MAKG1
Touchdown! Greaser!
- Joined
- Jun 19, 2012
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- 13,411
- Location
- California central coast
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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:
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.
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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