What's the p-code?

 

P0153

 

I'm not sure where you got that code description but a more accurate description is "P0153 BMW - O2 Sensor Circuit Slow Response Bank 2 Sensor 1"
I'd be looking at replacing your pre-cat O2 sensors

 

If the vehicle has over 100k miles and the Pre-cat O2 sensors are original, which they most likely are, I would replace the Pre-cat O2 sensors.

BUT, I would not expect this to be the end of the error/fault code.

My experience is that lazy/slow response O2 sensors RARELY trigger any codes. I typically only see O2 sensor codes when heaters fail. So take this for what it is worth. You may need to dig much deeper to look at fuel mixture control problems due to vacuum leaks and/or restricted exhaust.

 

Thank you. I've done a smoke test on the intake. I will be checking for exhaust leaks as well. My other precat sensor threw the same fault code once last week as well. Odds of both going out simultaneously seem slim to me. I do have a fault for my auxiliary water pump, that's the only thing I can think of being related to the heater.

 

Also I noticed my secondary air pump hose was brittle and probably leaking and my egr valve is missing it's gasket. Going to replace those as well.

 

I am unaware of the E46 having an Auxiliary Water pump, is the car you are asking about an E46 or another model?

These cars do not have an EGR valve, what you are referring to is the SAP system Kombi valve located on the front of the cylinder head. If this valve is missing the gasket, then this could be allowing excess air into the exhaust ports and could very well be the source of the source of the current O2 sensor codes.

How many miles are on this car?

 

I am unaware of the E46 having an Auxiliary Water pump, is the car you are asking about an E46 or another model?

These cars do not have an EGR valve, what you are referring to is the SAP system Kombi valve located on the front of the cylinder head. If this valve is missing the gasket, then this could be allowing excess air into the exhaust ports and could very well be the source of the source of the current O2 sensor codes.


How many miles are on this car?

It's a 2002 m3. 134k miles. The auxiliary water pump has something to do with the heater referring to the cabin heater not o2 related. I ordered a new hose and gasket this morning. I noticed it was missing when I removed my heat shield to inspect the sensors.

 

So the M3 has the Aux Water pump for the heater like the E39 and some other models. I am aware of the Aux Water pump system on the E39 M5, have not dug super deep into the M3 inner workings, but I have never seen the Aux Water pump on a non M E46. I know the Nav Radio would usually be required for the system to operate.

Get the gasket for the Kombi valve installed and then see what happens with the O2 sensor codes, but you need to replace the Pre-cat O2 sensors if they are original anyway at this mileage.

 

Ok thanks