Are you ready for hybrids?

Aug. 17, 2011
Have you thought about performing diagnostic service and repairs on light-duty hybrid electric vehicles (HEVs)? If not, you might consider getting into the business, because growing acceptance of hybrids by the U.S. motoring public means growing service opportunities for technicians.

Editor’s note: Author Bob Rodriguez dives into the subject of light-duty hybrid-electric vehicle service and repair by discussing what hybrids are, what kinds are out there, how they are classified, and how to prepare to fix them. In a follow-up article, Bob will further discuss various types of hybrid-electric vehicles, their frequency and criticality of repairs, and where to find hybrid vehicle training.

Have you thought about performing diagnostic service and repairs on light-duty hybrid electric vehicles (HEVs)? If not, you might consider getting into the business, because growing acceptance of hybrids by the U.S. motoring public means growing service opportunities for technicians. Some of the many light-duty hybrids registered in the U.S. are past warranty, and both dealer and aftermarket technicians are increasingly being asked to service them. So the question is: Are you ready for hybrids?

Of course, if you’re going to work on hybrid-electric vehicles, you need to know something about them. In a nutshell, a hybrid is a vehicle that uses two or more sources of power. The concept is anything but new, going as far back as 1900 when Ferdinand Porsche developed the “Lohner-Porsche Mixte Hybrid,” the first gasoline-electric hybrid automobile in the world1.But not until a decade or so ago (1999) have light-duty hybrids been a part of the U.S. landscape. Hybrid vehicle sales have taken off ever since. Even when overall U.S. vehicle sales dropped by 3% in 2007, hybrid vehicle registrations rose by 38% to over 350,000 vehicles. In fact, the United States is the largest hybrid market in the world, with roughly 2 million hybrid automobiles and SUVs sold as of May of this year (2011).2 Reportedly, as of 2007 about 26% of U.S. hybrids are registered in California. Other hybrid hot spots include Florida, New York, Texas, Washington, Illinois, Virginia; Pennsylvania, Massachusetts and New Jersey. 3

Growing service opportunities

In 1999, Honda introduced hybrid vehicles to the U.S. market with their first generation Insight. Toyota quickly followed with their second generation U.S. model Prius. In 2003 Honda’s Civic Hybrid became the third hybrid sold here, and in 2004 the Ford Escape SUV became the first domestic hybrid to be offered, followed by its sister, the Mercury Mariner SUV.

Other HEV makes and models have since come in quick succession, including those from Audi, BMW, Cadillac, Chevrolet, Dodge, Lexus, Mercedes Benz, Nissan, Toyota and even Porsche! Several hybrid models have been offered and then been discontinued, including the hybrid Dodge Aspen and Durango, and the hybrid Honda Accord.

Looking ahead, OEMs planning to introduce a hybrid for the first time to the U.S. include Hyundai, Lincoln, Subaru, Volkswagen and more. With projections of ever-increasing HEV market penetration, finding opportunities to service hybrid vehicles should be a no-brainer.

At first hybrids were intended to boost fuel economy, but the on-demand torque delivered by electric motors soon made the OEM’s main reason for “hybridizing” vehicles that of enhanced driving performance.

Indeed, many OEMs seem to be obsessed with offering high-performance hybrids, with only modest fuel economy gains over their ICE (internal combustion engine) counterparts.

Hybrids have gone upscale too, with a wide variety of accessory options, infotainment systems, and cabin creature-comfort features. Toyota even offers a solar roof to help cool a parked vehicle on hot sunny days.

Hybrid drives

If you consider diesel-electric submarines or diesel-electric locomotives, you’ll realize that the hybrid drive concept is anything but new.

Light- and medium-duty hybrids now come in a variety of configurations. Power from the internal combustion engine (running on natural gas, diesel, propane or gasoline), combines with auxiliary back-up or primary power from electric batteries, ultra/super capacitors, hydraulic-pneumatic accumulators, or even super-high rpm flywheels. Other power options like micro-turbines are used in non-road special-purpose hybrids. U.S. light-duty hybrids are almost exclusively gasoline-electric.

For virtually all these hybrids (except the Chevrolet Volt), motive power is transferred to the wheels in either a parallel or series/parallel drive configuration (see schematics). A variety of transmissions, clutches, and other features are used depending on the desired amount of performance (or alternatively, fuel economy), and selling price.

Some hybrids come with manual or automatic (up to 8 speed) planetary gearset transmissions; others come with continuously-variable (CVT) transmissions (some with sporty “paddle” type shifters). See our list of commonly used hybrid drive systems.

High-voltage (HV) controls vary also, along with the types of batteries and capacities, type of battery cooling, and so on. There may be one, two, or more high-voltage (HV) “electric machines” (drive motor/generators) used. These may be three-phase AC permanent magnet (PM) or inductive motors. You’ll want to know and understand these variations when (or if) deciding to service these vehicles.


Types of hybrids

Hybrids are “classified” by body style and by the degree of performance and luxury they offer. But technically speaking, they are also classified by how far they can be driven on batteries alone.

For example, a so-called “full hybrid” can cruise a limited distance without the engine running. A “partial hybrid,” on the other hand, runs on ICE power at all times expect when stopped. All use fuel saving features like regenerative coasting/braking; most use variable valve timing and stop/start (engine shut-off) strategies; some use cylinder displacement-on-demand (DOD); some use Atkinson Cycle (five-cycle) or Miller cycle (five-cycle with low rpm boost) engines and/or similarly interesting innovations4.

You should know that the vast majority — perhaps 90% — of U.S. registered HEVs are “full hybrids,” using the Type 1 drive system, as described in the sidebar to the right.

Service opportunities

While hybrids have proven to be amazingly reliable, they do have their quirks. For example, Toyotas located in the northeastern U.S. have reportedly suffered corroded brake parts from a combination of salted roads and brake system under use — regenerative braking systems do most of the stopping. Prius HV coolant pump issues have been reported (MIL “on” for DTC P0A93), as have complaints of early tire wear. Nissan Altima hybrid owners have complained about dead battery issues, engine revving, the need for engine replacements, and even poor dealer service (dealer related issues are not limited to hybrids, but such complaints may work in the independents’ favor). Yes, hybrids offer unique service and repair opportunities, and if you’re not offering this, your HEV owners will likely go elsewhere for even routine brake, tire, and periodic maintenance service5.

Then there’s the even more specialized kind of HEV diagnostics and repairs. Shops are now servicing electric air conditioning compressors, electric power steering racks, HV electronics cooling systems, and so on. Along with this, an even higher “level” of HEV service is being performed which requires specialized training. This includes the high-voltage drive system(s) with previously unseen components like HV battery packs, controllers, power inverters and drive motors (electric machines).

Obviously, today’s high voltage hybrid systems are not what your shop is accustomed to servicing, and dealing with this “new” technology is where many technicians “fear to tread.” But armed with the proper training, the right diagnostic and repair tools and good quality safety equipment, technicians around the country are now offering specialized hybrid service — we’ll identify critical HEV vehicle service needs, frequency of repair, and what other technicians are actually doing in a follow-up article.

To keep customers’ hybrids going (and to fill a market demand), some independents have learned how to replace worn out battery cells and rebuild battery packs, repair and replace high voltage controllers, inverters, motor/generators, high voltage cables/connectors and so forth. Some shops are even converting Prius and Escape hybrids to Plug-in Hybrid Electric Vehicles (PHEVs) for greater all-electric vehicle range, and fuel savings of up to 100 mpg6! But remember: Before digging in, anything connected by those orange (or even blue) HV cables may be life threatening if not handled properly. But with all due respect to such high voltage wiring and components, what are you waiting for to get started?

Which hybrids should I service?

As mentioned above, the lion’s share — over 90% — of hybrids in the U.S. may be considered as Type 1 (drivetrain) hybrids. Knowing this, consider how many of these are owned by customers in your area. Knowing this will help you determine the kind of training you want to go after7, and also: 1) Where you’ll get the training; 2) What tools and test equipment to purchase, and; 3) What safety equipment you’ll need8.

Starting point

If you’re an automotive technician, you already understand 12-volt systems with high amperage. But now you’ll be focusing on high-voltage systems (50 volts and higher is considered life threatening) with less amperage. You’ll need to understand three-phase AC electrical theory which is vastly different from your legacy knowledge of 12-volt DC systems. You’ll need to understand HEV nomenclature (terminology), some of which many technicians have never even heard. If you’re not up-to-speed with these basics, attending an evening course or researching the Internet to get familiar with AC theory is an important first step in the right direction. In fact, possessing basic AC knowledge is highly recommended before attending hands-on hybrid vehicle training. The trade has advanced from interpreting transmission “stall speeds” to electric machine “slip angles” and the associated trouble codes (DTCs). New technology means new terminology, new test equipment and learning to successfully navigate hybrid vehicle scan tools.

For now, get smart

You’ve seen ‘em, you’ve learned some things about ‘em, and now’s the time to crack the books and get smart about hybrid-electric vehicles; you’ll be amazed (and frankly, awestruck) both at how mechanically and electronically sophisticated they are. With the proper training, service information, tools, and diagnostic and safety equipment on hand, the only thing standing between you and successful hybrid vehicle service is your degree of passion for learning, your level of motivation, and your desire to keep your customers’ hybrid vehicles running right!

After all, that’s what we do best!   ●

Stay tuned for follow-up articles discussing HEV training, the frequency and criticality of repairs, and what subject matter experts are now examining to keep hybrid vehicle customers happy.

[PAGEBREAK]Classification of hybrids and hybrid drive systems

A useful way to classify hybrid vehicles is to sort them by the type of drive system “architecture” they use. Some OEMs share drive-system architectures with other OEMs; some earlier-used drive types have been discontinued; others are just now hitting the market. Hybrid-electric vehicles (not plug-ins or extended range hybrids) use drive systems which seem to fall into one of four distinct types (categories), as detailed here:

Type 1 ­— These HEVs use an electronically controlled continuously variable transmission (e-CVT) with a single planetary gearset. They have high-voltage motor/generators (so-called MG1 & MG2 “electric machines”) and run in a series-parallel configuration. The vast majority of hybrids are considered Type 1 vehicles using Toyota’s older Toyota Hybrid Drive (THD through 2003),or their newer Hybrid Synergy Drive (HSD) or similar. Along with Toyota, Type 1 hybrid makes include Lexus, Ford, Mercury, Mazda, Nissan and others as full hybrid vehicles. An even newer type 1 drive came out in 2010 (See “Toyota Comparison” images).

Type 2 — To a smaller degree, hybrids use the series-parallel “2-Mode” style drive system. These drives use a CVT, a 4-speed (or more, up to 8) automatic transmission, two (or three) planetary gearsets and an MG1 & MG2. They may also employ cylinder deactivation (Displacement On Demand) at higher road speeds. Type 2 full hybrid makes include BMW, Cadillac, Chrysler, Dodge, Chevrolet, GMC, Mercedes Benz and others.

 Type 3 — These hybrids use either a manual transmission or a belt-driven CVT in a parallel hybrid configuration. A small motor/generator is located between the engine and transmission to supplement power as needed. Hondas with Integrated Motor Assist (IMA) use this system.

Type 4 — A few (so-called) GM micro hybrids used a relatively low-voltage 42 volt (3 x 12 volt) start-stop and launch assist system in conjunction with an automatic transmission are considered a Type 4 drive category. GM’s so-called PHT (Parallel Hybrid Truck) and BAS (Belt-Alternator-Starter) equipped vehicles such as the Tahoe/Yukon and Saturn Vue are considered Type 4 HEVs.

There are many variations to the above drive systems, but hybrid vehicle subject matter experts consider these (especially Type 1) to be the one’s you’ll most likely see in your shop.

Hybrid-electric vehicle drive type classifications: Types I through IV

Hybrid-Electric Vehicle Drive Type Classifications (see text):

Type I = e-CVT (e.g. Prius, Camry, Escape, Fusion, Nissan, etc.)

Type II = Two-mode (e.g. GM, Chrysler)

Type III = Belt CVT (e.g. Civic, Insight)

Type IV = Start-Stop, launch assist (GM, Chevrolet, Saturn)

Notes: The Type I drive system is the most widely used. Vehicles using a Type 4 drive system are no longer in production; start-stop equipped vehicles are not considered hybrids by everyone.


1. See:

2. U.S. hybrid vehicle sales figures by numbers and models, along with alternative fuel vehicles figures, can be found at the U.S. Department of Energy Web site at:

3. According to R.L. Polk & Co. and the U.S. Census.

4. How folks define a “hybrid vehicle” depends on who you’re talking with.

In the strict sense, a start-stop (with launch assist) equipped vehicle using an ICE and batteries is technically a hybrid, but some think otherwise.

For basic information about hybrid vehicles and other clean fuel vehicles, scroll through and find the author’s archived ASE TechNews articles about “Alternative Fuels Technology” at:—-Events/Publications/Tech-News/Archives.aspx

5. Visit the International Automotive Technicians Network ( forums to learn more about service issues unique to hybrids.

6. The market demand for PHEVs is growing and the OEMs are responding in kind.

For more on plug-ins, visit and also and sign up to keep up-to-date on exciting developments regarding PHEVs.

7. Details on selecting a hybrid vehicle training provider will be discussed in the next issue.

8. For important information on high voltage safety, go to:

Additional hybrid information will be presented in the next issue of Auto Service Professional.

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