Tech Tip: Mercedes GLC350e High Voltage System Warning Message in Cluster

Oct. 11, 2024

A customer brought in their Mercedes GLC350e with an intermittent high voltage warning message.

Related To: ALLDATA

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A customer brought their Mercedes GLC350e into the shop with an intermittent high voltage warning message on in the instrument cluster. When the warning message is present, the vehicle stops but it will restart after waiting a while.

Case details

After connecting a scan tool, the technician retrieved the following diagnostic trouble codes (DTCs):

P1CF5 00 - An insulation warning in the hybrid high voltage onboard electrical system
P1426 00 - A vehicle side insulation fault in the hybrid high voltage onboard electrical system
P0AA6 00 - An insulation warning in the hybrid high voltage onboard electrical system
P142A 00 - A vehicle side insulation alert in the hybrid high voltage onboard electrical system

The technician checked the insulation of all the high voltage components and found the positive temperature coefficient (PTC) heater had 1500 ohms to ground.

Confirmed repair

He replaced the PTC heater, cleared the DTCs and road-tested the vehicle. There were no further issues. Problem solved!

About the Author

ALLDATA Tech-Assist Team

The ALLDATA Tech-Assist Diagnostic team is a group of top-notch ASE Master Technicians who have devoted numerous years to the automotive industry as independent shop and dealership technicians, shop owners and a many of them have also been automotive instructors.

Each team member is passionate about helping technicians of all skill levels get vehicles diagnosed and repaired quickly and correctly the first time. Because they help diagnose such a large number of vehicles every day, they are a wealth of experience-based diagnostic knowledge.