Is it the furthest back on the exhaust?

It's right after the Cat, isn't it?

 

The rear (firewall side of the engine has cylinder #1 so that is bank 1 and the front (radiator) side is bank 2. The #1 sensors are the closest to the engine in the exhaust manifold. FROM: http://www.justanswer.com/mazda/7q5w...e-v6-want.html
Yes Sensor 2 is right after the pre-cat.

Having Cat problems like this means you should try this first:

 

Thanks - I'll give it a look tomorrow.

I didn't dump lacquer thinner in my tank, but I did add Seafoam.

 

Did the repair - now how do I reset or clear the check engine light?

 

remove the negative terminal on the battery (this should have been done while doing repais). Followed by a few brake applications and honking of horn to make sure all active current is gone. Wait 10 minutes.
Re-hook-up negative terminal.
Re-start vehicle and let idle for 10 minutes. Re-learning has begun and will continue for 50-100 miles.

 

Thanks

 

I replaced the Sensor in question (bank 1, sensor 2). Cleared the check engine light, and drove it for 20 or so miles. CE light came back on as I arrived home and it gives me the same code - P0136.

What's next?

 

Essentially the same as P0137, a P0136 code refers to the second oxygen sensor on Bank 1. The O2 oxygen sensor produces a voltage between .1 mV and .9 mV. The ECM monitors O2 sensor voltage and determines if exhaust is lean or rich. O2 sensor voltage is high when exhaust is rich and low when exhaust is lean. The ECM monitors this voltage and increases or decreases fuel injector pulsewidth according to engine fuel/air ratio. If the ECM detects low HO2Sensor voltage for an extended period, it will set P0136 Conditions required to set: HO2 sensor voltage is low for longer than 2 minutes (minutes depend on model of vehicle. Could be up to 4 minutes)

Symptoms There may be no visible symptoms to the driver. Poor fuel mileage, possible misfire, depending on O2 sensor position when sticking. Causes A code P0136 may mean that one or more of the following has happened: Faulty O2 sensor leak in exhaust close to O2 sensor, Short to voltage on O2 signal circuit, Open in circuit resistance caused by corrosion in connector

Possible Solutions Replace the second oxygen sensor on bank 1,
Repair open or short in signal circuit,
Clean corrosion from connector

Read more at: OBD-II Trouble Code: P0136 Oxygen O2 Sensor Circuit Low Voltage (Bank1, Sensor2)
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Common Problems That Trigger the P0130 and P0136 Code

Defective Oxygen Sensor/Air Fuel Ratio Sensor
Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater circuit
Exhaust System Leak
Intake Air System leak (including vacuum leaks)
Low Fuel Pressure
Defective Engine Coolant Temperature Sensor
Defective sensor wiring and/or circuit problem
PCM software needs to be updated
Defective PCM

FROM: OBD II Code P0130 and P0136

 

Wow. Thanks for the in-depth reply. I will definitely try and put that information to use.

I recently bought an ELM327 Bluetooth device and downloaded Torque onto my phone, and it looks like a pretty decent diagnostic tool. Of course the information it provides is a foreign language to me, but I'll work on that part.

I appreciate the help.

 

I would really try the lacquer thinner!
I know you did seafoam!