I had a P0036 appear about 2 months ago: says its Bank 1, Sensor 2 O2 sensor. I checked the harness, everything looked good, so I turned off the code. It came back a few days later and then switched itself off for a while. When it reappeared last week, I tried swapping the sensors but eventually it came back again.

I ended up buying new NTK sensors for both downstreams. Cleared the code, and it came back this morning. I checked the O2 Sensor fuse and its fine. Any other ideas for what this could be? Driveability seems fine, no differences, but its an annoying CEL.

In separate news, I've got rattling INSIDE both cats. One isn't so bad (driver side), but the passenger side one is worse. At low speed/ start of slow accelerations, I get the rattle/ ting as if it was a heat shield metal on metal. I had my heart shields both tack'ed on, so its not them. I don't suppose there's much that can be done since it's INSIDE the cats...aside from replacing (gulp $). Any suggestions here also would be appreciated.

Thanks!

 

I'm going to say that the cat's are pooched.

 

Before I wholeheartedly agree with Happy Hummer, I would like to know how many miles on the those cats. That may be in addition to a problem in the O2 Sensor heater circuit.

Have you looked at the fuse box for the O2 Sensor (#47) ?

 

Yes, I checked #47 and its ok. The vehicle has 186,500km on it.

I called my custom exhaust shop in Toronto and he said the cats are almost impossible to find/ very expensive even to get in. He says he can custom do 2 high flow cats, installed for around $700 CAD. Which seems pretty reasonable.

The P0036 code went off by itself yesterday. I;m going to run a bottle or two of the Dura Lube Severe Cat Cleaner through it, and hopefully that prolongs things a bit.

I figure it should be safe to drive on a bit---I haven't noticed any power loss or gas waste, and there are no exhaust smells inside the car or bay or anything.

 

I don't know about finding them in Canada, but you can buy them here, several places have them in stock. The left sides are high $200s just under 3, the rights are about $330.
For sake of simplicity, say the parts run $600, you guy's price is pretty reasonable indeed.

However, keep in mind that the stock setup has 2 cats on each side, small pup cats up front monitored by the downstream O2 sensor, and 2 larger cats after the fronts that are not monitored.

If I were faced with your problem, I would go have the work done by your exhaust guy using high flow cats and loose the back two as well.

Please let us know how that goes when you get that done and drive it a bit.

 

Will do, I plan on getting it done in the next couple weeks.

Thanks as always for your sound advice!

 

So I took it to my mechanic today who ran electrical tests. Now, in addition to the P0036 I had a P0141 come up and also a P0054...all related to that same downstream bank 1, sensor 2 heater.

They said everything seems to be in spec, all the voltage and grounds and fuses and everything seem fine. They think it could be an ECM issue, otherwise they don't really know.

I remember last year I had a P013B code (HOS2 slow response lean to rich sensor 2). After checking that O2 sensor was connected and there were no issues, I found a TSB online saying that the ECM needed to be flashed with the newest service pack from the dealer. So I took it there and the dealer reprogrammed the ECM with latest update as per service manager and TSB. They performed Crankshaft variation re-learn, and this fixed that issue I've never had any further issues with that code. I'm wondering if it might be something similar for this one as well?

Any thoughts? I haven't really noticed any gas loss or power loss, but I just hate seeing this CEL come on, and go off, then come on.

 

Took it into GM today and their electrical expert tested everything (shelled out for electrical testing now a 2nd time). All he can suggest is "using AC delco sensors"---but I already swapped my original AC delco's and still had the P0036 code, then bought Bosch and still had it, returned those and now have NTK sensors on there and still am getting the P0036 code. I do not think it is sensors.

They have no clue. They say all wiring, harness, ECM, fuses, everything electrical checks out.

Any possible other ideas?

 

Try using very little of this on your connections. It's stupid expensive but seems to help with some electrical gremlins.