Mercedes-Benz Hybrid High Voltage Battery =Resistance Check

In this short guide, we show how to check the resistance of the high voltage battery. This post is for information purposes only, and these steps should only be performed by trained technicians. When performing this procedure, make sure to wear appropriate gloves. 

1. Disable the high voltage system using a professional bi-directional scanner such as Star Diagsnotic or Autel MaxiCOM. 
2. Disconnect the 12-volt battery in the trunk. 
3. Open the hood and locate the hybrid high voltage battery on the passenger side. On some Mercedes-Benz models, the hybrid battery may be in the trunk.
4. Unplug the electrical connector from the high voltage battery. 
5. Loosen the 10mm bolt and disconnect the orange cable connecting the A/C and power electronic module. 
6. Pull the black ring up on the orange cable from the DC/DC converter, then pull out the cable. 
7. Set a digital multimeter to measure current. The reading should be under 2 ohms.  
8. Measure the resistance between the two terminals shown in the picture. 

If the resistance is below two ohms, the battery is ok. 

If the resistance is above two ohms, the battery is not good and needs to be replaced. 

Keep in mind that even if the battery shows under two ohms, it may still not charge and be faulty due to internal failure.  

This test was performed on a 2010 Mercedes-Benz S400 hybrid. 

 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.