On wednesday i was going to Walmart with the old lady and bing the check gauges light came on. What do you know my charging system is not charging reading 0v on the gauge. When i get there i cycled the key three times and got the code p2502. taking the mileage into consideration i decided to replace the alternator. Fired the truck up charging at 14v on gauge, check voltage at batteries and from back of alt,ok. drive the truck down the road bing charging system 0v again!! now im ******, scan it p2503 this time (CHARGING SYSTEM LOW ERROR). Now i got my hands on the repair procedure for this code, but its a little confusing. what i need to know is if the ECM is the module mounted on the firewall or on the engine block, and a connector pinout of the ecm connectors because its telling me to test the " field generator coil and field generator driver" for a short to ground.
The possible causes for this code according to the diagnostics I have are field coil/driver short to ground or failed ECM.

I cleaned connectors at alternator and applied di-electric grease, cleaned battery terminals, di-electric greased and ensured they are tight, removed cleaned and greased chassis grounds i could find. Load testes battery both new and old school ways and prove to be good.

My truck is an 03 ram 2500 5.9L STOCK no mods at this time its my daily driver and need to get it going again please help! thanks

 

How old are your batteries?

Read THIS thread and see if it helps at all.

 

Warmachine! This is Julio. I just posted a question similar to yours. My oil press. gauge quit without any check engine light. Mechanic thought it was the sending unit. However, it is a failed ECM. I have a 2002 and it is mounted on the side of the engine block. I wonder what genius thought of mounting an electronic component in this environment! Anyway, a new one is $1100.00 plus and they aren't very plentiful. I had asked in my thread for advise on some way to avoid this expense.

 

I dont think that the posted thread relates to my truck because i already had it flashed to latest update a couple of months ago and mine is not star scan compatible it has to be used with DRB, meaning i cant flash to the posted flash #.
Are you guys sure the ecm is the one mounted to the block? Anybody have pinouts? It would be very helpful and greatly appreciated. thanks for the input guys

 

Ive been researching but some verification would be nice. From what ive read it is possible to replace your ecm with a used one but the dealer will need to program the skim and vin information from your into the used ecm then it will work other wise it will just start and stall. This sound right to anybody?

 

I FIXED It guys! The moral of the story is make sure the test equipment you use is in good condition. Got my hands on a midtronics tester, tested my batteries passenger side said Replace battery, and the driver side said unstable. swapped in two new batteries TA-DA! she's mint, did full field test with scan tool every things good now.
In case your wondering the other battery tester said low recharge for both, so don't be fooled, and they stayed in the green and held with the old school load tester? beats me all i know is its fixed and relieved
im
thanks for the input guys, hopefully this will help somebody else in the future.