Question

1998 Ford Explorer 4.0L OHV, what are these codes P0136 and P0305?

Answer 1

P0136 is the O2 circuit which monitors the fuel/air mix of your converter..Bank one, sensor two

P0305 is a misfire on Cylinder 5.(304 would be cylinder 4) so the first thing you do is check the spark plug, then the spark plug wire, if your misfire remains you may have a bad coil pack. Then from there you consider a faulty fuel injector for that cylinder....Then finally a compression check if all else fails.

Answer 2

P0136 FORD - Heated Oxygen Sensor Circuit Malfunction Bank 1 Sensor 2
Read more: https://www.autocodes.com/p0136_ford.html

P0305 FORD - Cylinder 5 Misfire Detected
Read more: https://www.autocodes.com/p0305_ford.html