i have an OBD2 car which i need to get inspected next month in North Carolina. i dont have any hookups there so im gonna have to do it legit. right now my car is run n off an OBD1 P28 with uberdata. i also have a test pipe and i removed my secondary Or sensor (actually broke it so it dont even work)

im gonna see if i can trick the ecu into thinking its seeing a signal at the SO2 sensor. since i dont have an SO2 sensor, im gonna have to fool the ecu into thinking its get n a signal from the O2 as well as tricking it into thinking its heater circuitry is working. to solve the heater circuitry problem, im gonna place a 1K ohm resistor across the two SO2 sensor heater wires. this will make it think it's seeing a load.
then to trick the ecu into thinking its seeing a signal, im just gonna tap the Primary O2 sensor signal wire to the Secondary O2 wire by the ecu harness. so the same signal that is sent to the PO2 will be fed to the SO2 sensor. im not sure if this will work cuz both will have the same voltage and i believe the SO2 signal should read a slightly higher voltage. if it dont work like this, i'll place a resistor in front of the PO2 sensor so that the PO2 signal will read a lesser voltage than the SO2. i'll test it out anyways to see if it will work.

if that dont work, i might just build a LM555 timer circuit which generates a square wave output and feed it to the SO2 signal wire to the ecu.

 

I was wondering the same thing. Keep us an updated.

 

Your just going to store a dtc and turn your mil on and fail your smog test/bar inspection.If your ecu sees that your post 02 is reading the same and the pre o2, a hard fault will turn your MIL on since your computer sees it as your cat is dead.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Altizzy &raquo;</TD></TR><TR><TD CLASS="quote">Your just going to store a dtc and turn your mil on and fail your smog test/bar inspection.If your ecu sees that your post 02 is reading the same and the pre o2, a hard fault will turn your MIL on since your computer sees it as your cat is dead.</TD></TR></TABLE>

yea thats what i was think n. the secondary O2 sensor signal needs to have a higher voltage than the PO2. i will put a resistor on the PO2 sensor wire by the ecu side so there will be a voltage drop on it, so the SO2 will see a higher voltage signal. the SO2 wire by the ecu will be getting the full PO2 signal

 

just buy an o2 simulator.
like 20 buck i think

 

bucks

 

It's not just a matter of higher voltage. The ECU needs to see significantly less switching activity on the secondary than on the primary. Just feeding the primary voltage in, even with a resistor, will still have oscillations in the signal, still setting the CEL.

 

so then im gonna have to use a LM555 circuitry to feed a signal to the SO2 signal. just need to figure out what frequency to run it at

 

why not get an O2 simulator, the are about 50 or less

 

ya i here the o2 simulator works