My 2011 6.2 works just fine when temp is above freezing. When below freezing no crank. Lights on cluster work fine, no codes, power from battery to starter is good but no power to the small terminal when key in start position. Was cold the last few days and no crank at all. Took the wife's hair dryer and put under the hood for an hour or so. Started up like a champ. As long as warm starts, gets cold no crank. Ideas.

 

Certain things on vehicles can be checked with a simple test light.
If you are planning to help yourself with some vehicle electrical problems a good quality test light is a worthwhile investment.

What you could try is to clamp the ground clip of a test light on to the small solenoid terminal of the starter relay on the firewall or the small terminal on the starter solenoid
Then place the point of the light where you can see it and have the point stuck against any part of the sheet metal making good contact there. Now when you go to place the ign key in the start position ,if all is right the light should light , so you know all the connections are good up to that point. Let us know what you find, thanks.

 

Thanks Hanky, had wife turn key to start while using test light on small terminal. No power when cold outside ( below freezing). But power when above freezing.

 

If your vehicle has an auto trans, unplug the (MLPS) (,Manual lever position sw).,,neutral safety sw and check for any corrosion or poor connections there.
If that checks out
One thing we learn, depending on where you place the probe of the test light, you must make sure there is no power in that wire because, if there is a poor connection there and we only touched the post on the relay it would appear there is no power coming in.
The power comes from the ign sw on the lower steering column, goes to the neutral safety sw, if applicable, to clutch safety sw if manual trans, then to relay on firewall or to solenoid on starter.
Now you have some idea of the path it takes , it should help making checking a little easier.

If auto trans , don't forget to check if it works in neutral position , but not in park.

 

Thanks, checked the starter solenoid in like three places, no go. Crawled under truck to look at the neutral safety switch but I can not see anything like what was shown on the inter net. I can find the shift cable but there are no wires or anything like that attached to the side of the tranny. Is it somewhere else on 2011's.

 

Woops forgot to say it started after I heated engine compartment. Wierd.

 

Loose or poor connections can offer high resistance and as soon as the temp rises and parts expand , so do the connections, expand and now things work.

You could get lucky and find it right away or it could take some time.

You know the path the signal takes ,just start from either end and work your way to the other end and you will find the poor connection.