I just replaced my knock sensors on my 2001 Chevy Tahoe 5.3.. But now the codes reads P0300 and 0405

SOURCE: knock sensor location

HI, click the link below to be directed to a full diagram that will show you the actual location of the sensor. 718 will be the actual sensor to extract and 739 is the mounting screw for the KS.

KNOCK SENSOR DIAGRAM

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: 2003 Tahoe, 5.3 liter vortec flex fuel. Engine

this is a comon problem on chevy 00-06 models a computer ground ,it seems ok at sight but inside it's just holding a few wires ,get under the car on the driver side passenger there you should find a two ground wire goin to the block a big, and a small ,the small one gets coroded try to fix it and let me know how it goes ok.

SOURCE: how do you replace the knock sensor on a 2005

The knock sensor should be on each side of the engine block. These are single wire connectors and require no special tools or tricks. Simply unscrew and install.

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SOURCE: replace knock sensor on 2001 chevy 4.8

You have two knock sensor's, both sit under the in-take magifold on top of the engine, you will have to remove injector rail and in-take.