P1456 is an OBD-II trouble code indicating a small leak has been found in your Honda Civic's EVAP system. This is most commonly caused by a fault gas cap. The fix simply requires purchasing a new gas cap and allowing your Honda's ECM (engine control module) time to recognize the repair, clear trouble code P1456 from memory, and turn off the check engine light. If the fault is more serious than a defective gas cap or if the check engine light immediately illuminates after the trouble code(s) are cleared from the ECM using a scan tool, then you must diagnose the fault further, inspecting EVAP system hoses and vapor lines between the charcoal canister and gas tank, as well as the electronic components which control and measure gas tank vacuum/pressure. It is recommend to have a smog check repair station with the proper EVAP testing tools perform a thorough diagnosis.
Trouble Code P1289 is related to your Honda Civic's Electric Load Detection (ELD) Circuit. OBD-II P1289 indicates your Honda's ECM detected a problem with the load detection system, and has been unable to determine correct electrical load. Without this information the ECM is unable to command the alternator charging system. P1289 can be caused due to a defective:
Electronic Load Detector Unit
Electronic Load Detector Unit harness is open or shorted
Electronic Load Detector Unit circuit poor electrical connection
and in rare cases... a defective ECM.
The ELD is located in the underhood fuse box. If found to be defective, replace by removing the two fuses attached to either side, as well as metal plate inserted through the ELD. The ELD uses the metal plate to measure amperage and report the data to the ECM.
Testing the ELD requires you remove the bottom panel of the fuse box in order to expose the ELD connectors. The wire on the far left of the connector is voltage signal wire (5v) from the ECM. Under increased load, such as when your Honda Civic's lights are on, the signal voltage should be low. If you see that voltage is steady regardless of engine load, the ELD might be defective. If voltage is near zero, you should unplug the connector and check to see if any voltage exists at the wire coming from the ECM. If no power from the ECM, you'll need to test for voltage at the ECM connector.
