‘Green’ Bullets: Tips for Servicing Hybrid Vehicles

‘Green’ Bullets: Tips for Servicing Hybrid Vehicles

Honda Insight hybrid maintenance
The Honda Insight oil pan

Newsflash: Hybrids are here to stay. The oldest Toyota Prius models are now 14 years old and many other hybrids from other manufacturers are crossing the 100,000-mile mark every day. Here are a few of my Silver Bullets, — or in this case “Green Bullets” — to help you maintain and service hybrids.


Toyota Prius and Camry hybrids have a 40 horsepower or more electric motor located between the engine and transmission, under the inverter. I’ve encountered two scenarios with these vehicles that both result from the same problem.

Scenario 1: The vehicle has no hybrid characteristics. In this state, the internal combustion engine is doing all the work, including regenerative braking. Scenario 2: With the internal combustion engine off, the vehicle will not go over 10 mph.

The most common pattern failure I’ve seen is the connections between the battery, inverter and motor. These are the orange cables that carry around 275 volts on the second-generation Toyota hybrids. These are secured with a bolt that can become loose over time, which results in a bad connection.

Ford escape hybrid components
Ford Escape (click to enlarge)

Honda Insight: Oil Pan

The 2000-‘06 Honda Insight has a magnesium oil pan. The threads on its drain plug hole are frail. Replacement plugs and gasket are available. Always use a torque wrench set to 29 ft.-lbs, and take the time to look for cracks, especially around the oil filter.

Ford Escape: Battery Filter

The Ford Escape hybrid has a special air filter for the battery pack’s cooling system. The air intake for the hybrid battery cooling system is located at the rear edge of the driver side cargo area side glass. Air for the battery is filtered by a serviceable filter located behind the driver side cargo trim panel. The normal service recommendation is to inspect and replace this filter as needed every 10,000 miles (16,000 km). The airflow from the Hybrid Vehicle (HV) battery exits under the vehicle, behind the bumper on the driver side.

Lexus: Rocking at Highway Speeds

Under certain circumstances, 2006-‘07 model year RX 400h owners may experience a back and forth “rocking” condition while maintaining the vehicle at a constant highway speed around 70 mph. The condition might feel like a worn suspension. However, Lexus has updated the HV ECU logic to help improve this condition.

Toyota Coolant Flow
Toyota Coolant Flow (Click to enlarge)

Toyota P1121: Replace the Coolant Flow Valve

The Toyota Prius has complex cooling systems to make sure the battery, electric motor and engine run at optimal temperatures. This is done primarily with the coolant flow valve. A P1121 code means the valve should be replaced.

The ECM monitors the position of the valve based on the valve position signal from the water valve position sensor (potentiometer), which is connected to the valve. The ECM determines the position of the valve according to the voltage of the respective step.

The ECM checks for malfunctions by monitoring the various temperature sensors. If the valve changes position and no changes or slow changes in temperature occur, it will set the P1121 code. The only way to resolve this problem is to replace the coolant flow valve and flush the system.

This system of sensors can also detect if the coolant heat storage tank is no longer ­functioning.

Hybrid Weight Oils

Some late-model hybrids call for 0W-20 or 5W-20 weight motor oil. Not using the correct weight will damage the top-end of the motor, but the most likely outcome is a code will set for the variable valve timing system. Without the correct oil weight, actuation of the solenoid and servo that controls camshaft timing will be off and detected by the camshaft position sensor. This can even occur if a Toyota Prius is filled with 5W-30 oil.

You May Also Like

Voltage Drop Testing

The measurement of voltage is like the speed of the traffic.

Picture your local freeway. When the traffic is light, the traffic flows at the same speeds, even if there is a lane closure. As the number of cars increases for rush hour, the speeds slow down. A lane closure can cause traffic to come to a standstill. 

In this example, the cars during rush hour are like load and power in a starter motor on a circuit. The lane closure is like a bad connection or damaged wire. With light traffic loads, the speed of the traffic will not slow down as lanes merge. But, during rush hour, the speeds drop and the backup builds. In an electrical circuit, the resistance produces heat.

Spark Plug Fouling

Understanding why spark plugs get dirty.

Why Alternators Are Subject To Ripple Voltage

The alternator produces an AC current that must be converted into DC current by way of a rectifier.

Understanding Stop/Start Charging and Starting Systems

The problem may not have been caused by a complicated reason, something simple may have caused the system not to work.

Remanufacturing And The EV-Battery Challenge

One researcher is particularly interested in the fate of EV batteries once they reach the end of their automotive lifecycle.

Other Posts

Chassis Control Modules After Reconnecting Battery

To resolve the issue, fully disconnect the negative lead from the battery terminal.

New Oil Specifications

Many 0W16 oils have a new donut certification mark on the bottle called API SN-PLUS and SN-PLUS Resource Conserving.

Alternator Testing For No Charge Conditions

Many alternator problems turn out to be nothing more than a bad connection at the alternator or a bad wiring harness.

Replacing Strut Mounts on 2013-2018 Toyota RAV 4s

Follow along to learn how to replace upper strut mounts on 2013-2018, and newer, Toyota RAV 4s. Sponsored by PRT.