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Old 07-11-2009, 01:36 AM   #1
wrecklessfool
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O2 sensor bypass and relocation DIY with pics

So I found the thread that autobot325i had written up on installing the O2 simulator from O2sim.com. His thread can be found here: http://forum.e46fanatics.com/showthr...325i+simulator

Not to knock his write-up, but I found it difficult to follow the steps he had posted as to which wires went where, etc. After doing a good amount of research on this forum, as well as a few others, I decided to tackle the job. In my case, I relocated the post-cat O2 sensors due to fitment issues involving the tight clearances with my ebay headers. You may decide to relocate the sensors in favor of installing wide-band sensors or whatever the reason may be. As you may or may not know, the simulator alone will not rid you of the eye sore that is the Service Engine Soon light. If you remove the post-cat O2 sensors, your car should throw five (5) different codes. P2098, P2096, P2272, P0056, and P0036. The last two codes are for the post-cat O2 sensor heater failure. In order to perform a successful O2 sim install, you will either need to leave your sensors in the bungs on the headers with the heater wires connected and splice the simulator in, relocate the sensors but keep the heater wires on the sensors, or use an inline resistor to mimick the load that the heater element creates to fool the car into thinking it's all functioning properly. The only problem with going with resistors is that they are likely to fail after a relatively short period of time due to the immense heat created by the constant load placed on them. This has been proven in another member's application on this board, as well as a few others on different forums. Your best bet is to utilize the stock O2 sensor heater for long-term reliability.

My method of relocation is very cheap and provides a nice finished product. For the sensor relocation this is what is needed:

1-small galvanized electrical box with cover
2-18 MM 1.25 thread pitch nuts
1-small bolt 1 1/2 inches long with a matching nut
1-can high temp spray paint
4 feet of 14 gauge stranded wire

For the simulator, you will need to purchase:
1-O2 simulator itself from O2sim.com
1-small project box from radioshack
1-piece of double sided tape for outdoor use

I decided I did not want to cut in to the main harness of the car, so I cut the wires on the O2 sensor harness itself. If I want to revert back to stock, it's a simple plug-and-play operation

Now for the DIY with pics These directions are intended for those desiring to do a sensor relocation similar to mine.

First take a look at your simulator and ensure you ordered and received the correct unit. You should have one black wire, one red wire, and two white wires. Next, cut your O2 sensors off the end of their harness. Make sure you leave about 2 inches on the white wires. You can clip the black and gray wires at the sensor itself to retain as much length as possible on the harness side. You will need the two white wires on each sensor later to supply the voltage needed for the heater to function properly, so make sure you leave enough wire to allow a connection. Once you have done this, take the gray wires from both sensors and connect them together to the black wire on the simulator. Then, connect the black wire from each sensor to the two white wires on the simulator. It does not matter which white wire from the simulator goes to which sensor as they both perform the same function. Leave the red wire from the simulator disconnected at this time as you will use it to tap in to a 12V power source in the engine bay. DO NOT TAP IN TO THE HEATER WIRES ON THE SENSORS FOR 12V AS PER THE INTRUCTIONS INCLUDED WITH THE SIMULATOR!!!!

When you're done with this part, your connections should look like this:

Photobucket

Photobucket

This next picture is just to give a reference to the white wires which are used to power the heater circuit. The connectors pictured are not recommended for the final install. I just had them on there for test fitting.

Photobucket

The O2 sensor harnesses are ready to be re-installed on the main engine wiring harness (without the sensor connected), and routed to the "drug bin." Take the O2 sensors you have cut from the harness and install them into the galvanized electrical box as shown in the pictures below. I punched out all of the removable plugs to aid in ventilation of the heat created by the sensors. Install the 18 MM 1.25 thread pitch nut on to the sensor from the inside of the electrical box. Once evrything is tightened down securely, clean the outside of the box with brake cleaner or something along those lines. Tape off the remaining portion of the white heater wires still attached to the sensor, and shoot the entire thing with the high temp paint. After it dries, it's ready to mount. I used the threaded tab on the inside of the "drug bin" compartment, but I used a bolt small enough to slide easily through both the electrical box and the threaded tab. Install a nut on the bolt on the underside of the threaded tab and tighten securely. Here is what mine looked like when complete without the cover on:

Photobucket

Photobucket

Next, you'll want to tap in to a 12V power source which is only providing voltage when the ignition is on. Use a multimeter to find the red/white wire in the loom which runs in front of the interior cabin microfilter. I removed a plastic fastener on the outside of the drug bin to run the red wire from the simulator to the 12V power source. You will want to SPLICE into this wire for your power source. I decided to install a peice of heat shrink along the length of the red wire to give it a bit more insulation and to help protect from abrasion should it move around a bit. Then, take your small project box and use a dremel to create a hole on one side of the box to allow for the four wires to go through without being pinched. Make the hole just large enough to allow the wires to pass through. If you're so inclined, you may place a dab of RTV sealant on the hole to keep moisture out of the box. This is what mine looked like when I finished this step:

Photobucket

Photobucket

Here is where I ran the 12V power wire in to the drug bin:

Photobucket

Next, use the 14 gauge wire to extend the white heater wires from the O2 sensor harness to reach the relocated O2 sensors mounted in the electrical box. You need to do this because the sensor harness is about 8 inches short of being long enough to reach the relocated sensors. It doesn't matter which white wire goes to which white wire, as long as the two white wires from each harness go to the same sensor. Polarity is not important as the heater element is basically a resistor. I opted for black 14 gauge wire, so don't let the color throw you off. The white wires from the harness are connected to the 2 inches of white wires you left on the sensor in the first step. Here is what it should look like:

Photobucket


The main work is done at this point. Now just clean up the mess of wires you have going on and make them as presentable as you desire. I used a lot of small zip ties and mounted my small project box up with a peice of double-sided tape. Here is my finished product:

Photobucket

Photobucket

Photobucket


My setup has worked flawlessly! If anyone sees anything I may have neglected to mention, please post up. I hope this helps someone, as it took me forever to write! Best of luck. If you have questions about the install, just post 'em up
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Old 07-12-2009, 02:03 AM   #2
Drifto
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Very creative way to solve the problem!
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Old 07-12-2009, 02:24 AM   #3
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Nice DIY, well done!
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Old 07-12-2009, 03:27 AM   #4
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I was so frustrated with the other writeups, this is awesome.
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Old 07-12-2009, 12:27 PM   #5
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Thanks for the props guys. It took a lot of trial and error to end up with the final product. Trying different setups and having them not work out kept getting me frustrated...finally I got something here that is solid and dependable!
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Old 07-15-2009, 07:33 PM   #6
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Ok, I've been debating on getting headers for my car for this very reason. The O2 sensors. I've read on here SOOO many times about the SES light coming on, and all that stuff. And not being able to pass VET's. Well, the VET's doesn't really matter to me, I live in Kentucky. No VET in Kentucky. Anyways, I decided if I do get headers, I'm gonna go with the E-Bay specials. I've been looking at the headers on there, and they all come with O2 sensor holes and stuff. Four O2 sensor holes to be exact. However, even with the O2 sensors installed into these locations, will the SES light still come on? Or am I missing something here? Are there more O2 sensors? I'm sorry, I didn't mean to invade your thread, I just wanted to clear up some information before I spend the money on headers and end up regreting it.
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Old 07-15-2009, 08:47 PM   #7
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Your post cat, or rear O2 sensors will throw an SES code if installed in the aftermarket headers. You can just plug the rear O2 sensor holes with a large 18 MM 1.25 thread pitch bolt on the headers and relocate the sensors and add the O2 simulator. I have had my car like this for some time now and have no SES light. Good luck!
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Old 08-07-2009, 07:42 AM   #8
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UPDATE: I have driven over 1200 miles with this and have no SES light!!
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Old 09-20-2009, 02:28 PM   #9
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I just did this and it is AWESOME!! I haven't driven too far but so far no SES!! The DIY was really easy to follow. Thanks for the write up. I would not have been able to do this without the DIY. I still need to paint the galvanized box but it has been raining here for 7 days so I have to wait til it dries up.


Tapping into the wire loom to power the O2 sim. Routed it through the grommet.


This is where I routed the O2 sensor wire harness to the drug bin and the power wire for the O2 sim.


The project box that contains the O2 sim.


The box that contains the O2 sensors.


The entire section.
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2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
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Last edited by Minnoe07; 09-20-2009 at 05:51 PM.
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Old 11-24-2009, 10:13 PM   #10
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Just an update on the O2 sims.

I just passed emissions here in GA with flying colors!

There is one catch with these sims though. On long road trips, 4+ hours long, the O2 sims will trip a CEL. They are for lean condition in banks 1 and 2. I also had a pending code for a rich condition in bank 1. I don't know exactly why this happens, but it only happens on long road trips. These codes are different from the codes that you get with the non-foulers. You usually get the inefficient catalyst code with the non-foulers. (PO030 IIRC).

I reset the CEL since then and there hasn't been any light since. And just to clarify, I went for emissions after the long road trip and it was fine.

Definitely worth the money.
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Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
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Old 11-24-2009, 11:03 PM   #11
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Maybe I missed the point of this? Is this only needed if you have after market headers on? Does the SES light only come on if you go with Ebay special headers or any brand with bring this up? As for the write up very well done, use of pictures is always a great way to show it.
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Old 11-25-2009, 04:48 PM   #12
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Yes, you can use resistors for the heater circuits to remove the O2 sensors completely, but it has been known to fail because the heat generated causes failure. Using the O2 sensors as the heating elements, which are designed to take the heat, creates a more reliable end product.

This is done so that your car will not throw a catalyst inefficiency code after having deleted the catalytic converters that are located in the exhaust manifold.
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2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
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Old 11-25-2009, 07:57 PM   #13
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Quote:
Originally Posted by Minnoe07 View Post
Yes, you can use resistors for the heater circuits to remove the O2 sensors completely, but it has been known to fail because the heat generated causes failure. Using the O2 sensors as the heating elements, which are designed to take the heat, creates a more reliable end product.

This is done so that your car will not throw a catalyst inefficiency code after having deleted the catalytic converters that are located in the exhaust manifold.
Don't the Cats come after the exhaust manifold or does BMW have something inside the header? Or is this assuming you cut out the cats when installing an after market exhaust system?
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Old 11-25-2009, 10:12 PM   #14
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Cats are an integral part of the exhaust manifold.
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2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
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Old 11-25-2009, 10:37 PM   #15
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With this setup would a car pass CA smog?
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Old 01-14-2010, 09:11 PM   #16
Minnoe07
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If your inspector is blind...... maybe......
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2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
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Old 01-14-2010, 09:23 PM   #17
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UPDATE 2: Yes, on long road trips your car will throw an SES light. If you don't have a reset tool or don't care, driving around town for about 40 miles after you park for any length of time after your road trip will shut the light off. No need to reset unless you're going for inspection right away or it just plain bugs the crap out of you. I alo noticed that on a 11 hour road trip with one stop for gas, my SES light was not triggered. I made this trip twice and had no light. I believe that the cold weather kept the light from popping on. I only experienced the SES light in warmer and hotter weather...never in the cold. Again, no worries if it does pop on...just drive it around and you're all set.
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Old 01-15-2010, 10:37 PM   #18
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Great write-up; always nice to see someone contributing to the community. Admins, lets get this moved to the DIY section so that others can find it more easily!
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Old 02-13-2010, 08:44 PM   #19
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where did you get the 18mmx1.25 nuts? I cant find it anywhere!
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Old 02-13-2010, 08:51 PM   #20
Minnoe07
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ebay or your closest muffler shop. Search for O2 sensor bungs.
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2004 330Ci 6 Speed; UUC Sway Bars; Powerflex RTAB's and FCAB's; KW V2 Coilovers; 3.38 OS Giken LSD
Z4 Finned Diff Cover; Headers; M-Tech II Rear Bumper and CF Diffusor; CF Trunk; CSL Front Bumper
M3 CF Hood; DICE I-Pod Kit; JTD Rear Shock Mounts; UUC Front Strut Bar; O2 Simulators
ESS TS2 Twin Screw Supercharger

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