On the 2016 Mitsubishi Outlander PHEV, B1115 indicates a malfunction in the electric water pump used for battery pack or cabin heater thermal management -- this is a PHEV-specific code that does not appear on the ICE-only Outlander.
What B1115 means
The 2016 Mitsubishi Outlander PHEV (ZK/ZL platform) uses multiple electric water pumps to manage heat for both the 12 kWh traction battery pack and the cabin heater circuit, which supplements or replaces the engine's waste-heat heater when running in EV mode. Code B1115 is stored by the EV-ECU or the HVAC control unit when a fault is detected in the electric water pump circuit -- typically a pump that has stopped responding to drive commands, drawn excessive current, or lost feedback from its speed sensor. Because the pump is essential for battery thermal protection in hot weather and for cabin heating in cold climates, the system limits EV performance when B1115 is present.
Symptoms
- EV system warning light or 'Service EV System' message on the instrument cluster
- Reduced EV range or battery charging limited in hot ambient temperatures (thermal protection mode active)
- Cabin heater produces reduced or no heat in full-EV mode even with heater set to maximum
- B1115 stored in the PHEV EV-ECU or HVAC module -- requires a PHEV-capable scan tool to read
- Possible 12 V battery drain if the pump relay is stuck on
Common causes
- Failed electric water pump motor -- brushless pumps can develop open-circuit motor windings, especially after 60,000-80,000 km on third-generation PHEV units
- Blocked pump impeller due to coolant debris or a collapsed coolant hose reducing pump output below the speed sensor threshold
- Damaged pump wiring or corroded connector at the pump's harness connector
- Pump drive relay failure causing the pump to receive no power
- Failed pump speed/feedback sensor making a functional pump appear unresponsive to the control module
Diagnostic approach
- Identify which electric water pump circuit is implicated using a PHEV-capable scan tool — The Outlander PHEV has more than one electric pump circuit. A scan tool capable of reading PHEV modules (Mitsubishi MUT-III or equivalent) will identify whether B1115 relates to the battery cooling pump or the cabin heater pump. Note freeze frame data -- pump speed, coolant temperature, and ambient temperature at fault time.
- Check for voltage at the pump connector with the circuit commanded on — With the fault active and the relevant pump commanded on via the scan tool's actuator test, measure voltage at the pump connector. The pump should receive 12 V at its supply pin. No voltage indicates a failed relay or open wiring; full voltage with no pump movement confirms a motor failure inside the pump assembly.
- Inspect the coolant circuit for blockages and the pump for physical damage — Drain the affected coolant circuit (battery cooling is separate from the engine cooling circuit on the PHEV) and inspect the pump inlet for debris or hose collapse. On Outlander PHEV units, the Mitsubishi-specific pink coolant must be used -- standard blue or green coolant causes seal swelling that can jam the pump impeller.
Make & model notes
Mitsubishi: The Outlander PHEV uses Mitsubishi-specific pink coolant (part number MZ320189 or regional equivalent) in the battery and heater electric pump circuits. Using standard green or blue OAT coolant in these circuits will cause the electric pump seals to swell and can trigger B1115 within months of a coolant service.
Mitsubishi: B1115 is a PHEV platform-specific code -- it does not appear on the 2016 Outlander with the 2.4L petrol or 2.2L diesel engine only. If a non-PHEV Outlander shows this code it indicates a diagnostic error or incorrect VIN selection in the scan tool.
FAQ
Can I drive my 2016 Mitsubishi Outlander PHEV with B1115 active?
The vehicle will drive, but in battery thermal protection mode. EV range will be curtailed and the battery may not charge fully to prevent thermal damage without active cooling. In very hot weather, continued driving without repairing the pump can shorten battery life. Repair promptly in summer.
Is B1115 on the Mitsubishi Outlander PHEV covered under the EV battery warranty?
Mitsubishi's EV battery warranty varies by market, but the electric water pump itself is typically a mechanical component rather than a battery warranty item. Some markets have extended drivetrain warranties that cover pump failures -- check with your Mitsubishi dealer using your VIN.
What coolant should I use when replacing the electric water pump on an Outlander PHEV?
Mitsubishi specifies their own pink EV coolant (MZ320189 or regional equivalent) for the battery and heater circuits. Do not use conventional green, blue, or red OAT coolant -- these are chemically incompatible with the pump seals and heat exchanger coatings used in the PHEV thermal management system.