So I think I have two issues but I am not sure if they are connected. I own a 2008 F-150, base model, 4.2 with a standard transmission. I have 130k miles.

The first issue is the 0720 Code. My check engine light came on a few days ago about the same time my speedometer starting working intermediately. I had the code checked today after having my second issue which seems to be more serious.

The second issue is that I completely lost power while driving on the interstate. I was coming home from being out of town and was still about 4 hours away. All the gauges and clock completely stopped working but it was still driving, then the engine lost power. I got it to the side of the interstate and tried to re-crank....nothing! The emergency lights would not even come on.

My first thought was that the alternator was out and it had drained the battery. I got the truck towed to repair shop where they ran a diagnostic. It turns out the alternator is in great shape. It tested at 14.2 where I was told a good running range is 13.5 to 14.5.

The mechanic was just as surprised as me. They let it sit for an hour and it cranked right up. It was sluggish to crank but it was because the battery was drained. Once it was cranked it drove smoothly for them and they drove it around for 10-15 mins. (I rented a car to get home.)

One possibility that was given to me by a friend is that there is a short in the wiring harness for the speedometer. This could be causing the 0720 error and causing a bigger short with the electrical components. I don't know how probable this is but no one else so far has an answer.

So I don't want to drive the truck home 4 hours if its just going to stop working every little bit. I am not sure whats wrong with it and could use some help. Thanks all.\


FordMoose

 

Turns out the two are not related. The alternator has been working intermittently, slowly draining the battery. A once good battery was slowly killed over time until all at once they both stopped working.

Thanks to all who reviewed.