p0304 = Number 4 Cylinder Misfire Detected
Faulty spark plug 4
Clogged or faulty fuel injector 4
Faulty ignition coil 4
Fuel injector 4 harness is open or shorted
Fuel injector 4 circuit poor electrical connection
Ignition coil 4 harness is open or shorted
Ignition coil 4 circuit poor electrical connection
Insufficient cylinder 4 compression
Incorrect fuel pressure
Intake air leak
The P0304 code means that the cylinder 4 is misfiring or is randomly misfiring. Start by checking for intake leaks an if no leaks are found the next step is to replace the spark plugs on cylinder 4.
p0102 = Mass or Volume Air Flow Circuit Low Input
Faulty mass air flow sensor
Intake air leaks
Dirty mass air flow sensor
Dirty mass air filter
Mass air flow sensor harness is open or shorted
Mass air flow sensor circuit poor electrical connection
Before replacing the mass air flow sensor, try replacing the air filter and cleaning the air flow sensor with low compress air or mass air flow sensor cleaner.
Reset code and drive vehicle.
If the code comes back, it may be necessary to replaced the mass air flow sensor.
p0154 = O2 Sensor Circuit No Activity Detected Sensor 1 Bank 2
Faulty Front Heated Oxygen Sensor Bank 2
Front Heated Oxygen Sensor Bank 2 harness is open or shorted
Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks
Replacing the Front Heated Oxygen Sensor Bank 2 usually takes care of the problem.
p0113 = Intake Air Temperature Sensor Circuit High
Faulty Intake Air Temperature (IAT) sensor
Dirty air filter
Intake Air Temperature (IAT) sensor harness is open or shorted
Intake Air Temperature (IAT) sensor circuit poor electrical connection
The Intake Air Temperature (IAT) sensor is built into mass air flow sensor or in some vehicles mounted to the air filter duct housing. The sensor detects intake air temperature and transmits a signal to the Engine Control Module (ECM).The temperature sensing unit uses a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to the temperature rise. The Intake Air Temperature signal is used as an input for various systems in the vehicle.
Hope this helps