You have 1999 dodge truck 5 2 1500 ram and you used a hand held diagnostic reader the code read 0133 which is genric It seems to be running rich o2 sensor would say it is?

Code P0133 (or 0133, depending on the reader) is indeed a generic OBD-II code that points to a problem with the oxygen (O2) sensor circuit for bank 1, sensor 1. Bank 1 refers to the side of the engine containing cylinder #1, and sensor 1 is the upstream O2 sensor (located before the catalytic converter). A malfunctioning sensor *can* cause a rich condition (too much fuel), but it's not the only possible cause.

While a faulty O2 sensor is a strong suspect given the code, "running rich" is a symptom, not the problem itself. The O2 sensor's job is to tell the engine's computer (PCM or ECM) how much oxygen is in the exhaust. If the sensor is bad, the computer may be getting inaccurate readings, leading it to add too much fuel. However, other issues can also cause a rich condition and trigger this code:

* Faulty O2 Sensor: This is the most likely culprit. The sensor might be failing, shorting, or just plain worn out. Replacement is relatively inexpensive and straightforward.

* Vacuum Leaks: A leak in the intake manifold or vacuum lines can cause a lean condition (too little fuel), but the computer may overcompensate and end up running rich. This often results in rough idling and poor fuel economy.

* Fuel Injectors: A stuck-open or leaking fuel injector will constantly inject fuel, leading to a rich condition. This can cause rough running and black smoke from the exhaust.

* Mass Airflow (MAF) Sensor: The MAF sensor measures the amount of air entering the engine. If it's malfunctioning and reporting incorrect values, the computer will add the wrong amount of fuel.

* Fuel Pressure Regulator: A faulty fuel pressure regulator might be delivering too much fuel pressure to the injectors.

Before replacing the O2 sensor:

1. Check for vacuum leaks: Visually inspect all vacuum lines and the intake manifold for cracks or loose connections. You might need a vacuum gauge to accurately test for leaks.

2. Check the MAF sensor: This usually involves cleaning it with MAF sensor cleaner (following the instructions carefully) or replacing it if cleaning doesn't resolve the issue.

3. Inspect wiring and connectors: Ensure the wiring to the O2 sensor is intact and the connectors are clean and secure. A loose or corroded connection can cause intermittent problems and trigger the code.

If you've checked those and still have the P0133 code, then replacing the upstream O2 sensor is the next logical step. Make sure you get an O2 sensor that's the correct type for your 1999 Dodge Ram 1500 5.2L. After replacement, clear the code with your handheld scanner and test drive the truck to see if the code returns. If it does, then you need to investigate the other possible causes listed above.