I just went through this type of problem with an '06 diesel. There is a bit of electrical troubleshooting needed to pinpoint the problem.

From your description, there is no click when you turn the key and the engine does not crank. Try this with a door open and see if your interior lights dim at all when you turn the key to start. Any dimming and the battery cables/connections would be the problem.

If it is a no click, no crank condition, any one of the following can be the cause.

(1) Fuses - check your owners manual for the fuse leading to the starter relay and to the PCM. Either fuse will cause this problem.

(2) Starter relay - you would need to pull the starter relay (your relay is probably in the junction box in under the steering wheel) and see if voltage gets to the relay when you turn the key to the start position. If you have voltage to the relay then you know the ingnition switch and the transmission range sensors are OK. The relay itself can be checked with an ohm-meter, but they are cheap enough to just replace.

(3) Ignition switch - check for voltage at the starter relay. If no voltage, pull the fuse leading to the relay and check for voltage on the input side of the fuse. If no voltage, disconnect the connector leading from the ingition switch and check there. (You will need to get the electrical manual for your exact model year truck to get the right connector and wire color ID).

(4) Starter solenoid/starter - check for voltage at the starter solenoid positive terminal (between the terminal and ground) when the key is turned to start. (Need two people for this one since the solenoid is on the starter). If there is voltage at the solenoid, then the starter/starter solenoid is the problem and a new starter is needed. If no voltage then voltage is not getting to the starter and the problem is in one of the above steps. You can run a jumper cable from battery positive to the starter S terminal to verify the engine cranks (take care with this step). If the engine cranks then the starter is OK. If the ingnition key is in the on position, the engine will start when jumped.

(5) PCM - This involves taking a resistance reading between the ground side of the starter relay and ground. (The PCM provides the ground side of the starter realy). If the resistance is high, the PCM could be bad.

There are other checks that a professional would do, but this should get you started.

Lou Braun