shows defective or vice versa.
Follow this guide to learn more about the Mercedes-Benz DC/DC converter and how to replace it.
Another problem with the S400 is the AC doesn't work. 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.
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 both our S400 Hybrids, and according to the service manager, the service was performed 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. In our S400, they had the "newer" version of the power electronic module, so they were not replaced. 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. Based on our research, the Power Electronic module on S400 Hybrid can fail anywhere 60,000 to 115,000 miles.
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 you are dealing with a high voltage (130 Volt) that can cause injuries and death if you do not take the required precautions.
Part Number (0009064703)
The following part numbers are often associated with the power electronic module.
Mercedes-Benz has issued a few different numbers for the power electronic module as the unit has gone over multiple revisions.
- 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