Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Testing
Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High Voltage Disabling procedure includes the following steps:
- Identify how to disable high voltage.
- Identify how to test for the presence of high voltage.
- Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Before working on any high voltage system, be sure to wear the following Personal Protection Equipment:
- Safety glasses with appropriate side shields when within 15 meters (50 feet) of the vehicle, either indoors or outdoors.
- Certified and up-to-date Class "0" Insulation gloves rated at 1000V with leather protectors.
- Visually and functionally inspect the gloves before use.
- Wear the Insulation gloves with leather protectors at all times when working with the high voltage battery assembly, whether the system is energized or not.
Failure to follow the procedures may result in serious injury or death.
- Disable the high voltage for every high voltage component. High Voltage Disabling .
- With high voltage disabled, identify the A4 Hybrid/Electric Vehicle Battery Pack high voltage connector X3 and disconnect; if the X3 connector has not already been disconnected. High Voltage Disabling .
- Identify A28B Hybrid/Electric Vehicle Battery Charging Disconnect Module Relay high voltage connector X1 and K57B Battery Charger Control Module 2 high voltage connector X2, and disconnect both if not already disconnected.
- Test the high voltage cable for an open condition.
- If infinite resistance
Battery Positive and Negative Cable - Replace
- Go to next step: If less than infinite resistance
Go to next step: T18B Battery Charger 2 - Replace
- If infinite resistance
- Enable high voltage and test for DTCs. High Voltage Enabling
- Verify DTC P0D26 is not set
- If DTC P0D26 is set
A28B Hybrid/Electric Vehicle Battery Charging Disconnect Module Relay - Replace
- Go to next step: If DTC P0D26 is not set
- If DTC P0D26 is set
- All OK.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.