[2000TAinNE]

I own a 2000 Trans-Am and have added a couple of things and now notice a problem.

I added a K&N Cold Air Intake and a Diablosport 'Predator' chip. The car runs great for anywhere from 1 to 3 hours then the "Sell Soon" light, (check engine), comes on. I had it checked out and found out the catalytic converter was bad. Pontiac replaced it and told me the O2 sensors were bad. I replaced all 4 of those myself and off I went. Next thing I know the check engine light is on again. I took it over to the parts store and had the kid run the computer to check the codes and it was the left and right rear O2 sensors that came up bad. I then replaced those and went on my way. Well, now the check engine light is on again and I stopped over to the parts store again and the same codes came up, left and right rear O2 sensors. I literally replaced those 3 hours ago and they are coding out again. (p0137 and p0157 are the codes)

Any ideas? Does my car have a breathing problem? I still have stock exhaust on there with the cold air intake and the chip. If anyone has any ideas please feel free to post them up.

Thanks!

[oldbogie]

Originally Posted by 2000TAinNE

I own a 2000 Trans-Am and have added a couple of things and now notice a problem.

I added a K&N Cold Air Intake and a Diablosport 'Predator' chip. The car runs great for anywhere from 1 to 3 hours then the "Sell Soon" light, (check engine), comes on. I had it checked out and found out the catalytic converter was bad. Pontiac replaced it and told me the O2 sensors were bad. I replaced all 4 of those myself and off I went. Next thing I know the check engine light is on again. I took it over to the parts store and had the kid run the computer to check the codes and it was the left and right rear O2 sensors that came up bad. I then replaced those and went on my way. Well, now the check engine light is on again and I stopped over to the parts store again and the same codes came up, left and right rear O2 sensors. I literally replaced those 3 hours ago and they are coding out again. (p0137 and p0157 are the codes)

Any ideas? Does my car have a breathing problem? I still have stock exhaust on there with the cold air intake and the chip. If anyone has any ideas please feel free to post them up.

Thanks!

You haven't done anything so radical that the O2 sensors should be going up in smoke, I'd suspect the chip is tossing a fake code due to some not quite right programming.

Bogie

[carsavvycook]

IIRC p0137, and p0157, are codes for the heater circuits in the left bank sensors.

They use battery voltage to heat them up, and the ECU grounds them to complete the cycle. There should be a fuse, in the underhood fuse box, for the heater circuits in the O'2's. Check all of the fuses. One may have blown.

[2000TAinNE]

Thanks and thanks....

And I probably should have mentioned this as well but it escaped me at the time. During this "check engine" light period there is also a very noticeable decrease in power. The car falls flat on it's face off the line and bogs out/sputters randomly during acceleration. There's no backfiring or anything like that just a feeling like it is getting choked or does not have proper air flow. I assume this has something to do with the O2 sensors not working properly?? Once I get to a desired speed it will run fine at that speed/rpm though.

Thanks again for the speedy replies. I am going to check that fuse box now.

PS- checked fuses...they are all good. I was hoping it would have been that easy....darn!

[cobalt327]

An O2 sensor showing low voltage can be triggered by a lean air/fuel mixture.

This could mean there's water in the fuel, an exhaust leak upstream of the O2 sensor, injector(s) that are failing, low fuel pressure from a clogged fuel filter, fuel pressure regulator bad or not adjusted right, an intake gasket or upper/lower plenum leak- any vacuum leak, really, and the obvious burned, shorted or cut wiring.

There should be clean connections all the way through the wiring harness, and there needs to be a path for air to reach the O2 sensor as well, where the wires enter- this can't be clogged up w/dielectric grease.

That both sides are indicating a problem, would seem to point to a vacuum leak that could reach both banks, for instance. Whatever the problem is- it's managing to communicate between the two sides of the engine- like if the plenum were leaking.

Usually an EGR problem will set its own code, but is something else to consider.

[2000TAinNE]

OK....so this could end up being a real pain in the butt is what you're saying.

I installed the O2 sensors myself and ran the wiring the exact same as they were from the factory so I am going to rule out bad/damaged wires. The car was running on fumes today, prior to working on it, and I just filled it up with premium so I'd say the water in the gas is a non-issue as well.

I am going to check the fuel filter since I have never changed that, (car has 70k miles...eek). Also going to fire it up and spray around to see if I find any vacuum leaks. I'll keep you posted.

Thanks!

[cobalt327]

Originally Posted by 2000TAinNE

Also going to fire it up and spray around to see if I find any vacuum leaks.

If you can get ahold of a good vacuum tester- one that has an "undamped" needle that will show the "jiggling" associated with bad valves, etc. (not that I think your valves are bad- at least I hope not)- and test the engine's vacuum to see if it's low.