No cat and no engine light
- Thread starter ram_man
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Originally Posted by Gasbuggy
I remember doing a catless mid on my 99 Cobra and it took a few hundred miles to throw a code, numerous forum members had similar experiences. Some cars don't notice it easily.
Right. I helped a neighbor remove the cat on his Mitsubishi (I think it was like a Galant or a Diamante) because it had gotten plugged/fouled and was causing stalling/idle issues and it didn't register a p0420/CEL. I included a screenshot from a "tuners" forum where one member says he's got a cat bypass pipe on and never gets a CEL. Even with a CEL p0420 code the car will still run, albeit not the most efficient, because the ECU will stay in "open" loop.
I got my interest peaked and checked out YouTube and there are DIY videos on YouTube to show you how to "fool" the ECU into thinking the cat is still there. One method is to move the downstream sensors out of the exhaust flow with a spacer and the other is to alter/fix the O2 output voltage by wiring in cap/resistor combo. I'm not saying this is what the seller of the Saturn is doing but it could explain why there's no CEL after he removed the Cat. (that somehow the bypass pipe the seller installed is tricking the ECU into thinking the Cat is still there).
Just speculating here but I don't think his ECU is looking for the Cat either. My 2009 Kia ECU program actually looks for the Cat and it's operating temp as part of the emissions system check. My Torque App will display the status as either a green, red or "not ready" status.
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2019/06/full-85545-33315-screenshot_2019_06_08_03_27_47_1.png "[Linked Image]")
I remember doing a catless mid on my 99 Cobra and it took a few hundred miles to throw a code, numerous forum members had similar experiences. Some cars don't notice it easily.
Right. I helped a neighbor remove the cat on his Mitsubishi (I think it was like a Galant or a Diamante) because it had gotten plugged/fouled and was causing stalling/idle issues and it didn't register a p0420/CEL. I included a screenshot from a "tuners" forum where one member says he's got a cat bypass pipe on and never gets a CEL. Even with a CEL p0420 code the car will still run, albeit not the most efficient, because the ECU will stay in "open" loop.
I got my interest peaked and checked out YouTube and there are DIY videos on YouTube to show you how to "fool" the ECU into thinking the cat is still there. One method is to move the downstream sensors out of the exhaust flow with a spacer and the other is to alter/fix the O2 output voltage by wiring in cap/resistor combo. I'm not saying this is what the seller of the Saturn is doing but it could explain why there's no CEL after he removed the Cat. (that somehow the bypass pipe the seller installed is tricking the ECU into thinking the Cat is still there).
Just speculating here but I don't think his ECU is looking for the Cat either. My 2009 Kia ECU program actually looks for the Cat and it's operating temp as part of the emissions system check. My Torque App will display the status as either a green, red or "not ready" status.
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Originally Posted by ram_man
It recently passed inspections with all the monitors ran and ready. He showed me a video that the engine light works but isn't currently on. How can this be ?
All the monitors don't have to be completed on 2002 models to pass inspection. One can be incomplete and I'm guessing it was that one. I just passed a 2008 Pontiac with one incomplete. But that begs the question why are you making such a big deal out of this one issue on a $1,000-$1,500 car. I'd be way more concerned about the transmission condition or how cold the A/C blows.
It recently passed inspections with all the monitors ran and ready. He showed me a video that the engine light works but isn't currently on. How can this be ?
All the monitors don't have to be completed on 2002 models to pass inspection. One can be incomplete and I'm guessing it was that one. I just passed a 2008 Pontiac with one incomplete. But that begs the question why are you making such a big deal out of this one issue on a $1,000-$1,500 car. I'd be way more concerned about the transmission condition or how cold the A/C blows.
He added a spacer to keep the rear o2 out of the exhaust streaem. Some guys will cut the old sensor bung off and weld it on top of the new one to space it.
Up here if the cat isn't present on a visual - it doesn't pass.
You can get a boneyard cat from a modern engine of similar dispacement and weld it in. Make sure the harness is there for the post cat monitor.
You can get a boneyard cat from a modern engine of similar dispacement and weld it in. Make sure the harness is there for the post cat monitor.
Originally Posted by ARCOgraphite
You can get a boneyard cat from a modern engine of similar dispacement and weld it in.
No you can't. Junkyards can't sell cats legally.
You can get a boneyard cat from a modern engine of similar dispacement and weld it in.
No you can't. Junkyards can't sell cats legally.
Since when is most business at a rural boneyard "legal"
Actually I was not aware of that.
Ok OP could buy a replacement or universal aftermarket cat and install it.
I will assume most all vehicles post 1996 are OBDII compliant and also use post catalyst monitoring.
Actually I was not aware of that.
Ok OP could buy a replacement or universal aftermarket cat and install it.
I will assume most all vehicles post 1996 are OBDII compliant and also use post catalyst monitoring.
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It's my belief that it's possible for O2 sensors to wear out/fail in such a way as to fool the ECU, especially if the ECU isn't well-programmed to test and detect this. No guarantee it will stay this way.
Graphing mode on the sensors in Torque Pro would tell the story.
Graphing mode on the sensors in Torque Pro would tell the story.
Originally Posted by ram_man
Well the car has the pre cat in the manifold. It doesn't have any trickery that I can spot the o2 are working correctly. So I bought it . It needs a few minor things but runs good and for the price I couldn't beat it.
Kewl..even if a DTC popped up due to an out of limits O2 voltage, the car will still run in open loop mode managing the fuel/air. It's what happens if you're cruising down the hwy and an O2 sensor goes bad on ya.
Well the car has the pre cat in the manifold. It doesn't have any trickery that I can spot the o2 are working correctly. So I bought it . It needs a few minor things but runs good and for the price I couldn't beat it.
Kewl..even if a DTC popped up due to an out of limits O2 voltage, the car will still run in open loop mode managing the fuel/air. It's what happens if you're cruising down the hwy and an O2 sensor goes bad on ya.
Does your state have emissions inspection?
Originally Posted by slacktide_bitog
Does your state have emissions inspection?
If he still has a good upstream Cat he should pass. Look at the emissions report and see how close to the tolerances the car is. In my State they don't go under the car so they have no idea if you've pulled the Cat. A DTC would be what triggers the technician of a problem in the emissions system.
Does your state have emissions inspection?
If he still has a good upstream Cat he should pass. Look at the emissions report and see how close to the tolerances the car is. In my State they don't go under the car so they have no idea if you've pulled the Cat. A DTC would be what triggers the technician of a problem in the emissions system.
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That's an anomaly for sure. There's no way that downstream O2 sensor is seeing less O2 in the exhaust stream than the upstream with no CC in place. No idea how this is working, but mazel tov to you Sir!
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Originally Posted by JTK
That's an anomaly for sure. There's no way that downstream O2 sensor is seeing less O2 in the exhaust stream than the upstream with no CC in place. No idea how this is working, but mazel tov to you Sir!
It doesn't make sense but it happens. Aside from wiring in line cap/resistors or flashing the ECU to raise the voltage limit, tuners are using bypass pipes and welding either new bungs or non-foulers in place. My guess is the exhaust vacuum is sucking in ambient O2??? Just enough to produce an output voltage within limits and avoid triggering a CEL?? Dunno...
Good question for one of those tuner forums/shops.
That's an anomaly for sure. There's no way that downstream O2 sensor is seeing less O2 in the exhaust stream than the upstream with no CC in place. No idea how this is working, but mazel tov to you Sir!
It doesn't make sense but it happens. Aside from wiring in line cap/resistors or flashing the ECU to raise the voltage limit, tuners are using bypass pipes and welding either new bungs or non-foulers in place. My guess is the exhaust vacuum is sucking in ambient O2??? Just enough to produce an output voltage within limits and avoid triggering a CEL?? Dunno...
Good question for one of those tuner forums/shops.
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