Hi I have a 93 honda civic EX with a d16z6 the entire car is stock except for the radio. The problem I've been having is the CEL wont turn off when I turn the causing it not to prime my fuel pump/injectors. It's been doing this since day one when I got the car. Now I've read lots of threads saying change the main relay but I bought one brand new from honda for $80 and it still does it. It's real bad in the summer when I wake up in the morning take like 2-10 mins for it to turn on also when it rains but in the winter it's perfect turns on with no problems. But the problem im having now is the CEL won't turn off at all I can leave the key on for 1 hour and nothing. Ive run out of ideas can someone please lend me some suggestions. could it be the main relay? ECU? Or something else? Thank you for your time hopefully we can get this solved so if someone else runs into problem we can also help them

 

Anyone?

 

I'd resolder the main relay anyway even though it is "new". Also check the ECU system ground wires on the thermostat housing. Once you're sure it's not the main relay, the next part to consider is the ECU, they do occasionally do this.

 

Im probably gonna have to go with the ECU on this one. I check the grounds at the thermostat and they are good. The soldering on main relay look good they have that 45° angle on it plus Im sure I would **** up the solder but I hate to think 2 main relays are bad. Last but not least the ECU would be my guess but I won't know till I can find a 93 civic ex P28 automactic tranny, which seem to be impossible to find in tampa fl

 

It can be the ECU as MK said but one question......Did you disconnect the battery at all when changing the Main Relay?

 

No but ive I never have in other situations when this situation keep repeating itself and I was removing main relay.... Idk if that helps or not?

 

Disconnect the negative battery cable for 5 minutes, reconnect it and drive like normal..see if the cel light pops up again.
Have to rule out all the small stuff before moving on to the big stuff.

 

I ended borrowing someones ecu and it turns out it was my ecu. The moment I turned the key the car turned on and when he put my ecu in his car it was acting the same as when it was in my car so its definitely the ecu. Now my only problem is finding one

 

Try ebay or rockauto, or google it on the shopping section.

 

Auto ones should not be too hard to find. Everyone wants the manual P28. I thought there was a way to move resistors inside and reprogram an OBD1 ECU from auto to manual but I don't know if it works in reverse. The manual ones may not be built out with the hardware to drive the auto transmission solenoids.