E34 without O2 Sensor have 1221 Error Code

[shogun]

no need to find a factory cat. A universal steel cat is better, takes less space and even might give some more HP.
Just search in the net for Universal High Flow Catalytic Converter

But I assume in the Philippines it does not matter if there is a cat installed or not?

Then there is another option: Oxygen Sensor Simulator
Oxygen Sensor Simulator

Or the version Dave made, maybe the easiest, welding a O2 sensor thread into the pipe.
Thread size I believe it is M18 x 1.5. Or use a thread chaser and make the thread into the pipe.
Go to your local parts store and ask for an O2 sensor thread chaser.

[redled]

Yes I will copy Dave's version anyway you are right there is no restriction here about environmental compliance.

[Dave M]

Not sure if you covered this, but you will need to find the wiring harness that the new O2 sensor will connect to. If I recall correctly, the end of mine is clipped somewhere below the starter.

Dave

[632 Regal]

He doesn't have original O2 wiring? It must be stuffed away somewhere. In general if you want to ad 1 O2 sensor it would go right before the mufflers. If you have 2 O2 sensors the reading one goes right infront of the muffler and the other after. The secondary O2 sensor just has to have a reading different than the first so it wont trip the CEL code.

[redled]

There is a threaded plug for 4 wire sensor below the starter.
Can I use any brand of sensor, is the reliability with different brand the same?

[Tiger]

Any brand will do... just make sure you get the one with wire harness on it rather than universal.

[genphreak]

They can be broken if the box is dropped so it may pay to use a half-decent supplier.

Avoiding universal is important, don't go soldering wires, they are stainless steel and can get hot enough to melt any type of solder. Hella and Bosch make them with the required (about 35mm diameter) Bosch 4 wire plug, just search the web by part number.

If you have a bung already in your pipe (is that what you meant by under the starter?), you will need to drill it through and/or tap it. Beware as you may hit stainless steel. Whatever happens, beware welding- you need someone good to weld stainless engine pipes. If any part you need to weld is rusty and does not clean up well, the welding will be challenging (stainless is seldom quick to rust though)...

[genphreak]

no need to find a factory cat. A universal steel cat is better, takes less space and even might give some more HP.
Just search in the net for Universal High Flow Catalytic Converter

Are you sure, Erich? On many sixes people seem to end up using a single large bore universal rather than the two that BMW fit- and the BMW ones are wider and lower to fit the tunnel without hanging down. They are also better insulated than the Universal ones. If you use one and it isn't shielded as well, it could do things like cause grass fires if you leave your car on the side of the road one day...

[Dave M]

They can be broken if the box is dropped so it may pay to use a half-decent supplier.

Avoiding universal is important, don't go soldering wires, they are stainless steel and can get hot enough to melt any type of solder. Hella and Bosch make them with the required (about 35mm diameter) Bosch 4 wire plug, just search the web by part number.

If you have a bung already in your pipe (is that what you meant by under the starter?), you will need to drill it through and/or tap it. Beware as you may hit stainless steel. Whatever happens, beware welding- you need someone good to weld stainless engine pipes. If any part you need to weld is rusty and does not clean up well, the welding will be challenging (stainless is seldom quick to rust though)...

He's referring to the plastic threaded O2 wire harness he needs to connect with the new one. He may need to use your welding advice further downstream.

[genphreak]

Duh! Silly of me...