I have a 1997 Bravada that has a bad oxygen censor and a bad caytalytic converter. Would both of these problems cause a misfire, and , wich sensor is in bank 2

The PO420 code is a generic code indicating a problem with the catalytic converter system efficiency below threshold. This issue can be caused by several factors, including:

1. A clogged or failing catalytic converter
2. An exhaust leak before the catalytic converter
3. A malfunctioning oxygen sensor
4. Fuel system issues, such as a clogged fuel injector
5. Engine misfire
6. A damaged or failing ignition system
7. A vacuum leak

Here are the steps you can take to diagnose and fix the issue:

1. Check the catalytic converter: If the converter is clogged, it may need to be replaced.
2. Examine the exhaust system for leaks: Leaks before the catalytic converter can reduce its efficiency. If a leak is found, it should be repaired.
3. Replace the oxygen sensor: If the oxygen sensor is malfunctioning, it can cause the engine to run too rich or too lean, which can affect the catalytic converter.
4. Check the fuel system: Clogged fuel injectors can cause a lean fuel mixture, which can harm the catalytic converter. Have the fuel system checked and cleaned as necessary.
5. Repair any engine misfires: An engine misfire can damage the catalytic converter over time. Fix the misfire and see if the code returns.
6. Check the ignition system: A faulty ignition system can cause a misfire and damage the catalytic converter. Have the ignition system checked and repaired as needed.
7. Find and fix any vacuum leaks: Vacuum leaks can cause a lean fuel mixture and damage the catalytic converter.

It's best to have a mechanic diagnose the problem and perform the necessary repairs, as some of these repairs can be complicated and require specialized tools.

code p 0141 refers to heated oxygen sensor (HO2S) 2 bank 1--heater control--circuit malfunction===causes --wiring---HO2S--- ECM
code p 0144 refers to heated oxygen sensor(HO2S) 3 bank 1--high voltage ===causes wiring short to positive ---HO2S---ECM
also refers to oxygen sensor(O2S) 3 bank 1--high voltage ===causes wiring short to positive---O2S-- ECM
HO2S sensors are the units in the exhaust manifolds or before the cat converters
O2 sensors are after the cat converter
two completely different operations
use the special tool for sensors as the wires are easily damaged from the wrong tool use
as for misfiring you will get a P0300 (0300,0301,0302,0303 etc) depending on which cylinders are misfiring
when checking for misfiring the injectors , (blocked or not firing) are as important as plugs and wires
If the misfiring continues after sensor replacement , replace the ECM with a known good one as it is common to all fault codes and misfiring

• Inefficient Catalytic Converter(s)
• Defective Front or Rear Oxygen Sensor(s)
• Misfiring engines

usually this code is followed by another number 1-4 or 1-6 or 1-8 depending on how many cylinders your vehicle has ,, what the code you got is a basic P0300 Random/Multiple Cylinder Misfire Detected A code P0300 may mean that one or more of the following has happened:

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer
• I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
  Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck ope
  

P0304 Code - Cylinder #4 Misfire Detected
A P0304 code means that the the car's computer has detected that one of the engine's cylinders is not firing properly. In this case it's cylinder #4.

Symptoms may include:
* the engine may be harder to start
* the engine may stumble / stumble, and/or hesitate
* other symptoms may also be present

Causes: A code P0304 may mean that one or more of the following has happened:
* Faulty spark plug or wire
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector
* Burned exhaust valve
* Faulty catalytic converter(s)
* Running out of fuel
* Poor compression
* Defective computer

Possible Solutions:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Hope helps.

Have you changed the spark plug wires? This is the most common cause of a misfire. After changing the wires, I would then have the Timing checked and a new timing belt installed. If this doesn't fix the problem, you may have a Crankshaft Position Sensor or Camshaft Position Sensor failing. If this doesn't fix the problem, have your fuel pressure tested.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

the engine miss fire can cause the other codes to set. you need to repair the miss fire and clear all codes after the miss is repaired then see if the 02 sensor codes return. the miss fire is probably a bad spark plug wire a good tune-up should take care of it ........HAVE A GREAT DAY

For 1997 Mercury Grand Marquis 4.6L SFI 8cyl the Oxygen Sensor is located: Under vehicle, passenger side, below seating area, mounted in exhaust pipe in rear of catalytic converter

Application: Number three


Hope helps (remember to rate this).

PO135 = Upstream Heated Oxygen Sensor Heater (HTR 11) circuit (Bank #1)

P1131 = Lack of upstream Heated Oxygen Sensor (HO2S 11) switch, sensor indicates lean (Bank #1)

P0305 = Cylinder #5 Misfire detected

It looks like you have two separate issues happening. Bank 1 would be the left side of the engine if you were standing in front of the truck looking at the engine. The "upstream" oxygen sensor will be on the exhaust pipe coming from the bank one side of the truck IN FRONT of the catalytic converter. From the codes, it appears that the upstream sensor has gone bad, but the oxygen sensor behind the catalytic converter, or "down stream" is fine.

The misfire on cylinder 5 on the right side of the engine, 2nd one from the front, could be something as simple as a fouled spark plug or a coil malfunction.

To identify if it is a bad coil, swap the #5 cylinder coil with another coil, and see if the misfire follows the relocated coil.

I have a 1997 Mercury Villager with many miles. We get poor gas mileage. The check engine light is on. I want to replace the 02 sensor but cannot locate it on the engine. Is there a link with photo of physical location of the sensor and what are the steps to replace it?