NA - OBD-II woes

MAKG1

MAKG1

Touchdown! Greaser!
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MAKG
Gah. I'd rather be flying.

The wife's car is a 2000 Saturn SL-2 with a stick, and it flipped a "service engine soon" light.

It's the dreaded P0420.

So I hooked up the scan tool and found the following:
  • Fuel trims are moderately negative -- LTFT is -6% off idle and -8% at idle, and pretty steady. STFT is all over the place, from as low as -14% to +10%.
  • Both oxygen sensors are switching (hence the code). The front sensor passes all the O2 tests.
  • Front sensor is NOT carbon fouled. It's off-white, but has very few deposits on it. Mileage on the sensor is unknown, and could be very high. It is not original.
  • Idle MAP is 5 PSI, decelerating MAP is as low as 2 PSI. A vacuum leak or blow-by seem unlikely with readings like that.
  • No spark plug inspection yet; they were replaced about a month ago along with both coils to deal with a P0340 code (common problem on Saturns). At the time, wires tested good.
  • No fuel pressure, vacuum (aside from reading the MAP on the scan tool), or leak down tests yet.
  • ONCE, when driving (I was right seat with the scan tool), both sensors read 0 V for a second or two. That should be impossible.
  • The cooling system is pressurized and exhaust shows no visual evidence of white or blue smoke.

It's starting to look like the earlier cam code might have killed the cat. Not an answer I really like, as this vehicle has a cat integral with the exhaust manifold, and is made out of unobtanium.

Any ideas for making real sure this is the problem (or finding the "real problem" if it's different)? Fixing this is gonna be unpleasant and expensive if it really is the cat. But the real worry is that cats don't generally wear out -- they get killed by something else. However, I'm seeing no evidence of carbon fouling anywhere (so far) that could plug it up.
 
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Not sure how much they are, but O2 simulators are available for guys that want to run no Cat and not set off codes. They plug into the O2 pigtail for the after-cat O2 sensor and fool the computer into seeing what it should be with a Cat installed. Might be worth the $$$ to rule the Cat out. You're right though, if it does have a bad Cat, you'd still want to find the cause.

I would also look into the viability of a generic aftermarket cat in lieu of the expensive factory setup. Good muffler shop should be able to fab it in.
 
My Acura would throw this occasionally. I think it threw this code 3-4 times last winter. I kept resetting it and it would go a few hundred miles and come back on.

Last time I saw the code was about 10,000 miles ago. For some reason, it 'healed' on its own. Think it was the switch to summer blend fuel.

Try resetting it, run some seafoam through the gas, switch fuel brands, different octane and see if it goes away. Might also be worth replacing your O2 sensors if they are not expensive, check rockauto.com.
 
Your rear 02 is switching more or less like the front one is a tell tale indicator that the cat is junk..

Sorry I know that is not what you want to hear. The legal way to fix it is to replace the cat... However O2 sims are out there and you can make one. I would never install one in my shop for a customer since the fine is huge but if you do it yourself nobody is going to know
 
MAKG1 said:
[*]ONCE, when driving (I was right seat with the scan tool), both sensors read 0 V for a second or two. That should be impossible.
Click to expand...

been many many many many many moon, however reading this startled a memory. Look at the wiring diagram to be sure as I'm sure my memory is really foggy on this but going off of pure memory the map sensor feeds voltage to the tps or vice versa or something like that so a fault in one will affect the other. been there done that got the t-shirt may or may not help with the 0420 but random sensor faults, battery faults and likewise can set off some codes that otherwise wouldnt set.

For what its worth, I'm a retired auto mechanic. ASE master and advanced certified driveability specialist blah blah blah......
 
this will spoof the rear O2 to make it think the cat is working.

http://www.frsport.com/Mechanical-O2-Oxygen-Sensor-CEL-Fix-Version-2_p_16165.html

It will still get warm enough in most cases to not throw the P0422 code.

If you want to repl but don't want to use the cat in the manifold you need these:

WALKER 53324 Walker Flex Front Pipe

WALKER 15842 Ultra Converter
Must Use Aftermarket Front Pipe 53324; Federal Emission Models.; (Not legal for sale or use in California; Not legal for sale or use in New York for vehicles with CA emissions); Additional Parts Needed: 31533

WALKER 31533 Info
Category: Pipe Flange Gasket / Seal

All avail from Rockauto.com. I used to have an SW and I converted it to the pipe and separate cat. It's not a real fun job, but it worked fine, and then you can repl the cat by itself. If the rest of the car is in good shape this is what I would do again.

<edit; I see you are in CA. Well, you can't have it shipped to your place there, you'll have to have it shipped out of state, and then somehow get it to you privately. It'll work fine, but if you have to go to a referee, it may not pass CA smog by the visual check. But then again, it might. Some of the referees are pretty dumb, however they may see that it's been recently replaced and dig in further. Otherwise, you can buy the orig from rockauto at a higher price. Now, I'd go with the spoof device and see what happens at smog check time.>
 
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Honestly, even an $800 cat, or another cheap car, is less expensive than a Federal tampering fine. Not interested.
 
MAKG1 said:
Honestly, even an $800 cat, or another cheap car, is less expensive than a Federal tampering fine. Not interested.
Click to expand...

Ask for an aftermakrket cat. Even in California, you should be back on road for quite a bit less than $800.

My example here was getting two of them on to a 2003 F150 for $550 installed at local independent exhaust shop.
 
In general, the catalyst monitor is the least reliable monitor there is. Did you clear the code and then drive the car and have it come back?
 
Have you looked for a used one.

His system looks like this

16487__ra_p.jpg


14466-1__ra_p.jpg



48 state aftermarket that whole system is about $500

You need to identify if its the pre-cat at the manifold or the cat itself that is causing the code.

Also, as I and others mentioned earlier, reset the code and drive the car. These codes tend to come and go on older vehicles.If its something you reset every few thousand miles, just drive it. Makes zero difference in the car's economy.
 
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Oh and as for those parts, I found nothing aftermarket that is legal in CA.

I just had a shop put a completely new 3" exhaust on my suburban (cat, muffler, 3" tubing) for $350 including all installation and fabrication. Using universal parts. Only thing I kept was the exhaust manifolds.
 
Technically, he can't go aftermarket unless it's cert by the CARB. And CARB cert is pretty tough and costly so most mfg don't bother. They just slap the 'not valid for cars in CA' on it and go. The only upside is if Saturn(which is out of biz) GM tells him it's NLA, he can then take that to a referee and say 'part is NLA, I did my best, you need to waive it'. I've done this with older cars in the past and once it's waived you are good to go.

Depends on the ref you get. Some are cool and will check to see it's NLA then waive it through. Others will make you hunt for a 'qualified replacement of similar type' which goes back to the non-CARB parts. Then you get approval from the ref to install and test, and then they will waive it with 'modified system' in the computer and once again you are good to go. Most refs I've had in the past don't bother with the modified method.

Where it gets really interesting is when you remove an entire engine and substitute it for another different type of engine. The refs have a field day with those.
 
dell30rb said:
Oh and as for those parts, I found nothing aftermarket that is legal in CA.

I just had a shop put a completely new 3" exhaust on my suburban (cat, muffler, 3" tubing) for $350 including all installation and fabrication. Using universal parts. Only thing I kept was the exhaust manifolds.
Click to expand...

On this vehicle, the cat is integral with the exhaust manifold. That's why it's so FN expensive. It also means you can't get junkyard manifolds.
 
Is there a cost cap of compliance anymore at CARB? Used to be $200, then it was $300, but not sure if it's still around.
 
You live in California, too bad for this problem. You say both sensors are switching, are they both switching at the same level? If so then the converter is probably toast. Tap on the outside (without denting it), if you hear rattling then that's another clue things aren't good. If the 2nd sensor is only switching with a small (0.1v delta), then it may be something else. I went nuts with a code like this, turned out to be a crack in the y pipe and a bad PCV valve. Different code, but not what everyone was telling me to look for.

If the converter is gone, Magnaflow makes CARB replacements where you can cut out the old one and weld in a new one. The problem is California wants paperwork and I believe only licensed shops to do the work. The converter is probably a hundred bucks for your car.

The other thing to consider is catalytic converters don't fail generally unless a malfunction or physical damage causes it. Physical damage should be easy to see. A malfunction is more difficult, you want to make sure that you fix the problem or your new converter will fail quickly. One sign of an engine malfunction would be a converter that has turned blue from overheating.

Good luck, I hope you can fix it easily.
 
MAKG1 said:
On this vehicle, the cat is integral with the exhaust manifold. That's why it's so FN expensive. It also means you can't get junkyard manifolds.
Click to expand...

Duoh, just read this, that sucks.
 
docmirror said:
Is there a cost cap of compliance anymore at CARB? Used to be $200, then it was $300, but not sure if it's still around.
Click to expand...

Actually, there appears to be something better now.

With a failed smog check, I can retire the vehicle with no means test and get $1000 from the state.

I may just do that. Not spending $800 on a repair plus that $1000 gets me another cheap car. Last one I bought was only $1300 and I drove it for over 100,000 miles. Plus about $100 to fix up the air conditioner.
 
Sounds like a plan. I will reserve my commentary on the sensibility of the state giving people money for a running car, which is actually a low smog producer, even without a cat. That process is left to smarter people than me in the state gov.
 
MAKG1 said:
Gah. I'd rather be flying.

The wife's car is a 2000 Saturn SL-2 with a stick, and it flipped a "service engine soon" light.

It's the dreaded P0420.

So I hooked up the scan tool and found the following:
  • Fuel trims are moderately negative -- LTFT is -6% off idle and -8% at idle, and pretty steady. STFT is all over the place, from as low as -14% to +10%.
  • Both oxygen sensors are switching (hence the code). The front sensor passes all the O2 tests.
  • Front sensor is NOT carbon fouled. It's off-white, but has very few deposits on it. Mileage on the sensor is unknown, and could be very high. It is not original.
  • Idle MAP is 5 PSI, decelerating MAP is as low as 2 PSI. A vacuum leak or blow-by seem unlikely with readings like that.
  • No spark plug inspection yet; they were replaced about a month ago along with both coils to deal with a P0340 code (common problem on Saturns). At the time, wires tested good.
  • No fuel pressure, vacuum (aside from reading the MAP on the scan tool), or leak down tests yet.
  • ONCE, when driving (I was right seat with the scan tool), both sensors read 0 V for a second or two. That should be impossible.
  • The cooling system is pressurized and exhaust shows no visual evidence of white or blue smoke.

It's starting to look like the earlier cam code might have killed the cat. Not an answer I really like, as this vehicle has a cat integral with the exhaust manifold, and is made out of unobtanium.

Any ideas for making real sure this is the problem (or finding the "real problem" if it's different)? Fixing this is gonna be unpleasant and expensive if it really is the cat. But the real worry is that cats don't generally wear out -- they get killed by something else. However, I'm seeing no evidence of carbon fouling anywhere (so far) that could plug it up.
Click to expand...

Cam code?

Do you mean a P0341 (camshaft position sensor)?

If so, how old are the spark plug wires? That's usually the cause of that error. Saturn S-Series cars didn't have camshaft position sensors. Bad wires tripped a P0341, for some reason that I've since forgotten.

As for the cat... If the cat is bad, try a can of CataClean. It's one of the few additives that actually seems to do anything. (Frankly, I think it's mainly lacquer thinner.) Don't park over leaves after you use it.

Rich
 
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