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Have a 2014 2500 Promaster. Need to replace the o2 sensor bank one. Anybody know where this is located?
 

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It is for the rear set of cylinders and should be between the manifold and the catalytic converter assuming it is the upstream sensor that needs replacement. I’d just get the front of the van up on ramps and slide under with my flash light and my O2 sensor socket and ratchet and the new sensor with me! It should be obvious.
 

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No, upstream means BEFORE the catalytic converter and downstream means AFTER it. Bank 1 is the rear set of cylinders Bank 2 is the front set. How do you know it needs replacing?
 

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Replaced the motor. The head blew and oil pump went. Couple hours after motor replaced it threw the code for bank 1 o2 sensor. These vans have 1 converter or 2?
 

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So much basic info to cover! The van has 4 o2 sensors, 2 in each cat. But it is highly unlikely you need one. There are dozens of conditions that cause an o2 sensor code (P0171?) and none of them mean a bad sensor. Lean, rich, vacume leak, injectors, fuel pump, thermostat, alternator...any of those can/will trip that code. Get it to a mechanic who can diagnose it BEFORE you start shotgunning parts.

If you just can't keep your hands off of it, I would suggest swapping both front o2 sensors with both rear ones, and see if the code moves. This would cost nothing and rule out anything and everything related to the sensors. The front cat is easy to get out, the rear cat requires dropping the crossover pipe. But if the engine was just swapped all of that was apart, so you probably wont have much trouble with the bolts. Whole job might take you a couple hours. You might be able to get the sensors out without removing the cats, but it's pretty tight, especially the rear ones.

From personal experience, I know that all 4 sensors are identical, and the cost about $70 each for OEM. Don't even consider putting in the $30 autozone ones, they will fail/ruin your life in short order.

Let us know what happens.
 

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It was a shop that diagnosed the o2 sensor. Today I located this sensor. It's right above the cat on the back side. My wrench was too big for the area to get a solid bite on it. I may find a shop to do it at minimal cost. I replaced the fan assembly unit today. Removed & installed new from the bottom.
 

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Fan assembly isn't that bad of a job, especially once you've done it once. It looks crazy at first, but if you remove the grill (both the outer and inner parts) and then you remove the crosspiece (the crossmember the surge tank is attached to) then the fans easily come out from the top. Once the fan is out, then other jobs become a piece of cake, namely the alternator, a/c compressor, all the hoses and heater hoses. Indeed, getting the intake manifold off is super easy once the crossmember is off.

Next time I do this, I'd like to make a video and put it on youtube. At first glance, the promaster looks like a PITA to service, but it really isn't.
 

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I didn't do all that to do the fan. I took it out the bottom in couple seconds. Once you unhook the 6 connectors that are plugged in then it's just releasing those 2 top brackets and push up a little and then pull it out from the bottom. This O2 bank 1 sensor 1 is a hard one. At the top of the cat so you can only feel to where you need to put the wrench. I can only fit one arm up there all the way but need a shorter wrench. Shop wants $100 to do.
 

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Wonder if the original poster ended up replacing catalytic converters...
I had similar scenario, replaced motor and after 100 miles or so got a P0420.

Anyone ever replace the rear catalytic converter DIY style?
The front is pretty straightforward but the rear Cat two bolts attaching to the manifold are very difficult to access.
 

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They arent too bad. The trick is to do it from over the top of the engine with an open ended wrench. Save time? Have a friend put the wrench on the bolt from the bottom, then you put the force on it from the top.
 

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Wonder if the original poster ended up replacing catalytic converters...
I had similar scenario, replaced motor and after 100 miles or so got a P0420.

Anyone ever replace the rear catalytic converter DIY style?
The front is pretty straightforward but the rear Cat two bolts attaching to the manifold are very difficult to access.
I definitely didn't DIY it but I did have to replace both catalytic converters before hitting 15k miles. I learned there's a 7-year, 70k mile federally mandated warranty on all emissions components, which the dealer forgot to mention until I brought it up.
 

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What caused the cats to go bad after so few miles?
 

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What caused the cats to go bad after so few miles?
I wish I knew! I asked the tech when they replaced it and just got a shrug.

I bought the van off auction (3 years old with 14k miles, clean title...though you'd never know it by looking). It was owned by an electrician in NYC before me.
 

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I didn't think cats could go bad with a modern engine these days due to ECU/fuel injection ensuring properly air/fuel ratio (too much unburnt gas is hard on a cat) and gas now being unleaded (lead will destroy a cat quickly).
 

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I didn't think cats could go bad with a modern engine these days due to ECU/fuel injection ensuring properly air/fuel ratio (too much unburnt gas is hard on a cat) and gas now being unleaded (lead will destroy a cat quickly).
Not so. Our vans have 2 o2 sensors per cat. The upstream one lives at the inlet of the cat, and if the sensor goes bad or the wiring to it is bad, it will read wrong and the engine will run rich, destroying the cat pretty quickly. If the engine runs rich for other reasons (bad ignition, leaky fuel injector, low compression) same story.

They downstream sensor reads what’s coming out of the cat, and compared that to the input sensor to determine the health of the cat. The downstream sensors light the light of they go bad, but otherwise affect nothing.
 
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Not so. Our vans have 2 o2 sensors per cat. The upstream one lives at the inlet of the cat, and if the sensor goes bad or the wiring to it is bad, it will read wrong and the engine will run rich, destroying the cat pretty quickly. If the engine runs rich for other reasons (bad ignition, leaky fuel injector, low compression) same story.
Interesting! I guess that is a vulnerability with the sensor system.
 

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The real problem with o2 sensors is misdiagnosis. Vast numbers of situations can cause too much or too little fuel to get burned, which shows up as a P0420 code. The average person reads that, goes to autozone and buys crappy cheap o2 sensors, and replaces them, and still has the code.
Not for nuthin’ but I have 3 vans, thus 12 o2 sensors. The vans have 1.5+ million miles. 11 of the o2 sensors are original equipment.
 
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