[dzenno]

If I were to put in a procede into someone's car that hasn't been modified yet and this procede had a built in o2 simm, would that throw codes?

[bolty]

If by o2 sims, you mean the resistors, then yes it did for a FOAF

After about 150 kms, got CEL. Removed o2 sims, cleared codes, never came back.

[maui86]

i did the sims via shivs DIY and never got codes, lights or anything. completely stock. had catless DP's on the way so i figured i'd do it before hand. sold the rev1 unit and bought the rev2, then installed the rev1 on a different 335i with stock dp's and no issues. i guess since one guy had issues you wont know till you do it

teri

[scalbert]

Yes it would. Take a picture, high res, of the harnes and I should be able to show you were to cut. It would be just one wire and could be hooked up again later.

[bulldog_yyc]

I had my o2 sim on my jb3 harness with the stock o2 sensors & downpipes and it did not throw a code or behave any differently.. except the jb3 which made the car pull like a raped ape

[gian335]

same with me turkish....i had bms o2 sims for about a month with stock dp's, didnt throw any codes.

[zsapphire7]

i did this and it didnt throw codes for a thousand miles +... I guess it depends on how strong the o2 sim (resistor) is.

[scalbert]

That tells me the ability fo the DME to detect a clogged cat is limited. Good to know though.

[bolty]

These are the relevant codes pulled not long after the CEL:

2CA9:
2CA9 Lambda probe heating behind catalytic converter 2, function

2CA8:
2CA8 Lambda probe heating behind catalytic converter, function



This was the DIY hack that shiv posted; 2 cut wires, and 2 resistors. This was reversed by simpy cutting out the resistors, and patching back the 2 wires.

[bulldog_yyc]

depends if the voltage divider was connected properly, the resistors themselves (some have 10% tolerance values) and the ranges the ECU will accept as valid test values

[scalbert]

Originally Posted by turkish335

depends if the voltage divider was connected properly, the resistors themselves (some have 10% tolerance values) and the ranges the ECU will accept as valid test values

Clip the ground reference and the whole concern is moot.

[bulldog_yyc]

Originally Posted by scalbert

Clip the ground reference and the whole concern is moot.

so the ECU will read as open? Whats the point of the voltage divider then?
Not saying you are wrong, but from my understanding, the O2 sensors output a range of voltages during normal operation, which is proportional to the chemical/thermal properties of the exhaust gas?

[scalbert]

Originally Posted by turkish335

so the ECU will read as open? Whats the point of the voltage divider then?
Not saying you are wrong, but from my understanding, the O2 sensors output a range of voltages during normal operation, which is proportional to the chemical/thermal properties of the exhaust gas?

If you have hardwire voltage dividers but do not need them, clipping the ground wire would make the sim irrelevant.

[bulldog_yyc]

Originally Posted by scalbert

If you have hardwire voltage dividers but do not need them, clipping the ground wire would make the sim irrelevant.

gotcha, I thought you were talking about just clipping the voltage reference rather than building the divider to construct the sim itself