IsItAGoodCar
Reliability Guide

Common Problems with the
2018 Mitsubishi Outlander PHEV (GG)

We've identified 4 known issues that can affect the 2018 Mitsubishi Outlander PHEV (GG). 2 of these are serious faults that could be expensive to repair.

4
Known Issues
2
Serious
1
Moderate
1
Minor

All Known Issues

Battery Degradation & "BMU Reset" Masking

SeriousEngine

The traction battery naturally loses capacity over time. A major concern is the "BMU Reset" where a technician or seller resets the Battery Management Unit, forcing it to report 100% health (State of Health). This "masks" the actual degradation until the car relearns the true capacity over several weeks.

Est. Repair Cost: £3,000–£7,000 (Replacement)
Warning Signs:

Suddenly dropping range after a few weeks of ownership, Inconsistent EV range, Petrol engine starting even when battery shows charge

What to Inspect:
  • Use "PHEV Watchdog" and an OBDII dongle to check actual State of Health (SoH)
  • Check for a suspiciously high health percentage on high-mileage cars
  • Ask for a history of any BMU resets
Verified by IsItAGoodCar Research Team

AC Compressor Failure (Wrong Oil)

SeriousElectrics & Electronics

The electric compressor requires specialized POE oil. Using standard PAG oil during a regas will destroy the internal motor.

Est. Repair Cost: £1,000–£3,000
Warning Signs:

AC not cooling, Loud grinding noise when AC is on, EV system fault light

What to Inspect:
  • Verify that any AC service used POE oil specifically
  • Check AC operation in both EV and Petrol modes
Verified by IsItAGoodCar Research Team

Electric Heater Failure

ModerateInterior & Trim

The electric water heater (used when the engine is off) frequently fails. A small inline gauze filter can also block, preventing circulation.

Est. Repair Cost: £300–£1,000
Warning Signs:

No cabin heat when driving in EV mode, Heat only available when petrol engine is running

What to Inspect:
  • Test the heater while the car is in EV mode and parked
Verified by IsItAGoodCar Research Team

Rear Differential Mount Thud

MinorSuspension & Chassis

The rubber in the rear differential center mount perishes, leading to a "thud" or "clonk" when pulling away.

Est. Repair Cost: £150–£300
Warning Signs:

Thud from the rear when moving from a standstill, Clunk when releasing the brake

What to Inspect:
  • Inspect the rear diff mount bushing for cracks or play
Verified by IsItAGoodCar Research Team

Buying Tips for 2018 Mitsubishi Outlander PHEV (GG)

  • ✓Check for the "BMU (Battery Management Unit) Reset" scam, where sellers reset the battery health to show 100% capacity temporarily. A real test drive starting with a full battery is essential.
  • ✓Listen for a clicking noise from the rear motor on early models, which could indicate a mounting issue.
  • ✓Verify the operation of the rapid charging port (CHAdeMO) if you plan on using public chargers.
  • ✓Check the electric heater operation in EV mode; it's a common failure point that is expensive to fix.
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