have 09 colbalt with downstream o2 sensor bad. replaced with cheap aftermarket and no good, I can see hi spike voltage from it. What is the recommended vendor for the aftermarket o2 sensor?
The oem looks like about 88. that's a bosch. before i spend that like to know if there is a cheap aftermarket one.

Oxygen Sensor-Actual OE Bosch 15388

 

With something like a sensor, I tend to stick with OE parts. In my experience, cheap electrical parts tend to suck... as you have already found out by ordering a cheap aftermarket O2 sensor.

Just get the OE sensor.