A pre-purchase inspection (PPI) for a used plug-in hybrid (PHEV) should include everything checked on a conventional used car, plus a thorough evaluation of the high-voltage battery, charging system, and hybrid components. Ideally, the inspection is performed by a technician familiar with that specific make and model.
Here's what a comprehensive inspection should cover:
1. High-voltage battery (most important)
Ask the inspector to evaluate:
- Battery state of health (SOH), if available through manufacturer diagnostics.
- Signs of abnormal battery degradation.
- Whether any battery-related fault codes are stored.
- Cell voltage balance (if supported by diagnostic tools).
- Battery cooling system operation (fans, pumps, filters, coolant where applicable).
Questions to ask:
- Has the battery ever been replaced under warranty?
- Is any battery warranty still transferable?
2. Charging system
The inspector should verify:
- The charging port is undamaged and locks properly.
- AC charging functions correctly.
- The charging cable (if included) works properly.
- No corrosion or overheating around charging components.
- Charge door and seals are intact.
3. Hybrid drivetrain
Inspect:
- Electric motor(s)
- Inverter/converter
- DC-DC converter
- Hybrid transmission or eCVT
- High-voltage wiring and connectors (for damage—not by opening sealed components)
- Cooling systems for hybrid electronics
4. Internal combustion engine
Because PHEVs may spend long periods running mostly on electricity, check:
- Oil condition and maintenance history
- Coolant condition
- Belts and hoses
- Leaks
- Engine starts smoothly after sitting
- No excessive smoke
- Proper operation after warming up
5. Diagnostic scan
A full scan should include:
- Engine control module
- Hybrid control module
- Battery management system
- ABS
- Airbags
- Transmission
- Body control module
Look for:
- Current codes
- Pending codes
- Recently cleared codes
- Freeze-frame data if available
6. Test drive
Drive in both EV and hybrid modes:
- Smooth transitions between electric and gasoline power
- Regenerative braking feels consistent
- No unusual noises from motors or transmission
- Strong acceleration
- Steering and suspension feel normal
- Verify expected EV range if the battery is adequately charged
7. Conventional used-car inspection
Don't skip the basics:
- Brakes (including rotor corrosion from infrequent use)
- Tires (matching set, tread depth, uneven wear)
- Suspension
- Steering
- Wheel bearings
- Exhaust
- Cooling system
- Undercarriage rust
- Fluid leaks
- Lights
- HVAC
8. 12-volt battery
Many hybrid issues begin with a weak auxiliary battery.
Check:
- Age
- Voltage
- Load test results
9. Service history
Look for:
- Regular maintenance
- Software updates
- Recall completion
- Accident repairs
- Battery-related repairs
- Cooling system maintenance
10. Software and recalls
Confirm:
- All recalls have been completed.
- Hybrid and battery management software is up to date, if applicable.
Red flags
Consider walking away if you find:
- Battery warning lights
- Large difference between indicated and expected EV range (after accounting for weather and driving conditions)
- Numerous hybrid fault codes
- Evidence of water intrusion
- High-voltage system repairs with poor documentation
- Salvage or flood history
- Charging system that doesn't function correctly
Questions to ask the seller
- How often was it charged?
- Was it stored for long periods with a full or empty battery?
- Has the battery ever been repaired or replaced?
- Has it always been serviced according to the manufacturer's schedule?
- Does it come with both charging cables and any charging adapters that were originally included?
If you're paying for a professional inspection
Ask the shop specifically whether they can perform:
- Manufacturer-specific hybrid diagnostics
- High-voltage battery health assessment
- Battery state-of-health or capacity testing
- Charging system verification
- Full electronic scan of all vehicle modules
Many general repair shops can inspect the mechanical aspects of a PHEV, but a dealer or an independent shop that specializes in hybrids often has access to manufacturer diagnostic tools that can provide a more complete assessment of the battery and hybrid system.
If you tell me the year, make, model, and approximate mileage of the PHEV you're considering, I can point out the model-specific items that deserve extra attention during the inspection.
