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Old 01-24-2009, 11:36 AM   #21
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Leave o2 sensor in place. Snip signal out wire and replace signal with analog output from appropriately programmed LC1. Done.

I'm dong this, but a bit more complicated as I'll have the LC1 "move" switchpoint up one point from stoich to 15.7:1. Not a problem to fool the computer on both sensor since LC1 has 2 analog outputs.
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Old 01-24-2009, 07:21 PM   #22
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obd1 > *
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Old 01-24-2009, 07:38 PM   #23
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My 99 had 2 cats from the factory. I cut off the 2nd cat, and used a piece of pipe to replace it. The 2nd O2 sensor is after the 1st cat. When I went turbo, I replaced my stock manifold and DP with aftermarket ones, which now I am catless. This made my CEL come on. I bought a simulator. Then I went to the local u-pull-it and snipped the pigtail off an O2 sensor that fit my car. The I wired the simulator directly to the pigtail and plugged it in to the secondary O2 harness on my car. I hid it so Mr. Inspection can't see it. I don't have a CEL anymore.
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Old 01-25-2009, 11:23 PM   #24
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I was totally happy with my simulator. I used a resistor instead of the sensor to save a bit of weight, and then all the wiring was under the dash instead of running it out under the car. Can't say I minded it, though my standalone also doesn't turn on the CEL, and I have a used O2sim for sale. :-)
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Old 01-25-2009, 11:29 PM   #25
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Quote:
Originally Posted by AbeFM View Post
I was totally happy with my simulator. I used a resistor instead of the sensor to save a bit of weight, and then all the wiring was under the dash instead of running it out under the car. Can't say I minded it, though my standalone also doesn't turn on the CEL, and I have a used O2sim for sale. :-)
Damn, man. I just ordered one Friday.
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Old 06-24-2010, 01:09 AM   #26
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Quote:
Originally Posted by evank View Post
A simulator is illegal, so whatever I write in this post is purely hypothetical. This fix may or may not be working great in my car.

Car had a CEL for "emissions too close to threshold" or something like that after a few months with a high-flow metalcore cat.

Under the driver's seat, very close to the trans tunnel, is a plastic-wrapped series of four wires. This is where the wires exit the car and go underneath to the rear O2 sensor.

Cut open the plastic wrap. The four wires (on an '04 at least) are: 1., black with white stripe (power), 2., white (signal in), 3., red (mostly wrapped in a second layer of white insulation - signal out), 4., black with red stripe (sensor ground).

Cut the red and black/red wires. Install a 1 megaohm resistor (1/4-watt or 1/2 watt) in the red wire. Then install a 1 microfarad capacitor jumping the red and black/red wires, forward of the resistor. Cover the wires with electrical tape or (better yet) heat-shrink tubing. I used electrical tape but I'm told it could melt over time.

Done.

This sends an acceptable voltage to the ECU, so it thinks all is well. (These aren't the droids we're looking for .... move along .....)
Hi MT folks -- sorry to bring back an old thread. Recently a bunch of people contacted me asking for a diagram. So I am complying. Here's an ugly diagram, but it's accurate.

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Old 06-24-2010, 10:48 AM   #27
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What about pulling out the CEL bulb?
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Old 06-29-2010, 02:57 PM   #28
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Quote:
Cut the red and black/red wires. Install a 1 megaohm resistor (1/4-watt or 1/2 watt) in the red wire. Then install a 1 microfarad capacitor jumping the red and black/red wires, forward of the resistor. Cover the wires with electrical tape or (better yet) heat-shrink tubing. I used electrical tape but I'm told it could melt over time.
when you say forward of the resistor. is forward towards the o2 or towards the ecu.


also i have a 63v microfarad capacitor laying around, will that do the job? it's also polarized so witch wire would go into the + side?




edit: didn't see page 2 with a sweet ms paint how to.

Last edited by jeff_man; 06-29-2010 at 04:03 PM.
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Old 06-29-2010, 07:30 PM   #29
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Quote:
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also i have a 63v microfarad capacitor laying around, will that do the job? it's also polarized so witch wire would go into the + side?
I don't know.
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Old 12-24-2011, 12:24 AM   #30
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I am going to do this CEL mod on my 04 MSM (no cat) but had a question about whether I should use a polarized or non-polarized capacitor. Also, the capacitors range from 50v to 350v so I wasn't sure which one to use. I am hoping that based on the picture below, someone can tell me which one they successfully used to complete this mod. Thanks for your help!
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NB Cat Delete CEL fix question-capacitor.jpg  
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Old 12-24-2011, 01:45 PM   #31
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Quote:
Originally Posted by austexmiata View Post
had a question about whether I should use a polarized or non-polarized capacitor.
Shouldn't really matter. Most electrolytics are polarized, the non-polarized caps are typically used in applications where they're exposed to AC waveforms, such as in speaker crossovers. In this application, a polarized cap is fine as one leg is going to ground.

Quote:
Also, the capacitors range from 50v to 350v so I wasn't sure which one to use.
That rating indicates the maximum voltage that the cap can be exposed to without failing. Since the maximum voltage generated by an O2 sensor is a little under 1 volt, any cap you can find will work just fine.
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Old 12-24-2011, 06:49 PM   #32
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I appreciate your response. I'm going to go ahead and use the polarized 160v capacitor.
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Old 12-26-2011, 07:36 PM   #33
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What voltage does the ECU want to see from the post-cat O2 sensor signal line to make it happy? (The cat I have is somewhat "less than optimal" from the ECU's point of view as compared to the original OEM cat + the post-cat O2 sensor has been abused to death...or maybe the wrong one, I don't know but I'm tired of f'cking around with it - it is inspection time again dammit).

Last edited by secretsquirrel; 12-26-2011 at 07:51 PM.
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Old 04-07-2012, 12:21 AM   #34
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sorry for bringing up a dead thread...but after reading this, i had a question.

after putting that cap between the red/black and red wire, do you just leave the part of the red/black wire that goes to the sensor itself unhooked? or do you re-solder it to the node/joint where the cap is already soldered to the red/black wire?
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Old 04-09-2012, 03:23 AM   #35
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There are mini-cats now that go between the bung and the O2 sensor. Much easier than fooling the ECU or jacking with the wires ... the O2 sensor sees exhaust air that is post-cat, like it's supposed to. The main cat can then be deleted if so desired.


Edit: Mini cat from Big Daddies Garage.

Dynotronics makes one as well; appears to be of higher quality but significantly more expensive.
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