Should be somewhere on the exhaust either before or after the catalytic converter
On the exhaust manifold where the runners meet.
It just has ( 1 ) oxygen sensor , before the catalytic converter ( upstream )
Bung in the exhaust manifold.
replace it..It should screw right in with a wrench.
The 1991 Pontiac Grand Prix oxygen sensor is located on the outside of the air filter housing. You will find the sensor on the back side of the air filter housing.
on a 91 blazer s10 4wd
It requires a special slotted socket. It will be cheaper to have a repair shop do it for you.
at answers.com
Knock Sensor On your 1992 Toyota Truck Previa 2WD (2.4L FI DOHC), the Knock Sensor is located: Front seating area, center, under engine cover, passenger side of engine, under intake manifold, mounted in engine block
It means the oxygen sensor is not giving an input to the PCM. Either a bad O2 sensor or a wiring issue.
Where is the temp sensor on a 91 Chevy astro
Where is crank sensor on 3.1 v6 91