Hi ,I have a 2007 honda civic ex...last week I went ot start it and the green key light was flashing so I guess this meant that the car was not reading the key...well I took my other car to work , came home at lunch time and the honda started...went in the house ..came out and the car wouldn't start again...green key light flashing...had it towed to the honda dealership..they said the first time they tried to start it it wouldn't start,..then they tried again later in the day and it started..so it kept starting and I was charged 60 some dollars for them to tell me there was nothing they could find...had all the codes ckecked...nothing showed up...so today after a few days of the car starting every time, I go out to start the car and nope...green key light flashing and won't start...stubborn as I am...I kepy incerting my key and taking it out about 15 times...finally the green key light stopped flashing and the car started...grr this is really a problem...wouldn't want this to happen where I couldn't get help or a tow or my daughter driving it to her work term 1 hour away!...any answers to this problem would be greatly appreciated Thanks! Margie

be sure the honda key is by itself or with only regular metal keys when starting the car. other key cards and a second key can scramble the signal. but more than likely its a faulty immobilizer security system. the 06+ civics have tons of problems with the unit.

Do you think installing a new immobilizer would fix the problem?

more than likely, but it involves reprogramming to get everything going again. if you just swap the unit out, car will never start. the immobilizer is tied into alot of systems including fuel, ignition, and main computer.

Do the 07 have a different immobilizer system than the 7th gens? If not, then when mine was blinking a new battery fixed the problem. Maybe check your battery terminals and connections to make sure they're not loose. GB didn't you have this issue a while ago too?

Thanks Gearbox

yeah the 06+ something bad happened with the immobilizers but i dont know what. 7thgen version is pretty much trouble free. i had the green key come on once after taking the car to a shop because they left the + battery terminal loose. ofcourse there were alot of other problems going along with that like flickering lights and radio losing presets.

I am having the same issue the car starts then dies. The key got stuck in the ignition so i change the ignition cylinder out and now the green key light flashes, car starts then dies. Is there a way to reprogram without taking it to the dealership?

I tried to start my 2004 Honda Civic this morning and it took about 5 minutes to start. After it started the green light is flashing. What could this be.

A weak battery and low voltage can cause weird communication problems between control units.

Charge up the battery or make sure it is good and fully charged, and recheck?

I have a similar situation,I was testing my ac line pressure switch an my car shut off. my key light keeps flashing now, check out all the fueses,good,but no change,got it reprogram, nuttin,but sense,I noticed a certain yellow and black wire only getting current wen my key is on acc,,wen before it would have been like that but it would get current for about 30sec after I take out the key but now current gose once the key is off so in convince it's a relay but no clue which one,,help please

So what do you mean by “testing AC switch”?

Who reprogrammed the ECU?

Why does that yellow and black wire stand out to you vs. all the other wires in the car?

What country do you come from that doesn’t use periods in their written language?