My 1997 civic will not start. I pulled the codes and got PO135 and PO420. Code PO135 is O2 sensor heater circuit malfunction(bank 1 sensor 1) Is there a sensor to change and where is it located. Thanks

 

PO420 is low catalyst efficiency (possible bad cat), this should not cause your car to stop running. PO135 is saying that the O2 sensor is not heating up for some reason (bad sensor or prob with the wiring. However, i think that even if the O2 sensor does not work your car should start up and run in open loop. I think that the 2 trouble codes are not related to your prob but if the trouble codes are causing the problem it will be PO135 (which has to do with the first O2 sensor, by the cat). I would check for spark and fuel.