Position of oxygen sensors

Four .
Heated Oxygen Sensor (HO2S Bank 1 Position 1)
Located in RH front pipe of the exhaust catalytic converter
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Engine Controls Connector End Views in Engine Controls
Heated Oxygen Sensor (HO2S Bank 1 Position 2)
Located in RH rear pipe of the exhaust catalytic converter
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Engine Controls Connector End Views in Engine Controls
Heated Oxygen Sensor (HO2S Bank 2 Position 1)
Located in LH front pipe of the exhaust catalytic converter
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Engine Controls Connector End Views in Engine Controls
Heated Oxygen Sensor (HO2S Bank 2 Position 2)
Located in LH rear pipe of the exhaust catalytic converter

You have to remove the sensor with 7/8 wrench or a oxygen sensor socket. Or loosen the exhaust pipe at the manifold so the pipe will fall out of the way

Fig. Component Location Chart-2000 MPV

1 PCM 2 Mass air flow (MAF)/intake air temperature (IAT) sensor 3 Throttle position (TP) sensor 4 Fuel tank pressure sensor 5 Engine coolant temperature (ECT) sensor 6 Crankshaft position (CKP) sensor 7 Camshaft position (CMP) sensor 8 Knock sensor 9 Heated oxygen sensor (HO2S) (front, LH) 10 Heated oxygen sensor (HO2S) (front, RH) 11 Heated oxygen sensor (HO2S) (rear, LH) 12 Heated oxygen sensor (HO2S) (rear, RH) 13 EGR boost sensor 14 Power steering pressure (PSP) switch 15 Main relay


Fig. Component Location Chart-2001 MPV

1 PCM 2 Mass air flow (MAF)/Intake air temperature (IAT) sensor 3 Throttle position (TP) sensor 4 Engine coolant temperature (ECT) sensor 5 Crankshaft position (CKP) sensor 6 Camshaft position (CMP) sensor 7 Knock sensor 8 Heated oxygen sensor (HO2S) (front, LH) 9 Heated oxygen sensor (HO2S) (front, RH) 10 Heated oxygen sensor (HO2S) (rear, LH)* 11 Heated oxygen sensor (HO2S) (rear, RH)* 12 EGR boost sensor


Fig. Component Location Chart- 2002-06 MPV

Not just a faulty catalytic converter will trigger this code. Many other issues can trigger this code.

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Delayed spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible solutions:

• Check for exhaust leaks at the manifold, pipes, catalytic converter.
• Replace Coolant Temperature Sensor
  
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2)
• Replace the catalytic converter
• Have timing adjusted
  

A muffler shop should be able to replace just the converter

P0157 Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)

I would try replacing the Oxygen sensor, then clear the code.

The O2 sensor would be the after the catalytic converter ( sensor 2) on the exhaust pipe of the number 2 cylinder uses ( bank 2).

Try replacing the gas tank cover. Seriously. If that does not work, it could be the clutch sensor.

it means the oxygen sensor closest to the exhaust man. is bad , replace

2002 PCED OBDII-Villager SECTION 1: Description and Operation Catalyst and Exhaust System Overview The catalytic converter and exhaust system work together to control the release of harmful engine exhaust emissions into the atmosphere. The engine exhaust gas consists mainly of nitrogen, carbon dioxide and water vapor. However, it also contains carbon monoxide, oxides of nitrogen, hydrogen, and various unburned hydrocarbons. Carbon monoxide, oxides of nitrogen, and hydrocarbons are major air pollutants, and emission into the atmosphere must be controlled.
The exhaust system consists of an exhaust manifold combined with a pre-catalytic converter, upstream heated oxygen sensor (HO2S11), (located just in front of the pre-catalytic converter), three way catalytic converter (TWC), downstream heated oxygen sensor (HO2S12) (located in front of the TWC), a muffler and an exhaust tailpipe.
Heated Oxygen Sensors The Villager is equipped with both upstream and downstream heated oxygen sensors (HO2S) (Figure 1). The upstream heated oxygen sensor (HO2S11) is used to control engine fuel flow. The sensor detects the concentration of oxygen in the exhaust gas and sends a signal to the powertrain control module (PCM). In a rich condition, the HO2S will output a voltage of 0.6 volts or greater, and in a lean condition a voltage of 0.4 volts or less will be output.
The downstream heated oxygen sensor (HO2S12) is used primarily for monitoring the efficiency of the catalytic converter system. The HO2S12 works in a similar way to the HO2S11 but only indicates to the PCM that the catalyst is functioning properly. In the event that the HO2S11 fails, fuel control will be switched over to the HO2S12 and the malfunction indicator lamp (MIL) will be illuminated. This allows the vehicle to operate with fewer emissions, even with a sensor failure.
Figure 1: Typical Heated Oxygen Sensor (HO2S)

The first sensor closest to the exhaust manifold is for the air to fuel ratio. The second one if it has one will be further downstream and checks to see if exhaust is plugged.

Is your car running right especially at idle????