Is your 2002 trailblazer speed sensor located

No it would not ! you probably have a 2-3 Shift Solenoid (SS) problem !
You trailblazer has Vehicle Speed Sensor (VSS) located on the tail shaft of the trans . this sensor supply's info to the PCM for vehicle speed . Your trailblazer also has a Input Speed Sensor (ISS) if this were bad it would cause erratic shifts all gears ! Does your vehicle have a check engine light lit or any other type light like a yellow wrench or service vehicle soon ? Your best bet is to take it to AAMCO or some other ASE certified repair facility !

CJ, this is very common for the I6 engines in TB's and Envoys. You need a new fan clutch. Triple check the wire connectors first, located on the top of the radiator on the drivers side, make sure those are in tact first. Then replace the fan clutch. Might as well do your water pump and serpentine belt while you're in there.

On the Air tube intake halfway between air filter and intake!

See attached picture for location of temp. sensor, but that code has nothing to do with temp sensor. The speed of the fan does not agree with the commanded speed, you may have another bad fan clutch.

it is the sensor that is being pointed at in the cylinder head

Replace the crankshaft sensor. NO adjustment needed by software. Good luck and keep me posted, be glad to know your got your trailblazer running 100% again soon.

Hi.
The cooling fan speed sensor is built in inside the fan clutch.
If you have a code p1481 or similar , pointing at the cooling fan speed sensor, often you have to fix or replace the wiring , rather that the sensor.
Check that wiring has continuity, the wire to sensor must have +5V. Here an interesting website on trailblazer fan system.
Regards.

I think there is more than two. Either way, they are located in the exhaust system. The pre-cat sensors are in the head pipes, just below the exhaust manifold, and then there will be one right behind the catalytic converter. You will need a 7/8 inch wrench or possibly a special O2 socket.

Assuming you have a 4.2L engine here is the location.


Hope this helps out,
if so please rate my answers.
Brett

have autozone scan it for free could be multiple things wrong wheel speed sensors to abs pump does it come right on after starting? or do you have to drive it???