Isolation Fault Diagnostics & Repairs
Specialist high-voltage diagnostics to pinpoint insulation leaks and deliver repair-first solutions that get EVs and hybrids back to charging, starting, and “ready” mode.
Understanding HV Isolation Faults
An isolation fault indicates reduced insulation resistance between the high-voltage (HV) system and the vehicle body. Modern EVs and hybrids monitor insulation continuously; when readings fall outside specification, the vehicle can disable the HV system to protect occupants and components.
Isolation faults can be caused by issues inside the HV battery pack (for example, module leakage, water ingress, corrosion, or internal component faults) or elsewhere on the HV system (cabling, heaters, inverters, chargers, etc.). Our process focuses on finding the exact leakage point, confirming the root cause, and validating the repair.
Selection of Covered Vehicles - Isolation Fault Diagnostics & Repairs
View a selection of vehicles that have Isolation Fault diagnostics & repair solutions
Audi
- Audi E-Tron 2014-present
Fiat
- Fiat 500e 2020–present
Hyundai
- Hyundai Ioniq (2016–2022)
Jaguar
- Jaguar I‑PACE 2018-2024
Kia
- Kia EV6 2021-present
Mini
- Mini (all BEV) 2021-present
Nissan
- Nissan Leaf (Gen 1) 2013-2018
Nissan Leaf (Gen 2) 2017-present
Polestar
- Polestar 2 2020-present
Porsche
- Porsche Taycan 2022-2024
Seat / Cupra
- Seat/Cupra (all BEV) 2021-2024
Škoda
- Škoda (all BEV) 2021-2024
Smart
- Smart Fortwo 2017-2024
Tesla
- Tesla Model S (2012–present)
- Tesla Model X (2015–present)
- Tesla Model Y (2019–present)
- Tesla Model 3 (2017–present)
Volkswagen
- Volkswagen ID3 2021-2024
- Volkswagen ID4 2021-2024
- Volkswagen ID5 2021-2024
Can't find your vehicle?
The vehicles listed are a selection of Isolation Fault Diagnostics & Repairs. Please contact us if your vehicle is not listed.
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Case Studies
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Common Symptoms
EV / hybrid warning messages
Electrical system malfunction, EV system warning, or HV warning lights may appear.
Vehicle won’t start or enter “ready” mode
The vehicle may refuse to power up after shutdown, or display “no restart”.
Charging issues
The vehicle may be unable to charge, stop charging unexpectedly, or inhibit charging completely.
Reduced drive capability or shutdown
Some vehicles will reduce power or shut down the HV system when insulation readings are out of range.
Vehicles Affected
- High-voltage battery packs (module leakage, internal faults)
- High-voltage contactor / switching modules (example: VAG SX6 contactor module on Audi e-tron cases)
- Water ingress-related insulation failures (e.g., drainage issues leading to HV battery contamination)
- HV cabling and connected HV components (vehicle-specific)
What's Included?
Specialist diagnostic assessment
We start with a structured diagnostic approach to confirm the isolation fault, capture relevant fault codes, and determine whether the issue is likely inside the battery pack or elsewhere on the HV system.
Insulation / leakage testing to pinpoint the fault
We carry out systematic testing to locate the leakage point (for example, isolating circuits and measuring insulation resistance) rather than guessing and replacing parts.
Targeted repair-first rectification
Where appropriate, repairs may include module-level battery work, component replacement (e.g., contactor module faults), drying/cleaning and corrosion rectification following water ingress, and resealing/rectification work to prevent recurrence.
Verification and final system checks
We complete post-repair verification to confirm insulation readings are stable, clear fault memory where applicable, and confirm correct vehicle operation (ready mode, charging, and road-test validation where relevant).
All work is backed by a 12-month warranty covering both parts and labour, giving you peace of mind and confidence in the quality of our service.
Very helpful at solving a major fault. Though a big job, itc cost half of what it would have done at main dealer who would have replaced more than needed. Customer service very good.