I'm kind of at the end of my ropes here. I recently purchased a 1987 S10
Blazer 4WD with a 2.8L TBI engine. The Service Engine Soon light keeps
coming on and the code is a 13 (o2 sensor).
So far I've replaced the O2 sensor and the temperature sensor. When that
didn't help I hooked up an oscilloscope to the O2 sensor to check the
voltage level which was around 1.3 Volts (one point three volts) From what
I can tell this reading is WAY out of range.
The next step was to hook up the laptop to it via the ALDL port and get some
readings. The O2 sensor voltage reading according to the ECU was 0.455
As far as I know, this could only mean one of two things. Either there's a
problem with connectivity to the ECU (i.e. broken wire) or the sensor isn't
grounded properly (1-wire sensor) and the difference between the sensor's
assumed ground and the ECU's ground is .5-.6 volts.
So I was wondering where I could find the ECU in this thing to trace the
purple O2 sensor wire and make sure it has continuity. Any other ideas are