The 2007 Civic hybrid's Integrated Motor Assist battery is the chronic problem. Owners describe the battery draining to zero bars, especially in summer heat or humidity, leaving the car running on gas engine only with poor acceleration. One owner's battery failed completely by 54,000 miles after two years of warnings; another's drained in humid conditions starting summer 2007 with increasing frequency. Fuel economy dropped from 45 mpg to 32-34 mpg for multiple owners. Dealers attempted software reprogramming twice on one vehicle; Honda told dealers they were aware of the issue but had no fix.
Fuel tank lacks internal baffles—one owner's tank ruptured when a tire hit wood at highway speed, and another reports constant fuel sloshing sounds during braking and acceleration. The replacement tank came with no protective guard.
Early ownership brought idle problems: RPMs dip and the engine nearly stalls when adjusting the sunroof or power windows at idle. Cold starts are rough and delayed after the car sits. One SI model owner reports the electronic throttle sticks after releasing the pedal during shifting or slowing, requiring aggressive braking and premature brake wear. A fuel door latch cable broke, trapping the owner at a gas station.
Failure modes owners describe
IMA (Hybrid Battery) Malfunction and Failure
The Integrated Motor Assist system fails to hold charge, causes erratic performance, and eventually fails completely. Battery indicator drops to zero bars; owners report sudden loss of electric motor assist during driving, reduced acceleration, and inability to maintain safe highway speeds. Multiple software updates attempted but did not resolve the issue. Several owners report battery completely drained under humid or hot conditions without warning.
When: Started mid-2009 for some owners; early and frequent for others starting within first year of ownership (one owner: 05/01/2009 first reported; one battery failed 12/09/2010 at unspecified mileage; another owner reports summer 2007 onset with increasing frequency through 2008; warm weather and humid conditions trigger failures)
Symptoms owners cite: Battery indicator drops to zero or single bars; Acceleration feels rough and diminished; Significant loss of power when accelerating or passing; Inability to maintain safe speed on inclines; Unexpected surges when braking; Fuel economy drops from ~45 mpg to 32-34 mpg; Sudden, erratic power loss while driving; Check Engine light and IMA warning lights illuminate; Battery drains completely under humid conditions
Codes mentioned: IMA system warning indicator, Engine Check Light, 21 error codes reported (one owner)
Repairs/costs cited: One owner reports IMA battery replacement under warranty (12/09/2010); multiple software reprogramming/updates attempted by dealers (07/10/2010, 07/26/2010) without success; dealer diagnosis difficult, with multiple error codes requiring Honda engineering consultation
Recalls/TSBs owners mention: Honda issued software updates and attempted reprogramming; one owner mentions Honda recall 07V399000 (wheel bearing, not IMA); dealers contacted Honda engineering who stated they were aware of the battery drain problem but had found no solution; second software update offered but reported as ineffective by owners
Fuel Tank Design Deficiency
Fuel tank lacks adequate internal baffles or protection from road debris. One owner reported fuel tank rupture when front left tire struck wood at highway speed; another owner reports fuel sloshing sound inside tank during acceleration and braking, indicating missing or inadequate internal baffles typical of other vehicles.
When: One incident at 54,000 miles; sloshing reported as ongoing issue
Symptoms owners cite: Hole/rupture in fuel tank from road debris impact; Gasoline leak from tank; Loud water-rushing sound from rear underside during braking and acceleration; Fuel sloshing inside tank during vehicle motion
Repairs/costs cited: Dealer replaced fuel tank at cost of $640.00 (plastic tank without protective guard); owner concerns that replacement has no guard to prevent recurring damage
Idle and Cold Start Malfunction
Engine RPMs dip and car shakes or nearly stalls when opening/closing sunroof or power windows while engine is at idle or warm. On cold start after vehicle sits unused, car does not start on first attempt, then starts roughly with significant shaking for 3-5 seconds.
When: Started at approximately 400 miles; cold start issue at approximately 600 miles after extended rest
Symptoms owners cite: RPM dip when sunroof or windows operated at idle; Car shakes at idle; Engine almost stalls; Delayed cold start; Rough engine start with jolt and shaking for 3-5 seconds
Repairs/costs cited: Dealer performed PCM reset and idle relearn procedure at 400 miles; did not resolve problem
Recalls/TSBs owners mention: Dealer reported issue to Honda Engineering who stated they had no knowledge of the issue and offered no advice
IMA Regenerative Braking System Interference
Regenerative charging system interferes with normal braking and acceleration, causing unexpected power surges when coming to a stop and random fluctuations in brake pressure. Owner describes system as fighting the vehicle's acceleration during deceleration.
When: Occurs intermittently
Symptoms owners cite: Unexpected power/acceleration surges when braking; Random changes in brake pressure required on pedal; Compromised ability to safely judge braking distance and speed; Regenerative system fighting vehicle acceleration at stops
Drive-by-Wire Throttle Retention (SI Model)
The electronic fuel throttle system on the 2007 Civic SI continues to hold accelerator position even after driver's foot is removed from pedal, particularly during gear shifts or deceleration attempts. Similar issue was addressed in TSB for 2006 model but correction not adequately applied to 2007 model.
When: Present since delivery or early ownership
Symptoms owners cite: Accelerator appears stuck after foot removed from pedal; Condition occurs during gear shifting; Condition occurs during deceleration attempts; Requires excessive braking force to compensate
Repairs/costs cited: Excessive brake wear reported due to compensatory braking
Recalls/TSBs owners mention: TSB released for 2006 Civic SI to address issue; correction not applied or insufficiently addressed on 2007 model
Fuel Door Latch/Cable Failure
Gas cap door lever fails, mechanism breaks on cable that runs from driver's seat area to fuel door. Owner unable to open fuel door to pump gas.
When: 01/15/2011 (specific date provided by owner)
Symptoms owners cite: Fuel door lever unable to open fuel door; Cable mechanism broken; Access to fuel tank blocked
Repairs/costs cited: Owner had to dismantle component from within trunk to open fuel door; repair costs not provided
Synthesized from 10 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.