my 03 has non working power locks, no response from pushing lock/unlock, no clicks, etc. I am trying to find some wiring diagrams for this system. I've already checked the fuse in the engine compartment, and am going to check the relays next. Would this prevent me from adding a new key? I was going to take the truck to a locksmith to have them add a key (only have 1), and thought if there's more to it, maybe it would also prevent them from adding one.

Neither lock/unlock switch works, and I can't try the fob, because it is bad too. Want to make sure the locks work before I get a key added or buy a new fob.

Edit:,
just checked for power at the driver door lock switch connector with key on and off, no power on any of the 3 pins to ground.

 

Fobs are a different system, they use the Central security module(CSM)
There is no actual connection between lock/unlock buttons and door locks, it all goes thru central security module
Looks to be TWO fuses in engine fuse box for the system, and one in cab fuse box
CSM is usually located above glove box, it is white or off white plastic box

Keys are PATS, passive anti-theft system, so you can get key added, door locks don't matter
If you get two new keys then you can add your own yourself if you lose one
You need two working PATS keys to add a third, or forth, yourself
But you still need the key cut

2003 door lock diagram below

 

Ron, thanks for the diagram, I'll check it tomorrow. good to know about the keys, I only have one, so I'll take it to a locksmith just for time's sake. (only $45, compared to $80+ for some locksmiths). I may eventually get FORSCAN, but I haven't seen a definitive guide for compatible adapters yet, and there are too many sketchy overseas sellers on Ebay & Amazon, rather buy in the US.

I saw some cut and spliced wiring, looks like someone wired in a horn relay and bypassed the factory one, no clue why (no aftermarket alarm or anything similar) maybe I'll find some other wiring that may be at fault for the locks.

 

I searched for Forscan ELM327 on Amazon and this one came up first I purchased it for my 03 and so far it works great. Our trucks only use the High Speed Can and not the Medium Speed Can, so I haven't been able to test if the MS Scan switch works. A few reviews state their switch was faulty but since we only need the HS Scan I'm not too worried about the switch working, I think mine works though because it tells me when I'm not in HS mode.

 

I've used this one to program PATS keys in my '99:

 

the 03 has CAN? I"ve been reading about diagnostics and the different busses, and I was led to believe these trucks were using PWM/J1850. That's at least what my scan tool says it is, and it is CAN compatible. I'll keep those 2 modules in mind. On another note, I did find a GPS/cellular fleet tracker in the truck, thankfully not hooked to anything anymore! That was quite a surprise.

 

Ok, checked the fuses and obvious wiring and can find nothing out of the ordinary. I think I'll leave it like it is if it won't affect adding a key. Does anyone have a link for a FREE full service manual in PDF form?
Is there any reason the previous owner would disable the central security module? I'd figure it would throw a code if you did, or prevent the truck from working. Just wondering if that's what someone did.

 

Ok, update on this, I now have FORSCAN and a compatible adapter, and I do not even see the central security module listed in the modules list, only PCM, GEM, ABS, and RCM. I'm guessing either the CSM is dead or was unhoked. this truck did come with factory power locks and key fob (have all paperwork for it) so it's not one someone added parts to. Guess I'll take the dash off and look for the module.