My engine light stay on and there are four codes. I changed the bank 1 sensor 2 and a new gas cap and also theegr oxygen sensor but the engine light is still on. any suggestion?

code p 0171 refers to system too lean bank 1===causes ---intake /exhaust leak---AIR system---MAF/VAF sensor/s---fuel pressure/ pump---injector/s---heated oxygen sensor (HO2S) the one in the exhaust manifold for bank 1 nearest the firewall

I think you need Bosch for that vehicle. here is a rundown how it helps


Every automobile manufactured after the 1980s is equipped with an oxygen sensor. This component measures the ratio of air and gasoline in the engine and feeds the data to the vehicle's computer. With an oxygen sensor, your engine runs more efficiently and produces as few emissions as possible. If your car's running with a busted oxygen sensor, you better get a new one before your engine's efficiency takes a nosedive and your gas bills skyrocket. We know that looking for the right replacement oxygen sensor can be very tricky, that's why we've come up with a guide for you to keep in mind when shopping for a new oxygen sensor.
Which oxygen sensor should you buy?
There are a lot of questions about which oxygen sensor to replace. In fact, failures are common among cars especially when the wrong sensor is installed. With today's automobiles equipped with at least two, or even three or four oxygen sensors, it can be very confusing as to which one is not working correctly. There are probably a lot of sensor codes to choose from and here's a tip to help you sense the right oxygen sensor.
Oxygen sensors are always numbered this way:
Bank 1 Sensor 1
Bank 2 Sensor 1
Bank 1 Sensor 2
Bank 2 Sensor 2
Other manufacturers code their oxygen sensors this way, which is why it can sometimes be very confusing. However, they all mean the same:
Sensor 1/1 or O2s 1/1
Sensor 2/1 or O2s 2/1
Sensor 1/2 or O2s 1/2
Sensor 2/2 or O2s 2/2
Now here's a detailed list to know which is which:

• Bank 1 is located at the side of the engine where cylinder #1 is found as well.
• Bank 2 is on the opposite side of Bank 1.
• On a 4-cylinder engine, there is only one bank that's called Bank 1.
• Sensor 1 is the upstream sensor located before the catalytic converter.
• Sensor 2 is the downstream sensor located after the catalytic converter.
• Sensor 3 is the only downstream sensor in situations where there are two sensors before the catalytic converter and only one after it. On other cars, this is read as Bank 1 Sensor 3.

With these detailed tips on how to sense the right oxygen sensor, you'd be sure to buy the right replacement part at your store. Be sure to purchase one from a trusted brand to avoid any complications you might experience with ones that are bought from local junkyards BEST OF LUCK

code p0054 is
Possible causes - Faulty Heated Oxygen Sensor Bank 1 Sensor 2
- Heated Oxygen Sensor Bank 1 Sensor 2 harness is open or shorted
- Heated Oxygen Sensor Bank 1 Sensor 2 circuit poor electrical connection
When is the code detected?Heater current requirements too low or high in the heated oxygen sensor (HO2S) heater control circuit Symptoms- Engine Light ON (or Service Engine Soon Warning Light)
code p0141 is O2sensor heater circuit malfunction( bank one sensor 2)
there is chance that wire from that sensor is touching,part of your exhaust system,and either is open or shorting to ground

code p0036
036 - HO2S Heater Control Circuit Bank 1 sensor 2check the wire from the sensor for the sign cut or melting,and change the sensor

P0152 P0152 - O2 Sensor Circuit High Voltage Bank 2 Sensor 1Possible causes - Faulty Front Heated Oxygen Sensor Bank 2
- Intake air leaks may be faulty
- Exhaust gas leaks
- 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
eplacing the Front Heated Oxygen Sensor Bank 2 usually takes care of the problem
Symptoms- Engine Light ON (or Service Engine Soon Warning Light)
- High Fuel Consumption
- Excessive Smoke from Exhaust P0152 Description The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

P0442 FORD - Evaporative Emission System Leak Detected Small Leak

Possible causes- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking
P0136 - O2 Sensor Circuit Malfunction Bank 1 Sensor 2
Possible causes- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
- Faulty Rear Heated Oxygen Sensor Bank 1
- Inappropriate fuel pressure
- Faulty fuel injectors
- Intake air leaks may be faulty
- Exhaust gas leaks

P0141 FORD - O2 Heater Circuit Bank 1 Sensor 2

Possible causes- Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit fuse
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit open shorted to ground
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit poor electrical connection
- Faulty Engine Control Module (ECM)

These codes, po 138 bank 1 sensor 2 shorted to voltage and code po158 means bank 2 sensor two shorted to voltage. these are the two rear oxygen sensors in the exhaust system. there two up frt and two in the rear, check the wiring on the two rear sensors, make sure that the wiring is not cut or stuck between metal. if the wiring is good then replace both rear sensors, when you get them ask for the left and right after the cat sensors. or bk1 s2 and bk2s2. after replacing them reset the computer. go to an auto parts sotre or if you have a code reader you can do it. hope this helps good day.

code p 0138 refers to 2 items
1--heated oxygen sensor(HO2S) 2 bank 1--high voltage ==causes --wiring short to positive --HO2S---ECM
2--oxygen sensor (O2S) 2 bank 1--high voltage ===causes wiring short to positive ---ECM
code p 0139 refers to 2 items
1--- heated oxygen sensor (HO2S) 2 bank 1--slow response ===causes --heating inoperative --wiring--ECM
2--oxygen sensor (o2S) 2 bank 1 slow response ===causes --wiring --- O2S

heated oxygen sensors9HO2S) are in the exhaust manifold before the cat converter
Oxygen sensors (O2S) are after the cat converter
it is indicated that the HO2S is faulty-
check the wiring and /or replace both sensors

The error that I'm showing for error code P1133 is 
P1133 Heated Oxygen Sensor (HO2S) insufficient switching bank 1 sensor 1(Rear Bank).  I would suggest having both of your Oxygen Sensors replaced if you haven't already had that done.  Hope this helps.  Thanks for an honest rating and for using FixYa.

There are fuses for oxygen sensor heaters. Check for 12 volts to the sensor with key on.