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Re: 2003 pontiac sunfire GT
When they say "bank," they're referring to cylinder banks 1 or 2. Bank 1 is the passenger's side and has cylinders 1-4 on it. Bank 2 is the driver's side and has cylinders 5-8 on it.
P0171/0174 indicates that the long term fuel trims have reached a maximum (should be somewhere around 30-35%). Fuel trims are how much fuel the PCM adds or subtracts. 0171/0174 indicates that the engine is running lean, meaning that outside air is getting past the mass air sensor. The O2 sensors see this excess air and the PCM responds by cranking up fuel trims to add more fuel for that more air.
Possible solutions include:
In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure
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code p0128 indicates a mechanical fault ( could be the thermostat stuck open)
code p0174 -system too lean -bank2 ===causes --intake /exhaust leak--fuel pressure/pump--injectors--AIR system--hose connection/s
code po171 refers to system too lean bank 1 same as po174 with the HO2S sensor being the culprit. As to all being related . only by way of the o2 sensors
code p0442 is not connected to the first 3 as it is in a different section of the fuel system
Lean bank 1 and bank 2 , and throttle actuator system fault. Check reason for lean codes 1st, vacuum leak(s), air inlet boot and hoses, or low fuel pressure / clogged filter. Repair as needed then clear codes and recheck .
P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
weak coil pack
fowling spark plugs/wires
Low fuel pressure