Thanks very much. I do appreciate your help. Doug

my o2 sensor plug has a black wire, grey wire and two white wires, then at the plug they turn into the following:


black goes to yellow
grey goes to black
white goes to green
white goes to brown

on a 1999 318TI

i read the following on pelican article:

Lastly, with a 4-wire oxygen sensor, the output signal works in a constant loop, essentially, the fuel injection computer sends a signal to the sensor, and the sensor then sends the signal back to the computer. This is achieved by having one wire carry the signal to the sensor, and then another wire carries the signal back to the fuel injection computer. You also have a wire carrying 12 volts to the heating element, and the last wire is the ground for the heating element. (pic o2_sensor_diagram_4 jpg) With a 4-wire sensor, you will need to measure the voltage fluctuations between the two signal wires. To do this, start the car and let it warm up. Next, disconnect the oxygen sensor and measure the voltage between the wires. Now take off the oil filler cap to simulate a rich running condition. Watch the voltage, if it begins to fluctuate rapidly, then the sensor is good and you’re done. If it stays the same, it’s probably fried.

The two whites are heater wires the black is ground and the grey is signal. The O2 sensor is a voltage generator. It gererates voltage by the amount of oxygen in the exhaust. At least that is how I undersand them to work and how my simulator works.

If not how could the voltage fluctuate or be present at all if it is disconnected from the harness? Also running a O2 sensor in the exhaust stream without the heater wiries connected is a great way to burn it out real fast, just an FYI.

After speaking with you on the phone I think you have a wire mis-labeled.

O2 sensor wires to tap into O2
White = Heater
White = Heater
Grey = Signal
Black = Ground

After plug O2 wiring to DME cross-over wiring to tap into DME wiring:
Black = Ground pin 46 DME
Yellow = Signal pin 19 DME
Brown = O2 Heater Ground pin 30 DME
Green = Connects to all red/white wiring 12 volts in ignition on key position

SAP Simulator
 

So i installed my secondary air pump simulator in the car finally a few weeks back, i checked the simulator with multimeter for correct settings, wired it in correctly with help from johnboy here, i dont get any codes for o2 sensors and car runs great as usual, so i know its wired in properly, however i still get the check engine light on at right about 40 miles after scan and reset, whcih is how many miles have to be driven for the SAP system to be ready in the computer, in my 318ti. Its the only code in the ECU and i have reset it three times, same thing every time, at about 40 miles driven after scan code comes back, any ideas?

Sap Simulator need to put out voltage of 200mv on red wire to DME when the SAP is active. I think your mv is too high so the DME thinks the SAP is not working. It is very picky and needs to be set at 200mv. Are you sure the SAP is active when you first start the car. It should only run for 30-50 seconds then turn off. If the unit is not working the code should not show until the next time you have a cold start. Nothing about 40 miles into a drive, I've driven 250 miles with no code then the next cold start gave the code when the unit was not working...

I know of at least 25 units with no issues.

as for the 40 miles the ecu doesnt have the sap ready untill 40 miles after the last code reset, i dont know why this is, but this is why they tell you that if you recently had your cars codes deleted, you need to drive for a while before you take it into emmissions otherwise emmissions computer will tell you that your systems onboard are not ready, this is true because this is my problem, anyway i guess my only option is to try and check the mv readings on my module agian. By the way the check engine light would be triggered and is triggerred on the next cold start, the only difference is that it wont if i just deleted the codes, untill the sap system becomes ready in the computer, (40 miles driven after deleted SAP code on my car) only then is the computer able to check it. Will update after i recheck my module. thanks.

once agian i want to say thanks to johnboy for helping me, i figured out it was the voltage regulator that was no good, i rebuilt the simulator and realized the old voltage regulator was not putting out the 5 volts as required. Will be deleteing SAP check engine light code again and will test drive and see what happens.

UPDATE:
 

well after remaking the simulator with a working 5 volt regulator, i realized that the simulator is still not turning on (it does turn on when connected directly to the battery instead of using the old SAP wires) (i installed a red led to be able to see too), so got out the multimeter again and went fishing, found that the original GROUND wire going to the SAP was not grounding the whole time!

I moved it to another place and simulator is now functioning, well see how it goes after driving the car for a while.

By the way, if I made the simulator again i would do the following in addition to installing a 12volt LED on the positive lead for SAP, i would also install a different color led on the 5 volt regulator to make sure its working and if possible another color led to show either that the simulator is feeding data to the ecu or that it is off, therefore sending data directly from o2 sensor to ecu.

And better yet install all three leds inside the car next to the ASC-T switch, so i can see it inside, instead of having someone else look under the hood, or me getting out of the car to check. But now im just getting fancy!

So I got all the parts for this mod (and extras because I suck at glueing stuff together) and my BMW buddy asked me if we could do it for his V8 as well. I know the v6 needs the dual bank version, would the v8 need 3 banks?

Thanks in advance. Sorry I forgot to ask him what series this is for.

Where do I locate the DME and O2 sensor from the car to connect the Grey DME wire and Blue O2 sensor wire?
Do you have pictures to show how the wires are connected from the built simulator to the car DME and O2 unit?

Find the upstream O2 sensor. Cut the signal wire and patch the Blue wire to the wire you clipped leading to the O2 and the Grey to the other end that you clipped that would lead to the DME.

When the SIM is off it will connect the clipped wire and your O2 work normally and when the SIM turns on it sends a 200mv signal to the DME tricking it so it thinks the air pump is working

John,
do you think this will work for the 6 cyl motors as well?

I think John already answered that....

My car is the 1997 BMW 328I. There are two O2 sensors. They both have the following color code: Black, Red, Yellow and White. So,
How do I know which O2 to tap into because there are two O2 sensors?
Which wire COLOR is the signal for the DME?

Bump for a great article~ :cool: