URD Y Pipe Leak and CEL PO157 (SOLVED)

Sorry for the long post, I put in bold text below my main questions. So, I put on a URD Mark 2 Y pipe in the fall as a way to reroute my exhaust pipe from under the transfer case and put in a rear skid. All was fine until a couple weeks ago when I was wheeling and I threw a check engine light (CEL). After going to Advanced Auto Parts to borrow their scanner, turned out to be a PO157, which is a low voltage condition associated with the O2 sensor (Bank 2 Sensor 2).

In the course of trying to investigate, I've noticed when the car is warming up it drips water from the joints downstream of the secondary O2 sensors (see where I've circled in the stock URD photo below). I've also attached some actual photos of the joints and another showing the puddle on the ground (looks like the puddle that forms from the air conditioning condensate).

One of the possible causes of a PO157 is an exhaust leak, which could cause air to get in and have the O2 sensor sense a lean condition (the sensor sends a 0 to 1 volt signal, close to 1 is rich and close to 0 is lean, hence the low voltage alarm). I strongly suspect that's the issue since the truck only has 17k miles on it and I doubt the O2 sensor is bad. Has anyone had any leaking issues with their URD Mark 2 Y pipe? The joints in question don't come with a gasket; one pipe slips inside the other and then you tighten down a clamp around the joint (a glorified hose clamp setup). Also wondering what is causing the water to form and drip out. I don't see or feel any exhaust air coming out of the the joints, and I've tried cranking down on the clamps.

With regard to the O2 sensor, I'd like to test it to be sure it's not throwing the code, but I need to know which wires are which. The wiring and the harness all look fine and there aren't any broken wires. There are two blacks, one blue and one white. Not sure which are the two for the heater, and which are for the signal and ground wires. I suspect the two black ones are the heater. Can someone confirm which color wires are which for the O2 sensor? Is this covered in either the service manual or wiring diagrams? If so, it's time I downloaded them.

Here's some info I found elsewhere:
P0157 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
P0157 TOYOTA Meaning
The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.
P0157 TOYOTA Possible Causes
What does this mean?

• Faulty Rear Heated Oxygen Sensor Bank 2
• Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
• Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
• Inappropriate fuel pressure
• Faulty fuel injectors
• Intake air leaks may be faulty
• Exhaust gas leaks

Stock URD photo with joints circled


Photos of the leaking joints


Puddle forming on the ground from the leaking joints

 

One of the exhaust components of *perfect* hydrocarbon combustion is water (H2O). Most exhaust systems drip some water until the entire exhaust system has warmed up. This is normal. This is why frequent short trips will do a number on ordinary exhaust systems.
The fault O2 reading may be the result of a leak where the exhaust pipe connects to the manifold (upstream of the circled spots on URD pic). Had this issue with my '06 4.0 V6.

 

So maybe replace the gasket where the Y pipe connects to the header? I used the gasket that came with the Y pipe but maybe I'll pick up some OEM ones from Toyota.

 

To close the loop for any future searches, I installed some defoulers, which are basically a spacer designed to get the O2 sensor out of the direct exhaust airstream. One week and 300+ miles later, and no CEL (knock on wood in case the CEL gods exact punishment on me for daring to suggest I beat a CEL)
http://www.bigdaddiesgarage.com/straight-cel-fix.html

 

I know its an old thread, but was curious if this fixed your issue for good? I am having the same issue with ucon, urd spec-u headers and urd y-pipe.

Did you only install the defouler in the rear o2 for bank 2 (driver side)? Or in each o2 sensor?

Thanks in advance