I have also found this on my computer and I post it here for you who need to cut cost.
I have not personally built one of these so I don’t know if they are good or else.
I have built one similar to this but it had an adjustment potentiometer and it did work.
I may post it if anyone is interested. Let me know with a comment.
How to build Your Own Oxygen Sensor Simulator!
The rest of the page shows how to build an oscillating signal generator with just the right frequency and voltage to fool the ECU.
It is based on classical astable operating mode of 555 timer, so nothing revolutionary there.
However we spent few days of fiddling and testing to get the right behavior.
The parts will cost about $15 – $20 from Radio Shack. It’s not that hard to build if you have some experience.
Click to view or right click and save as to download.
Components:
R1 100 K Ohm
R2 1 M Ohm
R3 100 K Ohm
R4 10 K Ohm
C1 4.7 uF
C2 22 uF
D1 1.7v@20mA LED
D2 1.7v@20mA LED
Hookup:
Power source Ignition, or to the ECU PIN #1
Ground One of the ground points or ECU PIN #80
OUT ECU PIN #47 (disconnect the O2 sensor wire)
Catalog part numbers from Radio Shack stores:
(NOT for their online system)
276-309 5mm wide angle red led 1.7v, 20mA
276-1723 The 555 programmable timer
276-1995A The 8 pin socket for timer chip. It makes soldering safer and replacement easier
276-150A Generic Perf PC board
64-3052A Pack of blue tap-in connectors
278-1225 Stranded wires (black, red and green)
270-1801 Small black plastic project box 3 x 2 x 1
272-1024 Capacitor, 4.7uF
272-1026 Capacitor, 22uF
Additional notes:
If you use different flavors of 555 timer chip or LEDs with different parameters
you will need to readjust the values of R4 and R2 to get the interval and output voltage right.
Don’t attach it directly to the ECU right after assembly.
Instead attach it to the battery and check the output.
You should get approximately 0v/0.7v flipping about every 3.3 seconds when the car is not running,
and 0v/0.9v when the car is running. The current should stay below 10mA.
One LED should be always on whenever the power is supplied.
Another LED indicates when the output signal is high, so it should go on and off with the signal.
When tapping the ECU wires, triple check everything before hooking up the oscillator.
The power source should read 0v when the key is removed,
about 12.6v when they key is at ACC and about 14.3 when the alternator is running.
The resistance between ground wire and the body shield of the ECU should be 0 ohms.
And it would be best if you run the car and monitor the voltage of the original
oxygen sensor wire before cutting it to make sure you have indeed got the right one.
The resistance between ECU PIN #47 and ground is about 1.3 to 1.6 M Ohm.
The original sensor should still be dangling around, or plugged into the exhaust pipe.
The reason is that ECU also monitors the resistance of heater circuit inside the sensor.
If you want to COMPLETELY disconnect it, you will need to measure the resistance of the
heater circuit and install the right resistor between ECU PIN #72 and ECU PIN #31.
Anyway, there is no need to do it if you just leave O2 sensor alone and only intercept the oxygen signal wire.
NOTE: I would try just tapping into the wire before cutting it and connect
to it to test out this setup. It should work this way also.
Above testing and precautions will prevent you from frying the ECU and spending major $$$$.
Anyway, no one assumes any responsibility if you still manage to do so. So Check and re-check!
NOTE: This is not one of mine, these guys below are credited with this and whom ever I got this from.
Thanks to:
Mohd A, providing documentation
Nick P, running the www.mkiv.com list,
Oolan Zimmer, encouraging (and testing)
Steve V., RadioShack part numbers
Tovar Millhollin, testing the prototype
Related posts:
- Build A Map Maf Sensor
- Build Your Own EFIE
- Fuel Injected Vehicles
- Common Engine Sensors
- How Fuel Savers work
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Posted under Efie
This post was written by Michael on October 30, 2008
