How To Make a 02 Simulator

How To Make a 02 Simulator


This article is intended for those who happen to own a performance vehicle meant for off-road use only. If you are here looking at this post to eliminate the check engine light in your vehicle, you should be looking at our DTC P0420 OBDII writeup, or our 02 defouler writeup.

This 02 Simulator is an advanced modification and can cause serious damage to you, your car or your loved ones if not done correctly. If you need help with your check engine light, there are safer alternatives listed above.

Have a Catalyst Efficiency Threshold Check Engine Light? This article is not for you.

Today we’ll be showing you how to wire your own secondary 02 sensor bypass, a unit that will send electronic signals to your ECU / PCM. This is in the event of your catalytic converter being removed or bypassed, and is meant for off-road use only.

DTC P0420 – Catalyst Below Threshold? Check our How To


Modifying your catalytic converter is illegal in many states, for more information check our legal exhaust primer. Do not modify your vehicle unless you have a full grasp on the laws you may be breaking. Check with your local state representation for further clarification.

When your off-road vehicle is annoying you with that ever present check engine light, and you want it gone you can do one of two things. Install a 02 extender, like this Weapon R Oxygen Sensor Defouler and check our article on How To install a Check Engine Light Eliminator.

Check Engine Light Eliminator

The 02 simulator we are putting together today best simulates a 4 wire oxygen sensor, and usually gets you in the right range for your check engine light to go off. If your off-road vehicle or smog exempt vehicle has it’s secondary 02 failing you can also use this method to completely eliminate the sensor all together.

If you are not comfortable with wiring or electronics, or unsure of any step in this process do not proceed. This process includes wiring in a resistor inline, and if not done correctly can lead to an electrical fire. Chances are your secondary 02 wiring and fuel lines are very close to each other, make sure you have a firm grasp on what you are doing.

Pro Street Online is not responsible for any damage to you or your car however directly or indirectly, please be responsible and perform this job safely and legally.

A standard 4 wire 02 sensor
A standard 4 wire 02 sensor

Shown above is a standard 4 wire Bosch connector, which shows you the color combinations and their usage for each pin. Here’s a few more color combinations that are common in many of today’s vehicles, if you don’t see your 02 color chart here leave us a message.


Parts you will need to complete this job :

1 – Mohm resistor
5 – 50ohm/12watt resistor
1 – 1µF capacitor

All of these parts can be found at Radio Shack or similar online websites that sell such components, and the job of wiring is very simple and straightforward.

First find your signal wire and ground wire, cut them and splice them leaving a good inch of exposed wire for you to wire your component inline. Solder the 1 mohm resistor inline between the signal and ground wires, and cap these two wires with the 1µF capacitor. 



Next we’ll need to take care of the oxygen sensor heater elements, or the remaining black wires in the Bosch example above. You will need a resistor of ~12 ohms, you can combine resistors to maximize the amount of voltage being bled off. These two heater wires flow about 1 amp of current, so you will need to account for at least 12 watts of current.


Strip the two oxygen heater wires and solder the resistors inline between the two wires, test this unit now by taping everything safely and putting your key to the ‘ON’ position. If you have not cleared your OBDII codes by now, you should clear the codes using a reader or reset your ECU by pulling the positive terminal on your battery.

You have now wired in your very own 02 sensor bypass! Congratulations!