If the engine starts and runs, and all your gauges work, the PCM is doing pretty much what it is supposed to, and points to a problem with the port itself, or, the wiring thereto.

What year is your truck?

 

97 ram 1500 cc 4x4 5.9 v8

 

Had the motor every been replaced? Someone could have done a hack job on the wiring

 

no all is orignal worked fine till about 6 mo ago

 

Grab the 96 service manual from this thread. Start checking the wiring for your com port.

 

I believe US Federal Law states that starting with OBD II, the port has to be under the dash on the driver's side of the vehicle. A friend I grew up with, who is ASE Certified, stated that to me at one time and followed up that he HATES working on Volkswagens as VW buries the port deep under the dash.

 

Wouldn't surprise me. It HAS been a while since last I worked on a ford.....

 

GM usually fuses the obd 2 port.The tipoff is when the cig lighter doesnt work and you cant get ecm data.Dont know about dodge,but its worth a look

 

The data link is set up with ISO 9141 protocol to receive/transmit data to/from the pcm. Pin 4-5 are grounds respectively and are obd2 required. Pin 4-5 can help troubleshoot many problems use a DVOM. Pin 7-15 is the k-L or high/low lines to receive/transmit data. ISO 9141 needs a wake up call back to the pcm on the low side inorder to receive/trans data and some scanners have a hard time with this.

 

i have used 5 diffrent scan tools
disco the battery for 24 hr no change