Juan7

RE: Dodge Truck and Jeep - Engine Control Modules supporting both SAE J1850 and ISO 9141-2 Protocols.
Chrysler LLC has determined that certain Dodge truck and Jeep vehicles have an engine control module (ECM) that will respond and communicate to generic scan tools or Inspection and Maintenance (I/M) equipment with either SAE J1850 (10.4 VPW) or ISO 9141-2 (K-line). These vehicles were intended to exclusively support J1850 however the earlier K-line protocol support was mistakenly not disabled. These ECMs will communicate on whichever protocol is tried first. The same OBD information (e.g., readiness status, fault codes, commanded MIL status, etc.) is available from the ECM on either protocol.
The “dual protocol” support may cause an issue in I/M where programs are expecting a specific protocol to be supported for these vehicles and/or comparing the supported protocol with other like vehicles or past inspection records of the exact same vehicle (e.g., for fraud detection). The protocol used will depend on the order which the inspection equipment cycles through the different protocols during initialization as well as when in the process the inspector connected the equipment.

Dodge Truck Applications with "JTEC" ECM communicating on both J1850 & ISO9141-2
2003
Ram Pickup
3.7L V6, 5.9L V8