Hi Everyone.

I'm new to post but have been reading this site for awhile and have found some great info, thank you all. I've got another problem now and need some help.

The CEL came on and my scanner, a scan gauge II, showed p0030 (HO2S Heater Control Circuit, Bank 1 Sensor 1) . OK, I changed the front right/passenger O2 sensor with a Bosch replacement. After the 2nd start CEL came on again and I got a p0031 code (HO2S Heater Control Circuit Low, Bank 1 Sensor 1). I realized that I had reset the OBD with my scan gauge but had never disconnected the battery. I once again reset with my scan gauge, disconnected the battery for an hour, and looked for any obvious vacuum leaks. I did find 2 lines disconnected on the intake (front of the engine ~8 inches after the air cleaner). Feeling pretty confident, I put it all together and went for a drive. All was great until I stopped for some groceries. Upon restart I got the p0030 code and CEL again.

I'm wondering what to do next? My plan was to get some carb/intake cleaner in the morning (I'm out) and spray around the air connections while the engine is running and listen for any leaks. It looks good but I'll verify. Beyond that I'm stumped. I read some posts about having to change both O2 sensors but I wonder if I missed something? The p0030 code is the front (before Cat) right or passenger side sensor correct? Do I really need to change the left as well? I couldn't get the clip back on the wire connector, could that be why it came back on? It seemed like a good tight connection.

I really don't want to drop another $170 for a sensor.

It's a 2001 S80 T6 with 90,000 miles on it.

Thanks,

Steve

ps. For everyone wondering how to change the sensor, here's what I did:

I have a broken ankle and wanted to keep it simple as it's kind of hard to get around right now. I jacked up the front so I could get under it. I removed what looked a frame cross member just aft of the plastic cover (big black piece you have to remove to change the oil, etc.) right where the exhaust made a bend and went up to the exhaust manifold. Attached to that was a mount/brace for the exhaust. Once all that was out of the way I could get my hands up there and use an O2 offset sensor socket ($3 from harbor freight) to get it out. Followed the line and disconnected the plug. I took off the front left wheel to make it easier. Had to cut a few clips, but it was pretty easy.

 

Ughhh, no luck today at all. When the car is cold started all is well. When warmed up, I get either P0031 or P0030 about 10 seconds after start.

A tech suggested looking at the amperage draw which I'm going to try tomorrow. I'm trying to figure out if my scan gauge will show the draw, elsewise I'll have to get down under it again. Has anyone done this?

Any other ideas?

Thanks,

Steve

 

I would check the pins on the plugs for the O2 sensor. The heater circuit is kind of a weird one. Usually it is just a bad sensor. But I have had a few that I had to change the rear sensor as well to get the code to stay away. But check the terminals and make sure all is tight.

 

OK, thanks. So if I try another sensor, you think I'm better off getting a rear on the same side than another front? I was also thinking about switching the two front sensors and seeing if the same code pops up. I was going to try and test the original one I pulled out as well.

 

You can try swapping the front ones first and see what happens.