Honda Civic Hybrid 2 - 2006-2011 Models

Information Collective

Welcome to Honda Civic Hybrid 2 - Information Collective, here I document various bits of information on the second Honda Civic Hybrid generation (HCH2), based on the Honda Civic 8th Generation platform. Much of the information here has been gleaned from the official Honda manuals, forum's Honda area as well as Insight Central's Knowledge base as the Insight uses the same IMA technology. Big credit goes to Steve Keith for his posts at GreenHybrid and Insight Central.

Auto Stop


The Auto Stop / Auto Idle Stop feature can be one of the most difficult to grasp when driving the HCH2. It may seemingly work / not-work for an unknown reason, often leaving owners puzzled or thinking that auto-stop has stopped working. Sometimes, this is actually the case and can be easily remedied, other times it is the owner doing something they may not be aware of that is disabling the auto-stop from starting. The 2009 HCH2 Manual breaks the conditions into two categories much clearer than the 2006 manual, so that is what I have based this breakdown upon.


According to driving conditions

• The engine coolant is nearly up to normal operating temperature.
• The IMA battery is charged enough to operate the system.
• The vehicle is not climbing a hill.
These requirements are entirely dependent on the car and situation, not on driver input.

• Outside temperature is between 10-100 degrees F.
Sometimes mechanics will disconnect the exterior air temperature sensor and forget to reconnect it, this causes Auto Stop to fail. Reconnecting the sensor can resolve this.

According to vehicle controls

• The shift lever is in D or N.
• You are not pressing on the accelerator pedal.
This is where one common type of issue can occur. Aftermarket car mats can often softly touch the accelerator pedal, enough to disable the auto stop feature. This is one area to check if you are having trouble with auto stop.

• You are pressing on the brake pedal.
A common point of failure is the brake pedal switch, this is a relatively cheap part and can stop working, so while you can physically make the car stop, the car computer system does not realize you are holding down the pedal. If you have verified everything else, you may need to replace this switch. [ref]

• Fan speed lower fan speeds, in either AUTO or manual modes.
Make sure the fan speed is set to one or two bars .

• The front window defroster is off.
Make sure the MODE is not set to blow on the front window. Turn off the button and do not use the mode.
When it says "The front window defroster is off.", it actually means you cannot have the fan mode in foot vents + windshield vents mode at all for Auto Stop to function. If clearing the windshield at the start of the drive, remember to switch to front vents + foot vents mode once the windshield has cleared.

Disable Auto Stop

Switching the fan mode to window vents is a quick and easy way to switch off auto stop, if you find it problematic in stop and go traffic:

CVT Transmission

To maximize fuel economy, the HCH2 has a CVT automatic transmission that continually manipulates the gear ratios to provide optimal use of engine power. The downside of this CVT system is it is requires more lubrication, pushing all of the engine power through a steel belt, and having more moving parts [ref]. However, this is not a problem if the CVT is regularly serviced. This means a complete drain and refill of the transmission fluid using Genuine Honda CVT fluid. Aftermarket fluid or the wrong fluid (such as Honda ATF fluid - yes this has happened!) can cause lots of transmission problems.

Fluid Drain and Replace

If you have just purchased a used HCH2, it is highly recommended that you replace the transmission fluid. While owners may keep up to date with oil changes, the transmission fluid often goes forgotten - on the HCH2 it is more important than most other cars to keep this fluid clean as it is vital to keep the CVT transmission working.

Here's a quick overview of the service, however you can likely find a local mechanic to do this for you affordably. I found a mechanic who charged me $20 for the job, compared to over $160 at the Honda Dealership (although this also included the fluid).
• Purchase 3 litres/quarts of Genuine Honda CVT fluid [Amazon] (also available at Honda dealerships).
• Lift car on ramps or car lift. Note the car has quite a low front, so make sure when buying ramps they are not too steep for the front of the car.
• Use a 3/8 head ratchet to unscrew the drain plug on the fluid tin. The transmission fluid will immediately start to drain out so have something ready to catch this.
• After drained completely, clean and refit the drain plug and washer. The crush washer is supposed to be replaced with a new one every time. My mechanic had some available, but these can be purchased from a Honda dealership. Other Honda owners have reported that the crush washer can be reused [ref], but you may not get a perfect seal, so do this at your own risk.
• Refill with all 3 quarts/litres of fluid.
You can see a more detailed walk-through here: - DIY: CVT transmission fluid change.

The transmission fluid drain/refill only replaces around 56% of the fluid in the transmission [ref]. If the fluid is visibly extremely dirty and/or contaminated, or you are having serious transmission issues, you will have to repeat this process 3 times with some driving in-between to completely clear out and replace all the transmission fluid in the system. This is called the burnishing process and there are more details on this here: - 2007 Civic Hybrid CVT Fluid Change Flush DIY Very Easy Applies to 2006-2011.


The official schedule for the fluid replacement is every 30,000 Miles / 50,000 KMs. However, given the sensitive nature of the transmission, on higher mileage vehicles in particular, in addition to the fact a drain/replace only replaces just over half of the fluid in the system, it is recommended you drain/replace the fluid every other oil change to keep the CVT in perfect working order.

Engine Performance

The HCH2 has a 1.3L engine, boosted with the IMA assist electric motor. Being a smaller engine makes it more prone to carbon buildup taking away from performance. In addition, the HCH2 fuel filter and pump is located in the gas tank, making it incredibly difficult to replace should it get clogged up with gunk.

To mitigate this, I recommend the following two products:

Chevron Techron Concentrate

Chevron Techron is one of the most highly rated fuel system cleaners. It is powerful, but still gentle on components and seals it comes into contact with. It is only available in the USA, the cheapest being at Walmart [Link] for around $5. I live in Canada, but close enough to the border to drive to a U.S. Walmart and pick up a few bottles of it. I tried the STP 5-in-1 cleaner and it nowhere near made as much of a difference to the performance and reducing vibration as much as the Chevron. This will clean out your fuel system from the tank up to the fuel injectors in the engine.

For a deep-treatment, I recommend using one bottle at a quarter tank of fuel, and then another bottle at a fill up. The quarter-tank treatment will break down anything more stubborn in the fuel system.

This cleaner not only helps with fuel injectors, but the entire fuel system, helping breakdown anything blocking the fuel filter or clogging up the fuel pump. It has even been reported to fix faulty fuel gauges in other cars! [ref]

Why use this cleaner over something else (e.g. Sea Foam Motor Treatment)? As well as my own experience, read this review from "Fish":
This product is best in class. A lot of aftermarket fuel and oil additives are genuinely hokum, snake oil, and nonsense. Many are just naphtha or some other solvent, with fancy made up performance words printed on it. Techron is a state of the art fuel system cleanser Chevron developed twenty years ago that has defined the standard of clean for fuel. For years, the big-3 automakers would truck in Chevron's gas with Techron from hundreds of miles away (not sold in Michigan) to run in their cars for official EPA testing. Moreover, even the Mercedes Benz mechanic manual calls for the use of concentrated Techron to clean out certain fuel issues. This stuff is the real deal. So if your car is older, has used questionable gasoline, and could use some extra cleaning power to make sure the injectors and valves are clean and free of deposits that can interfere with good, clean running, this product is a valuable tool to help clean things up and keep the engine running well. This is stuff that I trust.

Sea Foam Spray

Sea Foam Spray lets you clean out the rest of the engine - the throttle body, the combustion chamber and everything in between. It is specifically recommended to help with smaller engines, which makes it perfect for the HCH2. It is widely available in any auto store in Canada and the USA. To use it with the HCH2, loosen the screw for clamp holding the air intake pipe to the air filter box, then remove the air filter box cover to pull the pipe away from the air filter box. Use the U-shape hook included with the Sea Foam to feed the spray-tube around down the pipe to go towards the throttle body. This bypasses the air filter itself and the O2 sensor, which is important. Sandwich the hook inside the air intake pipe and reattach the air filter box cover - essentially restore it to how it was before but leave the hook in place. You might not be able to retighten clamp on the air intake pipe to seal it completely which is OK for short-term use as you use the Sea Foam spray.

Start the car, leave it in park and and keep the handbrake on. Once the car has warmed up, have a friend rev the engine and keep it between 2000-3000rpm, attach the spray-tube to the attachment on the top of the Sea Foam spray-can and start to spray through the tube. Be advised it can take awhile to empty the can! Once done, let it soak in the engine for at least 15mins, remove the hook and restore the air filter pipe to how it was before. You may have to pull everything apart again to remove the Sea Foam Spray hook and put everything back to how it was before.

Gently drive the car to somewhere quiet, like a backroad or rural area, then push the throttle hard. This will produce a huge cloud of smoke out the exhaust (why it's better to do this away from people!). Keep driving the car aggressively until all the smoke has cleared out.

For my HCH2, this product made a huge difference - improving throttle response, smoothness and engine output power. The battery gauge charges up noticeably faster as there is more engine power available to charge it.


How often you use these products is up to you. The Chevron recommends every 3000 miles, but I personally feel every oil change is probably sufficient. With the Sea Foam, again every oil change is likely more than good enough, perhaps even every other oil change depending on the car performance.

Tire Pressure

The standard tire pressure recommended by Honda is 32psi. However, many drivers have reported success at using higher pressures to improve fuel economy. Two things to keep in mind - firstly verify the tire wall strength can handle this pressure before proceeding with it. Secondly - higher tire pressure may produce better fuel economy, but has worse ride. The 32psi was recommended by Honda for their ride requirements [ref]. I have the tire pressure set to 36psi. A little above standard just to get a bit better fuel economy, while remaining comfortable. Experiment and see what works best for you.

If the tire pressure gets too low from a slow leak or puncture, I have noticed in my own experience that this can cause power surging and pulsing acceleration problems. The IMA engine does not like having to push along deflated tires!

ECU IMA Update

In 2012, Honda released an update for the IMA system used in the HCH2. The purpose of this update was to increase the lifespan of the battery. As the owner of a 2006 HCH2 with the original battery still working in 2018 that got the update, I'd say it works to preserve battery life, though I could just be lucky! The update essentially works by preventing a deep discharge of the battery, which is known to harm NiMH batteries, such as the cells used in the HCH2 battery pack.

The Toyota Prius already had a similar mechanism in place to limit NiMH damage since day one, called hypercycles, which is likely why Prius batteries have lasted better and probably a big contributor as to why the HCH2 has received a bad rep for dead batteries - some HCH2s didn't get the update soon enough or never went back to the dealer to get the update. If you suspect your HCH2 hasn't been updated, it is highly recommended you take the car to a Honda dealership to get this update installed. If you don't update, it is recommended you try to prevent the Battery Level Gauge going below 2 bars when driving [ref].

How to tell if your Honda Civic Hybrid has the IMA ECU Update to Extend Battery Life

If your battery gauge rarely goes below 3 - 4 bars, even under hard continuous acceleration, your car has the IMA ECU update.

In the owners manual, it states that "The gauge reading may drop near the bottom under driving conditions that require IMA motor assistance for a long time, such as prolonged acceleration or climbing a long hill. The IMA motor will recharge the battery as you continue driving.". This was the original behavior of the Honda Civic Hybrid IMA ECU, to completely drain the Hybrid battery to assist with long hill climbs. After the update, this no longer occurs and the system will not let the battery drain that low.

This was at the expense of some fuel economy, since it essentially reduces the usable capacity of the battery, but better to spend more fuel than have more frequent battery replacements!

Hybrid Batteries

The statistics on the HCH2's hybrid batteries are grim. A survey by consumer reports showed a 30%/32% failure rate for 2009/2010 Honda Civic Hybrids respectively [source].
Battery replacement rate cited by 2013 survey respondents
Model year Civic Hybrid (%) Toyota Prius (%)
2006 14 3
2007 12 1
2008 8 0.5
2009 30 0.3
2010 32 0.1
It is uncertain why the later models have higher failure rates, possibly as NiMH became phased out and more investment went into Lithium Ion, there may have been a quality drop in the cells produced. This is something to keep in mind when buying a used HCH2. Some people cite this as a reason to not buy a used HCH2 at all, however, I still see enough of them on the road in working order to believe that there are still good ones out there, and can be a very affordable car with great fuel economy, despite the maintenance risks. As mentioned above make sure your car has the ECU IMA update to extend battery life, this update was released in 2012 and some HCH2 owners never took their car back to the dealership to get this update, which could even be a explanation for the failure rates shown here.

If you are thinking of getting a used HCH2, be smart about it. Don't go for something with very high miles or kilometres, and during the test-drive make sure there are no IMA lights on the dashboard, and keep an eye on the battery level. Learn to watch for recalibrations (see below.)


Recalibrations of the battery can occur from time to time in normal operation. As described in the manual:

The battery level gauge does not read the battery level directly. It calculates the level by continuously measuring the current flow, voltage, and temperature.

Since the level is not read directly, small sensing errors can, over time, cause the gauge to read higher than the actual battery level. The system will then perform a correction, and the battery level gauge reading will drop suddenly. When this happens, IMA assist and Auto Idle Stop are disabled until the IMA battery is sufficiently recharged by normal driving. This should take only a few minutes.

This correction of the battery level gauge is normal and does not indicate a problem.

However, frequent recalibrations do indicate a problem. If you see the battery level gauge keep dropping and re-filling, even with no IMA light, this can indicate a fault in the battery.

Slow charging

You might be wondering why the battery gauge isn't charging up very fast. This can be down to several reasons, but here are some common ones:
• Cold Temperature
When the outside/inside of the car is very cold, the batteries cannot be quickly charged without causing damage to them. The system may show a large "charge" amount when braking, but this electricity is not sent to the battery if it has not warmed up. This is normal behavior.

• Low 12V
If the car has been sitting for a while, the 12V Battery may be low. The hybrid uses a DC to DC converter to charge the battery, which will take some charge away from the Hybrid battery. Most of the time this is normal behavior, however it can indicate a weakened 12V battery if it persists.

• Low Engine Output Power
During regular acceleration and cruising, the hybrid battery charge works by siphoning off a small amount of power from the engine that the car "doesn't use" to charge up the hybrid battery. If the engine is not running well, there's less power to go around to move the car, and the battery will charge at a much slower rate, or not at all. Check your motor oil is good, the air filter is clean, tire pressures are correct, and consider using the engine performance products I recommend above.

Battery Refurbishment

Since the batteries are comprised of multiple sticks comprised of multiple D cells, sometimes you can mix and match sticks to produce one working battery. This is really the only viable way to refurbish a battery.
Charge cycling is often suggested a workable method, but in reality it's very difficult to restore the life into dead cells. S Keith gave his thoughts on it here: - Stick refurb via cycling - why it's a waste of time.

Replacement Batteries

Where do you turn when the battery completely dies? Panasonic are no longer manufacturing the original D-sized NiMH cells used in HCH2, which were extremely high quality, made in Japan and able to handle high recharge loads without failing.
• Honda may still cover your battery under an extended warranty - USA only. If not, then they will still be able to sell you a replacement battery pack with these cells, but they are simply reconditioned from other vehicles, not truly new. They will also charge you a hefty price for it.
• Alibaba has replacement cells for sale, but these are manufactured in China to a lower standard than the originals, and will likely have a very short lifespan. There's a discussion about this on the Honda Civic Hybrid facebook group: Facebook - Honda Civic Hybrid [IMA] - "Has anyone tried the 10k sticks on allibaba?"

Recommended option: Bumblebee Batteries offers a replacement battery pack for just over $2000 USD, provided you send in your original pack to them. This even has a 3 year warranty. They are using made-in-china sticks, but they thoroughly test every single cell inside the sticks to match them and make sure they are to a high standard [ref]. Bumblebee have a useful page that covers the facts about battery replacement: Bumblebee Batteries - The Straight Facts About Honda Hybrid Battery Replacement.

Despite Bumblebee using the top-quality NiMH cells available on the market right now, it seems as though they don't match the quality of the original OEM packs. Even with Bumblebee's stringent testing and requirements, there have been reports of them failing after 50,000 miles, with OEM packs able to reach 150,000+ miles. This is just a reality of the Panasonic Japanese NiMH cells no longer being manufactured.

Above: Email from a Maxx Volts charger customer - their Bumblebee battery pack failed after 50,000 miles, compared to 150,000 miles on their OEM pack.

Driving without IMA / Not using Battery pack

The last bastion of the failing hybrid is driving without the IMA assistance entirely. This means your almost 2 ton vehicle is being powered along by a tiny 1.3L engine. While this is fine for cruising along on a flat highway, starting from a stop is normally assisted by the IMA motor, and without it, the car feels sluggish and very heavy. Going up a hill harder as well, and feels more like an old timey car from the 60s or 70s. It also means that your car will no longer meet it's original emissions targets that it had with a working hybrid system, which can cause issues if you live in a state or province that requires vehicle testing.

However, is it possible? Kind-of...

Remove the rear seat-back and the rear seat cushion, and you will find a master switch behind a cover to turn off the IMA battery. Switch this off, and your car will still work as normal in an "IMA-off" mode.

[images source]

The upside of this is that if your battery has problems, or is having frequent recalibrations, switching it off will stop the hybrid system sucking power from the engine completely and can actually improve the car performance with a dead or dying battery.

The only thing to keep in mind is keeping the 12V battery charged.
The HCH2 does not use an alternator, but instead a DC to DC power converter to convert IMA power into charging the battery.
The 12V battery will still charge at 1500-3500rpm[ref] in IMA-Off mode. So the key here is to not leave the car idling for too long at lower RPMs as this risks depleting the battery.
This has also been confirmed on in the Facebook - Honda Civic Hybrid [IMA] Group:

One source reported that the 12V battery will not be charged at all[ref]. This was likely caused by another fault in the IMA system. The solution (if you have a garage) is to buy a trickle charger and keep the 12V charged from that, but this obviously isn't ideal. - Is it possible to disable the IMA?


If you have any questions about your HCH2 I recommend making a thread in the HCH2 forum.
You can also send me a PM over at the GreenHybrid Forums, my username is CanadaJimmy.
I do have an email set up for this site if you prefer to reach me that way -

My 2006 Honda Civic Hybrid

Purchased used in August 2018, my 2006 Honda Civic Hybrid has proved to be a dependable car. I wanted something good on gas, cheap to buy, and reliable, but also up to modern safety/comfort standards and so far it has lived up to those expectations.

It cost me $5300 (canadian dollars) to buy, and gets around 6.0-6.3l/100km (40-37 US mpg) on my daily commute of around 70% highway, 30% stop-start. It had just under 140,000KMs (86,000Miles) when I bought it. I'm hoping it will last me at least 5 years, at which point I'll likely transition to a fully electric vehicle.

It is painted in the NH-684P Sparkle Gray Pearl colour.

It's 12 year old hybrid battery still works beautifully, the IMA charges and assists as expected, the transmission works perfectly after a single drain/replace (with some minor gear slippage before), and it actually can sometimes be a fun car to drive! It has very good precision handling that makes it easy to turn the car where you want it to go. The legroom is decent, I have long legs and in this car I can move the drivers seat far back to drive comfortably. The AUX jack is great too - with a phone mount I simply use my phone as the in-car entertainment and can accept hands-free calls.

When I got the car, it had an issue when idling without auto stop, the idle was a little unsteady and even sometimes went a bit crazy, but after using 3 bottles of Chevron Techron (adding one when the car was at a quarter tank for a more concentrated treatment), as well as Seafoam Spray through the air intake, the problem is resolved and idle is nice and steady. Either this was a clog in the fuel system somewhere that the techron broke down, or carbon build up on the throttle body or elsewhere that the seafoam spray cleaned out. I have details of these products above.

I've never owned a car that had so many bits of hidden knowledge that inspired me to put together a page like this! So that has been a fun part of owning this vehicle.

To me it is the perfect second car for my household - I'm not sure I would be happy with it as my only vehicle, but for a cheap car for commuting back and forth to work, racking up kilometres all while just sipping a tiny bit of gas, it's pretty unbeatable in my opinion.