Hello,

I have been working on a p1509 code in my 1999 Honda Civic EX Sedan. I changed out the Idle Air Control Valve, Checked the wiring, and then decided to swap the ECM.

I swapped the ECM with one from a reputable Ebay salvage company. I put the new ECM in and the car won't start. It will turn over but not start. I put the old ECM back in and the car won't start. I unplugged the negative terminal while swapping the ECUs.

I checked all the fuses that are related for continuity. Then I tested the Main Relay and got power to the three input wires. The constant power was 12v, key to acc was 12v, and power when starting only was 9.4v. I plugged the relay back, turned the key on acc, and tested the two output wires. The yellow/black wire showed power. The yellow/ green did not. I bought a new relay and the car seemed to run for a split second then died. It may have not fired up, it happened to quick to tell. I tested the new main relay and it had the same results as the old one. The yellow/ green wire doesn't show power.

If I unplug the relay, then turn the car over, and then plug the relay back in. The car seems to fire for 1/2 second then die. The CEL light doesn't come on with the main relay unplugged.

Would it be possible to fry a main relay like that?

 

I swapped ECU's in my 1999 Si and when I did this, it blew the ECU fuse under the hood. Might want to check there. I don't believe it was called 'ECU' fuse, but might want to take a look there to see if it's blown. Also caused my fuel pump to not come on.

 

I checked the 7.5 amp under the hood marked backup/ radio. Is that the ECU fuse?

 

I also checked the one next to it called EM/ I and it was OK.

 

Assuming this is a crank, no start ...
back to basics ...
check for spark
check for fuel injector pulse
listen for fuel pump to prime fuel rail when key is first turned to on position
check timing

 

I got the car to start by jumping the yellow and green wire on the main relay to ground. It sputtered for a bit but started. It has been starting no problem all day.

Does the new ECU need to be programmed to my car?

THanks for the help,

Bill