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I recently removed the catalytic converter on my sister's 2001 Rav4 for some diagnostic work prompted by a steady, long-term check engine light (MIL). There were no major performance issues, though there was a little bit of an occasional rough idle, which would happen after quickly decelerating to a complete stop (ie, to a stop light, or to the end of a freeway ramp). The Rav is a California-emissions 4.2, is still in California, and was due for a required emissions inspection which it would have failed due to the codes alone, and possibly other issues they might indicate. I checked the codes, and the following were shown:


P0174, System Too Lean, Bank 2.
P0171, System Too Lean, Bank 1.
P0420, Catalyst System Efficiency Below Threshold, Bank 1
P0430, Catalyst System Efficiency Below Threshold, Bank 2​


This first of these, P0174, is usually most easily remedied by simply cleaning the Mass Air Flow sensor (MAF). This is an easy fix which is described in another post here:



The other codes are associated with failure of either the catalytic converter itself or one of the four sensors in it. The 4.2 catalytic converter is a TWC, or three-way converter, type unit. There are two banks, each of which has two sensors. The top sensors on each bank are Air-Fuel Ratio sensors (A/F sensors), and the bottom sensors are Oxygen sensors, but OBD II codes will number then all as "oxygen sensors" and designate them by location. For example, the "Bank 1" A/F sensor may be called "Oxygen Sensor 1, Bank 1" on the OBD II scanner, and the A/F sensor on "Bank 2" may be called "Oxygen Sensor 1, Bank 2". Here are the Bank and Sensor location numbers:




The codes are helpful enough to locate the problem, but also vague in that they could lead you to replace more components than needed, such as a total catalytic converter replacement when the cause could have been just a single sensor or a sensor pair in a single bank.

This post shows instructions and pictures for removing the catalytic converter and the sensors. It is not a difficult job, and you can do it yourself to save a lot of money.


TOOLS:

12-mm closed-end wrench
12-mm deep socket
14-mm socket
22-mm Oxygen Sensor Socket
ratchet wrench
breaker bar (probably)
hammer (maybe)
PB Blaster lubricating spray
anti-seize
razor blade (for scraping carbon build-up on manifold)


SUPPLIES:

Gaskets: there are two gaskets on the catalytic converter -- one on the manifold-converter mating surface (top), and one on the converter-exhaust pipe mating surface (bottom). The manifold gasket is listed as possibly re-usable, and the exhaust pipe gasket is listed as "non-reusable" in the FSM. Either of these gaskets can fail and require replacement. If you find that your manifold stay brackets are missing (see #5 below), you should definitely replace the exhaust pipe gasket, as you will see how worn out it will be when you compare it to a new gasket.


The Toyota part numbers are:


"Gasket, Exhaust Manifold to Head", 17173-28010, about $22 on localpartsshop.com.
"Gasket, Exhaust Pipe", 17451-74040, about $32.​

This job was done on Labor Day, so I didn't have access to a Toyota dealer. Autozone had both gaskets by Felpro, and they were much less expensive. The Felpro exhaust gasket was very similar to the OEM gasket. But the manifold gasket was quite different from the OEM in that the Toyota manifold gasket is made of two pieces of metal that are pinched together in a few places, while the Felpro gasket is a thicker, single sheet composite material. While different, the Felpro gasket seemed to be a good quality, was successfully installed, and does not appear to be leaking in any way.

Felpro Exhaust Manifold Gasket, MS-94140-1 (here)

Felpro Exhaust Flange Gasket, 61106 (here)


Catalytic Converter: an OEM converter is the best option, but also the most expensive. Aftermarket converters are available and are much less expensive (usually half the price of an OEM), but understand that some of the aftermarket converters are known to prompt re-curring Check Engine lights, even if they are functioning well. The check engine light might cause your car to be failed during emissions inspections, depending on your location.

In my case, I was able to use the converter from my other sister's Rav4 as a test converter before buying anything new, and this proved to be very useful as it turned out that the suspect converter was NOT damaged after all. The other Rav was set to be scrapped (long story), and so we were using parts from it to fix the "good" Rav. This is unusual, though, because other than this unique situation where I had access to two privately owned Rav4's with interchangeable parts, you are not going to be able to obtain a "used" catalytic converter in the US. Environmental restrictions require that all "used" converters be sold only as "scrap", whether they work or not (this is stupid in my opinion, but nobody asked me). I *think* that an individual vehicle owner can legally chose to buy a "scrap" converter and personally install it on their personal vehicle, but I may be wrong. I know shops cannot and will not install used or "scrap" converters, or trade in them in any way. So effectively I think there is no market for used converters in the US.


STEPS:
Note: This DIY adds pictures and was helped by a very helpful previous report from jabawaki (here). I recommend that you remove the main heat shield (the one that you see right when you open the hood, which has a little crossed-out hand image on it) the night before you plan to do this job, and spray the nuts which fasten the converter to the manifold with PB Blaster, as well as the spring bolts under the converter which fasten it to the exhaust pipe. These California Ravs didn't have any serious rust, but I think most Ravs would. All of these bolts get very hot during operation and are especially prone to sticking. To do this, just do steps #1 through 4# the night before.


1.) Disconnect the negative terminal on the battery.

2.) Disconnect the electrical connections on the four sensors. There are two on each side -- label both ends of the connections to make re-installation quick and easy. Reach down the length of each wire to each sensor, and remove the wires from the plastic clips. Your clips may break in doing this: don't worry, just remember where the clips fastened and loop a zip-tie through those spots and around the wire when you later re-install the catalytic converter.




3.) Remove the converter's top heat shield. This is the heat shield that you see when you open the hood, which has a little image of a crossed-out hand on it. There are four bolts (I can't remember if they are 10-mm or 12-mm). The lowest bolt, near the radiator fans, takes a hand wrench and some patience (or a ratcheting closed-end wrench would come correct). When replacing these bolts later, you will want to put some anti-seize on the threads. You do not need to remove the A/F sensor -- just unplug it so the wire can pass through the hole.




4.) Once the heat shield is removed, you will see five 12-mm bolts fastening the converter to the manifold. Leave these bolts in place for the time, but spray them with PB Blaster or another penetrating oil. Move next under the car to first remove the bolts on the exhaust pipe end of the converter.




5.) Under the car, remove the spring bolts which connect the bottom of the converter to the exhaust pipe. The spring will be completely relieved of tension by the time you can pull the bolt free, so you do not need to fear that it will spring out uncontrollably.


Note: the picture below shows the "good" Rav4, which was entirely missing the exhaust brackets, or "manifold stays", in Toyota-speak. There was a recall in the US for these cats sometime in the mid-2000's, and apparently the dealer who did my sister's car didn't even bother to put the brackets back on. If you find this case on your Rav4, it is highly advised to install the brackets, and also extremely likely that you will not be able to re-use your exhaust pipe gasket, because it will likely be severely worn. The part numbers for the brackets are 17118-28020 (passenger side) and 17139-28010 (driver's side) , and they cost about $26 together from localpartsshop.com.​





6.) Remove the two bolts which fasten the manifold stay (the bracket) to the engine, one on each side. The bolt on the passenger side is easy to access: just remove the bolt the connects the bracket to the catalytic converter. The bolt on the driver's side is a little more difficult: you can try to remove the bolt that connects the bracket to the cat on this side, but you might find it easier to remove the bolt that connects the bracket to the engine instead. Read the instruction below and look at the pictures to see what I mean.

The key for the driver's side (LHS) is to take the TOP bolt, which connects the bracket to the engine, instead of the bottom bolt, which connects the bracket to the converter. While it will appear that you need to remove the radiator to get to this bolt, you DO NOT -- just follow these instructions:


Look at the picture below, which was taken while standing in front of the Rav, looking down (see the top sensor and the radiator fan housing); there is a ratchet wrench with a 3" extension in place, ready to remove the bolt. You can't see the bolt for the bracket, but you CAN get a tool on it. To do this, I went under the car and reached around with the socket and extension in my hand, until I found it. Then, either from above or below, you can attach the wrench and remove the bolt. Once you do it, you'll see that its actually not that bad (though it took me a while to figure this out!).​








7.) Once the two bracket bolts are removed, head back up to the top of the converter and remove the five 12-mm nuts which fasten the converter to the manifold studs:


- A deeper-than normal socket is required for these, so spend the $2 at Home Depot and get a 12-mm deep socket.
- Remove the front part of the air intake for better access to the top bolts.
- The bolt closest to the passenger side is in a position such that I couldn't get either a u-jointed socket on it or a deep socket, so for that one I just used a standard 12-point closed-end wrench. I tapped the end of the wrench with a hammer to break it free, then just used patience to remove it with the closed-end wrench. You only need to turn these a few times with the wrench, anyway, and they they should be finger-loose.​







8.) Now you can remove the converter by simply pulling it off the manifold studs, then up and out, being sure to watch the clearance on the oxygen sensors as you pull it out.


9.) You can now see the full manifold gasket, which will be sitting on the manifold studs. The exhaust gasket will likely be snugly fit onto the bottom of the converter. Remove both of the gaskets and inspect them carefully if you plan to try to re-use them. I lost my pictures of this, but you don't really need pictures -- its pretty straightforward!


10.) Now you can remove the sensors (actually, you can remove the sensors while the converter is bolted on, too, if you are just replacing the sensors. However, it is pretty tight to remove the lower driver's side sensor (Bank 2 Oxygen Sensor), so you might have to remove the converter to replace that one). Place the converter manifold-side down on a cardboard surface. Use the 22-mm Oxygen Sensor Socket and a breaker bar to break the sensors free, then once they are free, unscrew them by hand to prevent damaging the electrical wires. Carefully inspect the wires for damage, and repair them/insulate them if your see any cooper wire showing through.


11.) Remove the front and rear heat shields from the old converter and install them on the new converter.


12.) Install the sensors on the new converter, applying just a little bit of anti-seize to the treads. Torque each to 33 ft-lbs.


13.) Clean the manifold surface to remove the carbon build-up. Check out this great video: he cleans the manifold surface at about 3:50 (
)


14.) Install the manifold gasket by placing it back on the studs on the manifold. Install the exhaust pipe gasket by pressing it into place on the bottom of the catalytic converter.


15.) Place the converter back onto the exhaust pipe, being careful not to hit the sensors on the radiator fans. Install the five 12-mm nuts to finger-tight on the manifold side, then check the alignment of the bottom of the catalytic converter with the exhaust pipe under the car. Align the brackets.


16.) Bolt the brackets back in place (torque to 33 ft-lbs), then fasten the spring bolts a bit, but not completely. Check the alignment on the manifold, and tighten those nuts a bit in a random pattern. Torque the spring bolts to 32 ft-lbs, and finish tightening the manifold nut to a final torque of 27 ft-lbs. Here are other torque values (note the key on the bottom right):




17.) Install the main heat shield, being sure to pass the A/F sensor wiring connector through the hole.

18.) Re-connect the sensor electrical connections. Use zip-ties to tie the wires if your plastic clips broke. Be sure that the wires will not be damaged by any nearby moving parts, especially the belt and fans.

19.) Re-connect the battery, clear the engine bay of tools and anything else, and start the engine. The engine may cycle into a low idle, or even very low idle, and it might be shaky or even feel like it is going to stall. This is caused by the ECU resetting. Let it idle about about 5 minutes, then take the Rav for a minimum 10 - 15 minute drive at normal speeds, including freeway speeds, to allow the ECU to re-learn.

The Check Engine light will be off, from having been re-set by the lack of battery power. My sister's Rav4 needed about 55 miles and four start/stop engine cycles in order for the ECU to display "Catalyst Complete," and "Oxygen Sensor", etc on the "Emissions Readiness" display on my OBD reader. Once it showed "complete", we took it in right away for the smog inspection. It passed, just fine! No codes have returned, and it has been one month and about 500 miles.

Hopefully this will work for you, too! Please post any tips that you discover in the course of doing this job, or more pictures of important items. Good luck!
 

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Have you any experince reagrding O2 failure? I had an inspection at Toyota Service and they told me i have a faulty on my O2 sensor on the converter.
When i changed the converter take a look on O2 sensor. (Attached some pic form)

As you see there is an silver contamination and a strange little spot on. (@Toyota they offer me a sensor change, but i would like to investigate the root cause)

Do you have any idea which caused this? (Or this is normal failure?)

Thank you.
 

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Discussion Starter #5
Have you any experince reagrding O2 failure? I had an inspection at Toyota Service and they told me i have a faulty on my O2 sensor on the converter.
When i changed the converter take a look on O2 sensor. (Attached some pic form)

As you see there is an silver contamination and a strange little spot on. (@Toyota they offer me a sensor change, but i would like to investigate the root cause)

Do you have any idea which caused this? (Or this is normal failure?)

Thank you.
denver3, I'm not sure, but that rather looks like someone might have gotten anti-seize on the sensor tip. But it could be something else -- I really don't know! The one picture looks a bit like a finger print.
 

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Nice detail in the write up. I had 2 P0420 codes and another code that I can't remember come up on a code reader. The code i can't remember was for a misfire in the engine. My husband tested and found the misfire in cylinder 4 and hoped that the misfire was causing the P0420 code. He changed a coil pack over the spark plug and reset all codes and got the misfire fixed but had the P0420 codes come back. He doesn't know if he needs to replace catalytic converter or check the O2 sensors first.

Recommendations???
 

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I used this hack to get rid of the P0420 code on a friends 200,000 mile 2003 Civic.
It was a last ditch effort because the owner had just spent $1000 at Sears to have the converter replaced six months earlier.
 

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Not looking for cheap and easy hack. I need/want it fixed since my husband and I are about to have a kid. I don't want to drive something knowing there's still an issue.
 

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Not looking for cheap and easy hack. I need/want it fixed since my husband and I are about to have a kid. I don't want to drive something knowing there's still an issue.
Okay call it a "fix" instead. As I said it was the only way I could get it thru emissions after replacing both the converter and sensors.
 

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help needed

Hi guys umm in need of some assistance here... my 2001 rav4 only has one sensor on the maniverter, and i suspect it is faulty, gonna get it tested tomorrow, so i wanted to know if Denso 234-4048 Oxygen Sensor would be the correct replacement for it, it comes up from the bottom of the maniverter and plugs in right by the alternator


thanks for any help you can give
 

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No need to label the electrical sensor connector locations. The upstream a/f sensor connectors are identical to each other, but due to wire length, the short wire a/f sensor installs on the passenger side while the longer wire a/f sensor installs on the driver's side.......as for the down stream o2 sensors: Their connectors are identical to each other yet different from those of the upper a/f sensors. And same thing goes regarding different wire length. There is no way possible to improperly install the sensors onto the Rav if one are in a wrong location.

Anyhow, this is an excellent write-up. I removed and replaced a Rav 4 catalytic converter recently. The converter was bad with a P0420 code. I would suggest, using a 22mm o2 sensor socket tool to remove the B2S1 sensor from the converter prior to removing the top heat shield. Removing the sensor before removing the heat shield will make it easy to remove the heat shield.

With the B2S1 sensor in place, the heat shield will have to be bent out of shape to remove it (the shield) from the vehicle.

Another proper tool which is useful when removing this catalytic converter is a 15° ratcheting 12mm wrench with reversing toggle switch.

I removed the converter from the Rav in 20 minutes.
 
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