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I have 2007 DX-G, manual transmission with 120,000 miles on it and I have been having intermittent no start/no instrument light problem since I replace both key FOB batteries.

Normally, everything appears fine; the vehicle starts and behaves like it should. However, with no warning the following will happen:

· When the key is in position 1(Acc), all is good radio comes on and power goes to the accessory port (what we used to call a cigarette lighter).
· When the key is in position 2 (Run), nothing happens and the car is dead. There are no instrument panel lights (as in no prove out of warning lights), no radio, no fan, no interior light, no seat belt warning.
· When the key is rotated to the Start position (3), nothing happens.
· I can’t hear the starter relay click at this point (as mentioned below, this relay was replaced)

At this point if you try to boost the car with one of the portable rechargeable battery devices, it will not work. If you try to boost the vehicle from another running vehicle, this is where it gets interesting. Sometime nothing happens, sometimes it works. The most recent time (today) I happened to touch the two booster cable leads together as they were connected ONLY to the dead civic, as expected there were sparks and some noise…and then the vehicle started as normal while connected to the boosting vehicle.

The last time this happened (about a week ago), I tried to “roll” or “bump” start the car by letting it roll down a bit of a hill and popping the clutch into 2nd gear. This didn’t do anything, as the car was dead with the key in the run position. After trying this twice with no effect the car “fixed itself” while I was sitting in the driver’s seat calling a tow truck. I then drove it home without incident and it was “normal” for about a week. Then it wouldn’t start again (today)

So, for some other information:

• The battery is “newer” about 9 months old and shows an approx. charge of 12.5V. The terminals are clean (and I have cleaned then in the last week) with no corrosion. It was tested at a local part store and they said it was OK.
• The car does have an aftermarket stereo and amp in it, but has had this for about 5 years without issue. As well, the secondary amp has been disconnected in case there was a parasitic draw problem.
• When the car is mis-behaving, the key fob won’t work either, but when you open the door the interior light will come on, but it appears a bit dim (it is a led type bulb and so doesn’t fade quite the same way an incandescent bulb would
• When I drive, so this is when the car is behaving normally as it started, turning on the headlights, high beams, fan on full and rear defogger does not seem to affect the headlight (the point is that under full load, the system seems OK, although the head light are those LED ones and don’t draw as much amperage as incandescent bulbs).
• The connections to the alternator look fine (clean, no corrosion)
• The Serpentine belt appears fine and is free of cracks or indications of wear. It appears to turn normally and not slip when the car idles.
• As I mentioned, the problem seemed to start after I changed both key FOB batteries. Since replacing the batteries, the FOBs work fine (locks and unlocks the doors, beeps the horn etc to acknowledge) when the car is OK, but do nothing at all when the car is “dead”. At all times the red LED on the key lights up when buttons are pressed.

What I have done so far:

• I was initially following the starter circuit, and as such have replaced the starter relay in under dash fuse panel. In terms of the starter, when the car is functioning normally, it starts with 3 to 4 cranks and sounds “normal” (by this I mean it is not making any strange noises. I have owned the car from new and have pretty good sense of what it should sound like).
• I have checked ground G401 under the dash and it is fine, with a nice solid connection to the body
• Used one of those battery load testers (which is essentially a big resistor that you can use to put a load on the battery for 10 sec or so) and the battery does not drain abnormally and the voltage doesn’t move from 12.5V.
• As mentioned, the battery was tested at a local parts store and they said it was fine.
• I have replaced the ignition electrical switch, the one the mechanical switch rotates to start the car.

As I mentioned, this problem is intermittent, and will “miraculously” fix itself and then nothing appears to be at issue. It is almost as if a relay becomes “stuck” in an off position and will not allow power through to the car (it appears dead with no indication of life) and then when the relay becomes “unstuck” things work fine. Part of the problem is that when it “fixes itself” nothing seems wrong with it and none of the components I have looked at appear broken.

So, some questions and thoughts:

• Is there some “master” relay in the IG1 circuit that could do this? I am thinking IG1 as it is a common point between the run (2) and start (3) positions of the ignition switch.
• I know that IG1 is involved in the fuel system, ABS, the gauge and the key interlock/immobilizer system. However nothing there seems to jump out as a problem. Am I missing something?
• I don’t think it is a dead/dying battery as it is less than a year old, has good voltage, passes load tests.
• I also don’t think it is the alternator or a parasitic drain for similar reasons; the car doesn’t “act” like a car with a dead/dying battery does. It is just electrically dead, that and boosting doesn’t fix the problem the way boosting normally does.
• Could it be a key recognition problem with respect to the immobilization system?
• When activated, does the immobilizer allow the car to crank? I have read that it kills the fuel system, but does it affect other systems?
• When the car is “ok”, when I insert the key, I see the green key icon on the instrument panel flash briefly. When the car is “dead” I don’t recall if I see the green key flashing or not and today the car is “fine” so I can’t tell

OK, needless to say, I am stumped and would appreciate any thoughts or advice beyond taking it to a dealership. To me the dealership is an option of last resort as, unless we get to the point where Honda specific computer diagnostics are needed, I can’t say I have not had the most positive experiences with dealership service departments.

Thanks in advance for your suggestions.

Anthony