Practical hybrid service tips

Jan. 1, 2020
The following hybrid maintenance items are easily completed, but you must follow the proper procedures to avoid unhappy customers and vehicle damage.

Hybrid vehicles are here to stay; almost every vehicle manufacturer announces additional hybrid vehicles each year. Why is this happening? The National Highway Traffic Safety Administration (NHTSA) sets Corporate Average Fuel Economy (CAFE) regulations as directed by the president of the United States. The CAFE standard for automobiles is set to just over 35 mpg by the year 2016 and then to just over 54 mpg by 2025. Currently there is no other technology that can meet or exceed these requirements, so expect to see a lot more hybrids in your future service work.

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The most numerous hybrids on the road today are made by Toyota followed by Honda. There are also many Fords, General Motors, and others in smaller numbers. Regardless of the brand, there are many common maintenance items for all of them.

The following hybrid maintenance items are easily completed, but you must follow the proper procedures to avoid unhappy customers and vehicle damage.

Lube, Oil and Filter Service
One of the most difficult things to get used to when driving a hybrid vehicle is the idle stop mode. Many hybrids shut off their internal combustion engine (ICE) when the car comes to a stop. Further, most hybrids can propel themselves on battery power at low speeds. When you pull a hybrid vehicle into your shop for service work, don’t forget to turn off the power to the vehicle. Some vehicles use a power button while others still use a traditional key. Make sure the “READY” light on the instrument panel is off.

You might think that turning off the vehicle power would be a no-brainer, but the car is so quiet in the idle stop mode that it is easy to forget to turn off the power. I have owned hybrid vehicles for the past six years, and I still forget to shut off the vehicle power at times when I park my car. If you forget to turn off the power, the engine can start on its own without warning while you are performing service work.

If you have just drained the engine’s oil and removed the filter, it can cause quite a mess and also cause engine damage. Some hybrids have a hood switch that prevents the engine from starting when the hood is opened. If the engine starts when you opened the hood, you need to shut off the vehicle power switch or the key switch. On vehicles using “smart” keys, it’s best to store the key well away from the car while performing routine service.

After changing the engine oil, you will need to start the engine to make sure the oil filter does not leak. Check your service information system for the proper procedure. Most hybrids do not start the engine when you turn on the vehicle power again. To force the engine to start on some models, turn the heater control to full hot or full cold. If you have a factory scan (or capable aftermarket) tool, you can enter the inspection and maintenance mode and force the engine to run continuously. Don’t forget to reset the engine oil life indicator.

Most hybrids and newer cars have undercar engine covers and body covers to improve aerodynamics; be sure you return these covers to their original positions with all the fasteners and bolts. I have seen several vehicles with their under-engine covers dragging on the ground as the vehicle is driven down the road. These situations could have been the result of recent service work where the fasteners were not installed properly or even at all. Obviously this can result in a very unhappy customer.

Transmission/Transaxle Fluid
Most hybrids utilize a special transmission or transaxle that may use a special transmission fluid type and fluid level check procedure. Some do not use a dipstick; some of the fluid level check procedures require the use of a scan tool to monitor fluid temperature or to activate a fluid pump.

My point? If you are going to tell a customer that you checked their transmission fluid level, make sure you check it properly. I recommend that you do not check the transmission fluid and let the customer know that you did not check it unless you have the tools, training, and equipment to do so.

Tire Pressure and Tires All hybrids rely on proper tire inflation to obtain maximum fuel economy. Many hybrids have a tire pressure display on the instrument panel. When performing maintenance on a customer’s vehicle, it is a good practice to insure the tire pressures are set to the specifications on the door pillar.

Many hybrid vehicles utilize low rolling resistance tires. Low rolling resistance tires are usually a little more expensive than regular tires, but they do offer better fuel economy. When a customer needs replacement tires for their hybrid vehicle, be sure to determine if the vehicle’s original tires were low rolling resistance tires. Today’s low rolling resistance tires can improve fuel economy by as much as 4 percent. Installing regular tires on a Toyota Prius that normally would get 50 mpg could result in a two-mpg decrease. Hybrid vehicle owners would not be happy with the decrease in fuel economy, especially with today’s fuel prices. Make sure your customers know all the options, advantages and disadvantages of each tire type.

Accessory Drive Belts Some hybrid vehicles utilize accessory drive belt(s) for the water pump, air conditioning compressor, etc. There is a General Motors hybrid system called the Belt-Alternator-Starter (BAS) system, later models have been renamed to the eAssist system. These systems utilize a wide 7-rib accessory belt to couple the hybrid motor/generator to the engine’s crankshaft. These systems use a very strong belt tensioner system that requires a special spring compressor tool to change the accessory belt.

Some hybrids do not utilize any accessory drive belts for power steering, air conditioning, water pump, etc.; everything is electric motor driven instead. These beltless systems still utilize a crankshaft harmonic damper that may have belt grooves but no belt. Keep in mind, too, that these electric drives are often high voltage systems that require care when servicing.

Cooling Systems Service A hybrid vehicle can have as many as three different liquid cooling systems. As of this date, all of them use the same coolant (antifreeze) as the engine in the vehicle, but have a totally separate cooling system with its own coolant reservoir, water pumps, hoses, fans, and radiator cap. The vehicle’s radiator can have up to three different sections, all in the same radiator assembly, that are related to the hybrid cooling system. These systems can all be serviced and you can replace the coolant as long as you follow the proper service procedures to insure that the system has had all the air purged.

What are the three separate cooling systems?

1. Engine:  Obviously the internal combustion engine (ICE) has cooling needs, but on a hybrid vehicle, as well as non-hybrids, the ICE has heating needs too. The faster the engine can reach full operating temperature, the faster it can enter the electric motor only mode and the idle stop
mode which results in better fuel economy. Many Toyota hybrids utilize a heat exchanger in the exhaust system to help heat the engine coolant upon startup. There are actually two coolant hoses that attach to the exhaust system. There is a temperature sensitive valve that closes and blocks the coolant flow once the engine reached normal operating temperature.

2. High voltage electronics, controllers, converters, and inverters: All hybrids have some high voltage electronics, controllers, converters, inverters, batteries, etc. that need to be cooled or heated. Many hybrids use a separate liquid cooling system to control the temperature of the under-hood hybrid electronics and have an air cooled/heated battery. Other hybrids use climate-controlled air in the passenger compartment to perform the cooling and heating of the hybrid electronics as required. These vehicles utilize some type of inlet vent to pull in the air and run it over the hybrid electronics and/or battery to control their temperature. Make sure these inlet vents are not blocked with the customer’s own personal property such as pillows, blankets, coats, pets, etc. If the inlet vents are blocked, the hybrid high voltage electrical system can overheat resulting in poor performance, warning lights in the instrument panel, and even damage to the hybrid system.

3. High voltage battery:  Some vehicles use liquid to cool/heat the battery too. As a general rule, air cooled components are typically in the passenger compartment and liquid components are typically under the hood area, but there are always exceptions.

Brake Service
Most hybrid vehicles will not need a set of new brake pads for more than 100,000 miles or more. These vehicles utilize a regenerative brake system to help slow the vehicle when possible and then blend the hydraulic brake system as needed to achieve the desired deceleration rate. All of my hybrid vehicles have brake pads that look like they have not worn at all, even after 70,000 miles.

If you find a hybrid vehicle that needs brake service, there are several precautions to take to prevent damage to the brake system, the hybrid system, and to yourself.

1. Most hybrid vehicle brake systems utilize a brake pedal feel simulator. This means that the brake pedal does not actually apply the hydraulic brakes under most circumstances, instead it is simply an input parameter to the hybrid brake controller requesting that the vehicle be slowed down or stopped. The amount of regenerative braking vs. hydraulic braking is determined by the brake pedal position, change in pedal position, vehicle speed, battery state of charge, etc.

2. Because these hydraulic brake systems are computer controlled, changing brake pads, calipers, rotors, etc. can be dangerous if you do not follow the proper service procedures. The big problem is that the brake system can become pressurized without warning as part of a self-test that the hybrid vehicle runs at times. Sometimes all it takes to trigger a self-test is opening the driver’s door.  Always review the procedures outlined in the service information system BEFORE beginning your repairs.

3. If you have had to open the hydraulic system to replace a caliper, wheel cylinder, etc. be sure to use the proper brake fluid and the proper bleeding procedure. Many hybrid vehicles utilize a scan tool based bleeding procedure to help purge the air from the brake system’s accumulators, motors, pipes, etc. If you can avoid running the master cylinder reservoir empty during your brake service, you should be able to just bleed the brakes normally.

12-Volt Battery
All hybrid vehicles have a regular 12-volt electrical system for the majority of vehicle systems. If you have a hybrid vehicle with a dead 12V battery, you should be aware of a few things before attempting to charge or jump-start the 12V battery:

1. Most Toyota Prius vehicles use an Absorbent Glass Matt (AGM) battery. There batteries should not be fast charged, most of the batteries could be damaged if the charge current is over 4.2 amps or if the charge time is longer than 10 hours. Use a jumper box to jump-start (power up) a Prius, not a fast charger.

2. Many hybrid vehicles have their 12V battery stored in the trunk area. The trunk area may not accessible with a dead battery since the trunk only opens with an electric solenoid. These vehicles have a jump start terminal under the hood to allow you to power up the vehicle, but it is not to be used to jump start other cars. Keep in mind that the engine does not have to start when the vehicle is powered up. As long as the “READY” light is on, the 12V battery should be receiving a charge from the hybrid system.

3. Hybrid vehicles with the 12V battery under the hood can be jump-started (powered up) the same way any other vehicle is jump-started. Do not use a hybrid vehicle to jump-start another vehicle; the chance of very expensive hybrid system damage is very high.

12-Volt Charging System
Hybrid vehicles do not use traditional alternators to charge the 12-Volt battery; instead they use a DC-to-DC converter to use the high voltage (100V to 360V) hybrid DC battery to charge the 12-Volt DC battery.

If you have a hybrid vehicle with a repeat dead 12-Volt battery, you should check the charging system. When checking the charging system of a hybrid vehicle you must power up the vehicle and make sure the “READY” light is on (the engine does not have to be running). Make sure there are no warning lights on or trouble codes set. Place a digital multimeter across the battery terminals; the terminal voltage should be close to 14V. If it is not, the hybrid DC-to-DC converter system may not be working properly and will need to be diagnosed.  

Most Toyota DC-to-DC converters are not serviced separately from the under hood inverter/converter assembly. This assembly is very expensive and difficult to change. Make sure you follow the proper high voltage service procedures and use the proper personal protective equipment (PPE).

Honda DC-to-DC converters are serviced separately and are located behind the back seat. The Honda diagnostics are easy to follow and the part is easy to access, make sure you follow the proper high voltage service procedures and use the proper personal protective equipment (PPE).

Ford and GM DC-to-DC converters vary in location and serviceability.

Starting Systems
Some hybrids use both a traditional 12V starter motor and a separate high voltage (HV) high-speed starter motor/generator system. The 12V starter motor starts the engine initially and then the separate high voltage high-speed starter motor/generator starts the engine for the remainder of the ignition power cycle and is used as part of the idle stop system.

All Toyota hybrids and some Ford hybrids do not utilize a traditional starter motor; instead they use a large motor/generator to start the vehicle using the high voltage battery. If you have a Toyota or Ford hybrid vehicle that will not start, you probably have a high voltage hybrid system problem that will require a trained technician with the proper safety equipment and tools to diagnose. A dead high voltage battery could also cause this. These high voltage batteries should not ever go dead as long as the hybrid system is operating properly; however, a customer who runs out of gasoline and then continues to drive on electric power will cause the battery to run low enough that it may not allow the hybrid system to start the engine again.

High voltage batteries range from 201.6V to 288V and cannot be charged with a typical battery charger. Sometimes you can just let the vehicle warm up in the shop or outside on a warm day and the battery may recover enough to start the engine again. If you can get the engine to start, the hybrid system will use the engine to charge the high voltage battery. If you cannot get the engine to start, a dealership has access to a very expensive high voltage charger or charging procedure to get the engine running again.
Conclusion Hybrid vehicles are here to stay. Electric vehicles are also here too. With the millions of these types of vehicles on the road today, it would be smart to educate yourself, purchase the tools, and start performing the service work on hybrids. You could bring in a whole new customer base! 

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