Toyota Prius 2004-2009: common problems, fuel economy, photos

Updated: September 30, 2022
If any car can be called a game changer, it's certainly the Prius. The technology is simple, yet brilliant. The small transmission has a sun gear unit and two small electric motors.
Toyota Prius 2004 interior Toyota Prius 2004 interior.
The transmission takes care of the gear ratio changing, starts the gasoline engine when needed and re-generates electricity.

Nothing beats the fuel economy of the Prius. No wonder, it's the best-selling hybrid. Is the Prius dependable in the long run? How reliable is the hybrid technology? How expensive are the maintenance and repairs? Let's look at it closer.

Powertrain: The Prius's 1.5L gasoline engine is similar to that of Toyota Yaris, but is modified for hybrid powertrain. The hybrid "transmission" unit contains two electric motors that can work as generators. One electric motor controls the gear ratio and recharges the hybrid battery. The second motor propels the vehicle at low speeds and supplies additional power on acceleration. The second motor is also used to recover energy when braking or coasting. Scroll down to the 'Resources' section for more detailed info. The hybrid battery is placed under the trunk floor, see the photo below.
Fuel Economy: The EPA rates the 2004-2009 Prius at 48 mpg city, 45 mpg highway and 46 mpg combined. It's actually not that difficult to get these numbers in real-world conditions. In fact, the best fuel economy we were able to get out of this 2004 Prius is 54.6 mpg combined (4.3 L/100km). On a one-day road trip, we easily got 469 miles (755 km) on a 11.9-gallon tank (45 liters).
Toyota Prius 2005 engine Toyota Prius 2005 engine. Photo: Toyota.

Timing belt or chain: The 2004-2009 Prius engine has a maintenance-free timing chain, there is no timing belt.

Handling and ride: The Prius handles OK but not sporty. The ride is soft and fairly quiet. Thanks to the electric motor, the Prius is quick off the line. You will also appreciate the small turning radius and good all-around visibility.

Toyota Prius energy monitor Toyota Prius energy monitor.
How the hybrid powertrain works: When you start moving slowly, the car drives on the electric power alone. As you accelerate past 15-20 mph, the gasoline engine kicks in. When you stop at the red light, the engine shuts off. As you step on the gas, it kicks in again. When you coast or lightly apply brakes, the transmission re-generates the energy to charge up the hybrid battery. You can see the power flow on the center display.

Driving the Prius in winter: First, the bad news: the low clearance and lack of torque make driving the Prius in deep snow difficult. The fuel economy suffers too: gas mileage drops to 38-39 mpg combined. Now, the good news: we drove the Prius many times in snowy and icy conditions, and found that it holds the road well.
Toyota Prius cargo bin Toyota Prius cargo bin.
It looks like the weight of the hybrid battery over the rear axle makes the car more stable and less likely to skid. Another advantage is that it takes only a couple of minutes to fill up the Prius at a gas station because of its small gas tank, so you don't have to stand too long in freezing weather.

Maintenance costs: The Prius is actually not very expensive to maintain. Tires are cheap. Brakes last over 60K miles because of the regenerative braking. There is no alternator and there is only one tiny drive belt that drives the water pump. The belt is cheap and takes a few minutes to replace.

The Prius engine runs on conventional 5W-30 oil and takes only 3.9 qt. (3.7 liters).
Toyota Prius hybrid battery Toyota Prius hybrid battery
Oil changes need to be done every 3,000-5,000 miles, depending on your preference. An air filter costs around $20 and it is easy to change. The cabin filter is also easy to replace (it needs to be replaced every 30,000 miles or more often if driving on dusty roads).

Hybrid system maintenance: The hybrid system doesn't really need any maintenance. The 2008 Prius maintenance schedule mentions changing inverter coolant at 100,000 miles and every 50,000 miles thereafter and inspecting the transmission fluid every 30,000 miles. In our 2004 Prius, we changed hybrid transmission fluid at 60,000 miles, and it wasn't even dirty.

Hybrid battery: According to many sources, the Prius hybrid battery doesn't fail very often. Our 2004 Prius still has the original battery. Replacing a hybrid battery at a dealership will be expensive, but there are alternatives.
Toyota Prius 2004 2004 Toyota Prius.
For example, we found that a used or remanufactured hybrid battery can be purchased on eBay for half the price of the OEM battery. Some owners mention replacing separate battery modules (which, of course, should be done only by a qualified technician observing all safety precautions). The 2004-2009 Prius has 28 individual modules in the battery pack and we found separate modules sold on eBay for a reasonable price.
The codes P3000 or P0A80 are usually caused by a failed hybrid battery. Replacing a hybrid battery in a HV-certified repair facility will cost around 2.5 hours of labor plus the part.

Pros: Fuel economy, spacious cabin, visibility, front headroom, cargo space, large storage bin, low maintenance, takes a very little time to fill up, extra weight on the rear axle keeps it more stable, brakes last longer.

Cons: Lack of driver's seat height adjustment, interior materials could be better, low clearance, not very good in deep snow.

Common problems: There are several often mentioned problems.
Toyota Prius 2004 interior Toyota Prius 2004 interior.
In the early 2004-2005 Prius models the Multi Function Display unit may become inoperative. The first symptom is when the display at times doesn't show the state of charge of the battery and becomes slow to react. Our 2004 Prius have had this problem. We found this post documenting the repair. The Toyota solution is to replace the unit, which is quite expensive, although there are remanufactured and used units available on eBay and other sites.

The code P0a93 can be caused by a failing hybrid cooling pump. Replacing the pump is a fairly simple repair. Watch these videos.

A leaking engine water pump is mentioned often, the repair cost $350-$450.
HID headlights seem to be another trouble spot. The first symptom is that HIDs start flickering and work intermittently. Toyota parts are expensive, but aftermarket HID units are available.
A failed wheel bearing may cause a humming or rumbling noise. Replacement of the wheel bearing costs $350-$480.

Is the Toyota Prius 2 a good car to buy? Most Prius owners are quite happy with their cars. One of the questions in the annual Consumer Reports survey is "would you get this car if you had it to do all over again?" Guess what, 85 percent of Prius owners answered "Yes" which is the highest rating among small cars; read more in this CR article. Overall the Prius is very reliable. We drove the Prius for 3 years and it was the best car we had except for the not very comfortable driver's seat and not-so-sporty handling. It's a very practical car with a spacious interior and plenty of cargo space. The visibility is great too. Given its incredible fuel efficiency, the Prius 2 is often used as a delivery car. If you have a long commute and spending a lot on gas, the used Prius will pay itself off in a few years in gas money savings.

What to look for when buying a used Toyota Prius: The main question buyers of used hybrid cars have is what is the condition of the hybrid battery. Unfortunately, there is no simple way to test the hybrid battery; even the procedure described in Toyota technical literature for technicians is quite complicated and time-consuming.

What you can do is to test drive the Prius in all modes: driving slow on battery power alone, accelerating, coasting and decelerating. The battery state of charge is shown in bars on the center display. As you know, over time any battery loses some of its capacity. A battery with lower capacity will not hold the charge well and will drain faster with use.
Toyota Prius state of charge Toyota Prius state of charge.
If the battery has low capacity it will take less time to recharge.

If you were to drive two Prius cars one with new battery and one with old weak battery, you'd notice that the new battery will hold the charge longer and will take more time to recharge on the same drive cycle. If you test drive several vehicles, you might be able to see the difference.

We did a little test with our Prius. We found an empty road and tried to drive it with the A/C off at slow speed (under 15 mph) so it will run on the battery power only. The battery state of charge dropped from 6 bars to 4 bars after driving for just under one mile. Our Prius had an old original battery.

Beside, that, the Prius needs to be inspected similarly to any other car. Read more: How to inspect a used car - illustrated guide. It's also a good idea to arrange for a used car inspection at a different Toyota dealer.