OBD2 not reading the PCM module

So I have a 1999 Ford F-250 Super Duty 2wd 5.4 pick-up. In the past week the truck will sporadically run really rough for the first few minutes like it is miss firing and then smooth mostly out, you still feel a slight miss fire every so often at a red light and I am only getting like 9 or 10 mpg. So I decided to hook up my OBD2 scan tool to figure out what is going on, only for it not to be able to find the PCM module. I have used this tool plenty of times on this truck before as recently as last month. Now every time I plug it in it will only read the SRS module and the ABS module, and it will list the PCM module as “Not Equipped”. I plugged the OBD tool into my 2008 F-350, 2004 Ranger, and a 2002 Dodge Ram and it reads the PCM in every other truck beside the 1999 F-250. So I am wondering if the OBD port is bad or is my PCM failing. Or am I missing something else entirely.

Well, the truck is running so the PCM is somewhat functional but the communication line to the PCM appears to have a problem. Is the check engine light on?

Maybe corrosion on the PCM connector? It is in the engine compartment, right? Unplug the PCM and check. They retry the OBD. Please post back with what you find and we’ll keep trying. This is an interesting problem.

Make sure the fuse in the OBD socket in the fuse box isn’t blown.


There is no check engine light, but I was trying to pull the live data from the the injector, spark plugs and O2 sensors.
The PCM it self is in the cab between the brake and parking brake pedals while the connector is in the engine compartment below the brake booster at the bottom of the fender well, so I will check tomorrow

all fuses are good