PO141 After Over the Frame Exhaust

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A

AlaskanLX450

10 Year
Joined
Jan 26, 2013
Threads
25
Messages
186
Location
Anchorage Alaska
1996 LX450, 172k miles

Finally got my exhaust routed over the frame!!! I've been saving up for it for a while, gathering parts and pieces to make it go quicker, soo happy with the sound and throttle response!!

But... after driving it for a couple days, it flipped a Rear O2 Sensor code PO141. I have the Magnaflow Y-Pipe and front cat assembly, we deleted the rear cat and routed it over the frame. We installed a new O2 sensor flange almost exactly where the factory location was, and installed a new Denso OEM replacement sensor.
Truck runs excellent, wonderful throttle response and butt dyno tells me its pulling a touch better than it was before. Just that orange light on the dash...

The only thing I can think is that the sensor might be too far away from the cat now? The only scanner I have used is one of the OReilly ones, I don't have voltage reference numbers right now.

I would really like to go back to the random EGR code and not this O2 code... Any help is appreciated!!!
 
My non-expert opinion:

From what I have read having one CAT should not cause a problem.

Might be too far from the CAT. O2 sensors need to be at the right temperature to function, hence why some are heated.

Did you replace the upstream one at the same time? Since they are reading a differential between the two both should be done at once.
 
Pascoscout said:
My non-expert opinion:

From what I have read having one CAT should not cause a problem.

Might be too far from the CAT. O2 sensors need to be at the right temperature to function, hence why some are heated.

Did you replace the upstream one at the same time? Since they are reading a differential between the two both should be done at once.
Click to expand...

The upstream sensor was replaced about two years ago when I replaced the factory Y-pipe with the Magnaflow part. I intended to do the rear modification earlier but finances got tight and it was put on hold.

The new rear sensor is in roughly the same area as the factory one, but there is about a foot of pipe where one of the cats used to be now. I really like the location, its very well shielded for off road use. I'm gonna be kinda bummed if I have to relocate it...

Thanks!!!
 
P0141 pertains to the heater circuit of the rear O2 sensor. Essentially, battery power is supplied to the heater circuit via the EFI relay and is grounded by the ECM. The ECM analyzes the return voltage and if it doesn't like what it sees it sets that code. Unfortunately the diagnostic procedure given in the FSM is pretty vague. First you need to check for a open/shorted circuit within the sensor between cavities 1 and 2 (yellow/red and orange) then check for battery power at the yellow/red wire at the harness connector with the key on and continuity from the orange wire at the harness connector to the ECM connector(pin7 on connector 6), but if the problem only occurred after the sensor was replaced then the new sensor would be highly suspect.
 
VehiculousFJ said:
Any update on this? I experienced the same issue once I replaced my downpipe with the magnaflow and deleted the cat.
Click to expand...

I haven't done too much besides clear the code and see how long before it came back and then wheel the crap out of it since summer in Alaska is short! :beer::steer:

My research has lead me to needing to check voltages and verify the circuit for the heater is working correctly. The sensor is functioning, the truck runs flawless. If I don't get a chance to spend much time with a voltage meter, I will try throwing a cheapy sensor in it and keep my fingers crossed its just a bad heater element in the sensor. The one I installed was technically new, but had been rattling around my toolbox for almost 2 years before I actually installed it...

If I remember.... I PROMISE to update when this is resolved.. :banana:
 
Could you post up some pics of your exhaust setup and your rear sensor location. I'm building a system too. Thanks!
 
I only have one cat on mine as well. I once saw that code after reseting the ecu. I did the relearn process and it went away.

Do you have any exhaust leaks? Check upstream of the o2 sensors.
 
ccslider said:
I only have one cat on mine as well. I once saw that code after reseting the ecu. I did the relearn process and it went away.

Do you have any exhaust leaks? Check upstream of the o2 sensors.
Click to expand...
No upstream leaks, OEM toyota gaskets at the manifolds and one piece Magnaflow Y-pipe with cat all the way to the bolted on cat back system we put on. What is this relearn procedure you speak of? I've cleared the codes a couple times, light comes back on within 3 ignition cycles.
 
AlaskanLX450 said:
I haven't done too much besides clear the code and see how long before it came back and then wheel the crap out of it since summer in Alaska is short! :beer::steer:

My research has lead me to needing to check voltages and verify the circuit for the heater is working correctly. The sensor is functioning, the truck runs flawless. If I don't get a chance to spend much time with a voltage meter, I will try throwing a cheapy sensor in it and keep my fingers crossed its just a bad heater element in the sensor. The one I installed was technically new, but had been rattling around my toolbox for almost 2 years before I actually installed it...

If I remember.... I PROMISE to update when this is resolved.. :banana:
Click to expand...
AlaskanLX450 said:
Its a bit muddy from this weekends fun run... I will get it cleaned up and get some pics!!
Click to expand...

Calling you out on your promise! ;) I'm curious if this was resolved and also interested in the pictures of how you routed the exhaust. Thanks!
 
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