rear o2 sensor w/ wb in GTO

[goatkart]

ODD question i know...

but im messing with sending the LC-1 signal through my rear o2 sensor....

and when i set the voltage to .59 volts.... the lc-1 is rock stable putting out .60...

however, when hptuners reads it from the computer... as soon as the cooling fans come on, the voltage jumps from 600mv to 710mv, and depending on whats cycling on and off, the voltage swings all over hell....

i could watch it happen using the scanner and turning the fans on and off...

the voltage would go up, then go down, then on then up, then down right along with me cycling fans...


am i scanning the wrong pid that im not getting actual voltage... or is there something going on that i dont see...

and yes, i confirmed the actual voltage coming from the harness never changed... in both conditions it read a solid .60volts from the harness... it ONLY changed at the scanner..

HELP ME!

[50FordF1]

Sounds to me like you may have a problem with the ground wires. Perform a quick test. Try adding a ground wire in parallel with the fan ground leads. One end to the fan the other end of the wire to the negative terminal on the battery, then try a few spots on the chassis. Use as heavy gauge of wire as possible for this test. With each ground point repeat your scans and see how the voltages have changed. Dont forget to add a heavy 4 AWG ground wire from the engine to chassis and another from chassis to battery.

It is not uncommon for voltages anywhere from a few 100mV to over a volt to develop on ground wires that are not a heavy enough gauge. As the current in the wire increases so too does the voltage drop. This can cause all sorts of strange problems when trying to monitor sensors.

Use a voltmeter - connect one side to the negative terminal of the battery. Take the other lead and probe different ground wires around the vehicle. Do this with minimal load then repeat with the headlights turned on, fans on, heater on, etc. Ideally you would read 0 volts all the time, but this wont be the case.