2019 I3s - code P1179 and burning electrical smell after using Rex

[odbcman]

I have a 2019 I3s with the Rex. Mileage is about 36,000. At least once a year I get code P1179 (O2 Sensor Signal Circuit Slow Switching??) while driving or when I just turn the car on and not using the Rex.

Two years the code P1179 occurred while driving and the Rex not running. I was close to a BMW dealership, so I decided to see what they had to say. All they did was turn the car on and off about 6 times and the code went away for about another year. They couldn't explain why it occurred. Any idea what this could be?

Last March I brought the car was into the BMW dealership for an electrical burning smell that occurred every time the Rex was used. I also let them know I was getting code P1179 randomly when the Rex was not being used. The smell according to the dealer was a leaking head gasket on the Rex. They replaced the head gasket but could not find out what was causing the P1179 code in the 3 weeks they had the car. I still have the burned electrical smell each time the Rex is used and now once again about a year later the P1179 code is back. I cleared the code with my code reader several weeks ago and it has not returned. The car is due for service in March 2024 and I'm going to bring this random code up again. The burning smell they tell me is just the heat off the Rex and nothing to be worried about.

Any ideas on code P1179 and is the burning smell normal when running the Rex? As a side note, the Rex is used very, very rarely on my part. If it's used by me, it may only be for a couple of minutes or during the normal 10-minute maintenance cycle.

 

[weajd]

Asking an obvious question -
Any oil leaks under the car or around on the engine?

 

[odbcman]

The car has no oil leaks anywhere. That was my concern, but I have been under the car and don't see any signs of any leaks.

 

[weajd]

The car has no oil leaks anywhere. That was my concern, but I have been under the car and don't see any signs of any leaks.

Assuming there is still oil remnants on the engine -
To reduce the smell - check the gasket around the hatch in the "trunk" for damage.
Research how to clean off grease/oil from the engine/exhaust carefully around electrical circuits.
High pressure washing may not be the best bet around the adjacent electrical motor.

The electrical connections to the O2 sensor may be resistive due to the oil that was leaking.
If you can reach it from above or below, see if you can spray contact cleaner on the electrical connections.
Avoid spraying it on the exhaust - use the spray straw to better direct it.

 

[odbcman]

Thanks for your thoughts on this.
The car goes into the dealer next month for it's yearly maintenance. Being the car is still under warranty for now I'm going to see what the dealer says as this has been an ongoing issue. I would expect I'll get the same response as last year - smell is normal and they can't duplicate P1179 fault. I'll post the dealer response in about a month.

 

[JimBmwi3s]

Maybe take it to a different bmw dealer.

 

[cpallenjr]

Doesn’t make sense you would get an O2 sensor code when the Rex isn’t running. I wonder if it is being stored after doing a maintenance self check? I would ask bmw to look at the O2 sensor wiring harness. Maybe it is touching the exhaust manifold.

 

[Arm]

Possible loose wire or cable that's always in contact with a hot REx? That cause the smell and also trigger the code? Just thinking of loud. What does that code indicate anyway?

 

[weajd]

Possible loose wire or cable that's always in contact with a hot REx? That cause the smell and also trigger the code? Just thinking of loud. What does that code indicate anyway?

Searching Google, the P1179 code indicates an O2 Sensor Signal Circuit issue.
Possible causes

• Faulty O2 Sensor
• O2 Sensor harness is open or shorted
• O2 Sensor circuit poor electrical connection

Because there is oil on the engine or exhaust somehow, the oil may be causing the circuit issue as well making it a more resistive circuit or shorting it out temporarily.

 

[RhodyDave]

I have a 2019 I3s with the Rex. Mileage is about 36,000. At least once a year I get code P1179 (O2 Sensor Signal Circuit Slow Switching??) while driving or when I just turn the car on and not using the Rex.

Two years the code P1179 occurred while driving and the Rex not running. I was close to a BMW dealership, so I decided to see what they had to say. All they did was turn the car on and off about 6 times and the code went away for about another year. They couldn't explain why it occurred. Any idea what this could be?

Last March I brought the car was into the BMW dealership for an electrical burning smell that occurred every time the Rex was used. I also let them know I was getting code P1179 randomly when the Rex was not being used. The smell according to the dealer was a leaking head gasket on the Rex. They replaced the head gasket but could not find out what was causing the P1179 code in the 3 weeks they had the car. I still have the burned electrical smell each time the Rex is used and now once again about a year later the P1179 code is back. I cleared the code with my code reader several weeks ago and it has not returned. The car is due for service in March 2024 and I'm going to bring this random code up again. The burning smell they tell me is just the heat off the Rex and nothing to be worried about.

Any ideas on code P1179 and is the burning smell normal when running the Rex? As a side note, the Rex is used very, very rarely on my part. If it's used by me, it may only be for a couple of minutes or during the normal 10-minute maintenance cycle.

FYI - My REx doesn't smell! But I run it for significant time, i.e.: a half-hour at a time. I've seen advice on this forum that best way to use it is to USE it fairly often. BTW, I've had my REx coded by CodeMyCar so I can run it when I want, not when CARB and BMW say I can!