Where is the ect sensor located on a 03 chevy tracker

SOURCE: WHERE ARE THE KNOCK SENSORS LOCATED AT ON AN 03

Knock sensor can be found on top of the engine block, there are two you ´d have to remove the intake manifold to get to them,

SOURCE: 2001 Chevy Impala 3.8L

Thats on left rear of engine

SOURCE: '03 chevy tracker. no heat. scent of antifreeze

You need to have the cooling system/heater core tested for leaking. Those symptoms sound like the heater core has failed.

SOURCE: where is mass air flow sensor located on 2002

The mass air flow (MAF) sensor is an integral part of the throttle body assembly and cannot be serviced separately. For replacement of the MAF sensor refer to Throttle Body Assembly Replacement.

SOURCE: how do you check and change a camshaft position

The camshaft sensor wouldn't explain the clattering noise. But a timing chain would explain both. Clattering from a loose chain and the camshaft sensor code from when the chain broke and the camshafts stopped turning.