Last week the “Check Engine” light came on while I was passing. My morning commute is 40 miles on two-lane roads with limited passing lanes. When I can, I accelerate smoothly without a transmission downshift. But, when I need to get around, I get around, and this was one of those times, throttle down enough to call IMA and tranny downshifting. About half-way through the pass the engine seemed to lose punch and acceleration. In the old days, I might have thought “misfire in one cylinder” or “carb mix problem,” but on newer cars I frankly have no idea. My response to the loss of power was to add more throttle, close to flooring it. Engine responded, and I got around, but the “Check Engine” light started flashing after this second throttle. I’ve done similar passes before in the car’s 4000 miles with no problems.

Car seemed to run smoothly enough with the CE light on, though I did pull over within a couple of miles; by this time the CE light was steady on instead of flashing. Turned off ignition. Checked the owner’s manual. From some other car Check Engine experience I knew that the indicator can mean very bad news, or indicate a loose gas cap, or some “transient event” that trips the indicator requiring “fault codes” to be cleared and all will be well, or something in between. Owner’s manual guidance leans toward suspecting the worst. Restarted, check engine light still on, but smooth idle, no signs of a problem with other gauges, so I drove at 50 miles per hour the ten miles on to work with no problems. Called dealer and talked to Honda service dept; I’m their first HAH customer, so they have no repair history for the HAH. His advice was to drive as little as possible and cautiously, watching for other signs of trouble, and to come in ASAP, which I did the next day.

Driving about 60 miles with the CE light on, I noticed that the ECO light never came on (I’ve been driving to keep it on as much as possible), although the battery charge and IMA indicators operated as before. Trip computer indicated that either the 6-cylinder mode can produce 32 mpg, or that VCM was still working even though the ECO indicator light was not on. I suspect the latter.

This was the Honda tech’s first hybrid work other than dealer prep checks. He reported that the diagnostic computer “could not communicate” with the car’s engine control module, so he was unable to observe a particular “fault code” that called the CE light. The fix was to “reboot” the control module and “reset” it. He advised me to monitor all gauges/lights closely for awhile since he could not tell whether the CE light was from isolated, transient event, or a sign of a more serious mechanical or computer module problem. He could find no cause for the CE light other than the glitch in the engine control module. He said the increased throttle for passing could have triggered the CE event, but should not have, but without a stored fault code, he'd only be guessing. All functions are back to normal since the reset; batt charge, ECO, and IMA indicator lights all back.

One added item, related to another thread here on HAH battery charging. The tech said the hybrid battery was low (my claim is that it was at least 3 bars, and more likely 4 which is what I see 90% of the time). We talked about “bars” of charge a bit, and it was clear that he did know how many “bars” the charge indicator had. I’m assuming he relied on a charge meter for his diagnosis. He said that the batt was now “fully charged.”

Indeed, all 6 bars of the charge indicator were lit when I started the car after the service, the first time I’ve seen 6 bars lit. I didn’t observe how he produced the 6-bar charge, but I don’t think it was from driving. IMA was very active in city traffic after leaving the Honda shop; within one mile the batt charge was down to 5, and within two miles, it was down to 4 bars again, where it has stayed except for some brief 2-3 bar times after hill climbs with IMA. I’m thinking there must be a difference between “full” charge and a “functional” charge, and that while 6 bars may be “full,” it’s not really a normal, functional batt charge level which in my car is a 4-bar charge.

Trip computer mpg and overall feel/sound/performance indicate the car is running as it was before the CE light incident. I don’t really have any questions here, but offer the info to add to the HAH knowledge base, and for comment and perspective from more experienced hybrid drivers.
Lewis