The Opus IVS team recently supported a technician with an electrical fault on the W205 chassis

Opus IVS says its IVS 360 support, a unique offering in the automotive aftermarket developed by Opus IVS, offers live repair guidance worldwide to help workshops and technicians fix complex vehicles safely and fast.
Using the Drive Pro’s market-leading diagnostic software and extensive product knowledge, the IVS 360 team identifies the cause and steps needed to fix vehicle faults.
The IVS 360 team recently supported a customer with an electrical fault on a Mercedes-Benz W205. Following are the cause and steps they identified to fix the problem.

Affected vehicle: Mercedes C-Class 205 model series.

Reported issue: Using IVS 360 live support via the DrivePro, the customer reported that a warning message on the instrument cluster was displayed. The warning message displayed was an auxiliary battery malfunction message.

The Cause: A code read was performed and sent via the customer’s Opus IVS device, which revealed the following fault in the EIS ignition switch fault memory: “b21dc01 buffer battery of the Electronic Ignition Switch (EIS) malfunction there is a general electrical fault.”
IV6 360 experts explained that the most likely cause of the EIS fault code is that one of the power supplies to the EIS switch (ignition switch) is not present. It was suggested that the most likely possible cause of a general electrical fault would be the c8 capacitor shorting out internally.
The Opus IVS Technician also explained that the W205 does not have a separate auto start/stop battery, instead, it has a voltage dip limiter device (SEB) on the positive terminal of the battery under bonnet, and this works in conjunction with the c8 park pawl capacitor.
Therefore, the cause would most likely be because of no voltage to the ignition switch on the 30b circuit (Opus IVS explains this can be seen in EIS switch actual values on the DrivePro diagnostic tool).
The C8 Park Pawl capacitor would therefore need to be inspected and tested and replaced, as necessary.

Repairing the fault: The following steps were provided to the customer:
The C8 Park Pawl capacitor is in the front passenger side footwell area, so checks required included:

  1. At the c8 capacitor pin 2 = red 12v
  2. Pin 1 = earth brown
  3. Pin 3 = red/blue to EIS switch plug 1 pin 28, batt voltage

To remove the C8 Park Pawl capacitor, the following guidance was provided:

  1. remove the front passenger side kick panel trim.
  2. remove the glove box under the dash panel.
  3. remove the N/S/F section of the carpet.
  4. remove the plastic panel on the floor against the bulkhead.

The C8 Park Pawl capacitor is bolted to the left-hand side of the electrics panel, so instructions were provided to remove the 8mm nut and lift out the voltage converter. This feeds into the EIS (electronic ignition switch) at plug 1, pin 28 =30b voltage (this value can be seen in actual values)
It was noted that the voltage supply to the C8 Park Pawl capacitor comes from the rear SAM control unit in the boot from fuse 448.
Additional information: The IVS 360 team explained that if the c8 capacitor has shorted internally, then the 12v feed into the EIS at pin 28, additional battery voltage (terminal 30b), may still be missing even after replacing the capacitor and still can result in the same consumer battery message being displayed on the dashboard.
If the voltage converter has been replaced, and the fault and message remains, the following checks should be carried out:

  1. Check fuse 448 (Electrical fuse 448) in the K40/5 rear signal acquisition module.
  2. Check electrical lines, at the park pawl capacitor, for damage, repair, as necessary.
  3. Replace C8 (Park pawl capacitor).
  4. K40/5 rear fuse and relay module (in the boot/trunk on right)

IVS 360 support offers live repair guidance and remote programming services to help you fix complex vehicles safely and fast. All Opus IVS mechanical repair solutions come with live repair guidance from IVS 360 OEM brand-specific master technicians.

For more information, visit www.opusivs-au.com or contact 03 8561 7600 or sales-au@opusivs.com