i have a 92 civic ex p28 auto ecu. my problem is i get no codes when jumping the ecu service connector... my cel comes on when i turn the key to ON but when starting the car it turns off like normal. Ive tried disconnecting oil/iac/o2/tps/vtec sensors and i still cannot get a CEL. the car seems to run ok, although no vtec from what i can tell. its not in limp mode as far as i can tell. when i disconnect tps etc it runs poorly, so i know the ecu is working but i dont know why i cant get any service codes....

I've replaced the ecu with one that thats been tested to work properly so it cant be the ecu causing the problem.. i thought maybe there is a ground issue but im not sure how to pin point this.

any help would be much appreciated.

 

When you turn the key on but don't start, the CEL should come on for 2 seconds then go out. This will be exactly synchronized with the main relay clicking and the fuel pump starting and stopping. The CEL should not stay on unless the test jumper is in place.

Disconnect the battery, unplug all the plugs from the ECU, then reconnect the battery and turn the key on. The CEL should, of course, not turn on. If it does, someone has installed a circuit to cheat on smog checks by faking the CEL.

 

Ok I'll give that a shot and post the results when I get home from work. Thank you

 

Ok so I did I it. the cel is on when I turn the key to the on posisition.

how would I go about finding the circuit that's been installed to cheat the smog check?

 

It's going to be somewhere along the CEL wire, which is green with an orange stripe. It starts at the ECU pin A13 and goes to the cluster. When wire is grounded and key is on, CEL lights. If wire is open the CEL stays out. If you didn't see anything not stock at the ECU it is probably behind the cluster.

 

ok thanks. I'll give a look. seems strange that someone would install that kind of thing. why not just fix the broken sensors.... It's obd1, easy