2002 Chevrolet Tahoe LS 5.3L no start faulty ignition switch

Truck problem question:

I am confused about the right way to test a no start on this 2002 Tahoe no start which relates to the ignition system. If during the no start and you have checked the fuel and spark and both of them are gone, is it the crank sensor or the ignition switch?

ATS Adviser:

Here are simple tests to determine which of the 2 system is the culprit:

2002 Chevy Tahoe crank sensor:

Go to the sensor itself and see if you have fuel signal during cranking (it must show up at KOEO).You need a scanner to see the fuel data during cranking. Next, using a dvom, check the crank 5 volt vref signal at the crank sensor if present, you can verify that also in other sensors like TPS, mass or map sensor. Note: once crank sensor is buggered up, it will not work anymore.

2002 Chevy Tahoe ignition switch:

Trace the ignition supply wires going to the injectors, relays. Use a head light bulb as load connected between power and ground supplies. Bright light is OK , dim light means the wiring is shorted. You can also use a DVOM and measure the power/ground supplies. If you have the wiring diagram, you will notice the injector power supply wires get it source from the fuse whereas the ground wire signals are sent by the ecm.

Shown below is a typical 2002 Chevrolet Tahoe power wiring:

2002 Chevrolet Tahoe power wiring

For more details, you can get a complete wiring diagram for this vehicle from most parts store when you buy parts or get it free online when you join ATS.


It was the ignition switch for this no start problem!. Found it by checking the feed going to the ECM module and relay, both were not available at KOEO. Verified by supplying direct power to the injector output wire of the ignition supply which was supposed to power up the injector power circuit and it started! It is easy to see what's going on once you see the injector circuit wiring diagram with the ecm. This is great and thanks!

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