Try wiggling the trigger wire at the starter first. The connector at the end likes to get corroded and the wire itself can rub through on the A/C lines on a diesel. Both are fairly easy fixes. The starter is on the drivers side of the engine, at the bottom. You can sort of reach it from below/behind.

 

Starting off a bad morning... 2008 GC CRD does not crank. Dash lights go out when place the key in start position.

This sounds more like a drained battery or a loose battery connection. I would start by verifying battery voltage, then checking that the battery terminal connections are tight and free of corrosion. Then check that the ground coming off the battery and connecting to the body is tight and clean.

If that's all good, then look at the starter. Driver's side bottom of the engine, it can be accessed through the driver's side wheel well. The connector on the end of the yellow wire (from the ignition switch) likes to get corroded/loosen up. You can replace it with a standard female spade connector, preferably a weatherproof one, and put dielectric grease in the connector

 

Thanks underscore... i wiggled the Yellow trigger wire it and removed it once or twice. No luck. It looked fairly clean anyways.
I ran a new wire to this terminal and it barley cranked over. BTW, dropping the driver fender liner back end gave pretty good access to the started. I also removed the drivers front wheel.
Not sure what made me go to the ECU /ECM but since i washed her down anything is possible. I removed the battery and battery tray to access the ECU. I removed the 2 connectors and tapped them downward to clear out any crap and reconnected. Put it all back together and BINGO, she started.

this guy took the starter out (but note he is Aussie and says the starter is on the passenger side...that's the wrong side over here!!! HAAA) - meaning they drive on the other side
http://www.ausjeepoffroad.com/forum/showthread.php?t=124191&highlight=Starter

 

My buddy had similar problem. Ended up being crankshaft position sensor