This BenchForce OBD-II Pass Through Device with 120 Ohm CAN Termination adapter is a simple device that allows you to add 120Ω electrical resistance (termination) to a Controller Area Network (CAN) bus. OBD-II is the standard 16-pin diagnostic connector found in most vehicles. This adapter connects between your OBD-II port and your OBD-II communication device. It provides the correct CAN bus termination necessary for reliable data communication and can help resolve error messages such as "no communication" or the HP Tuners Detect Protocol Failed error.
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When would I use something like this?
You would use this device when trying to communicate with an Engine Control Unit (ECU) that does not have internal CAN bus termination. A 120Ω terminating resistor must be on the network for CAN-based communication to work. For example, some General Motors Transmission Control Modules (TCMs) lack an internal 120Ω resistor, though the T42 and T43 models have one. Without the correct termination, you can't establish a connection. Note that our current PowerBlock Switch Assemblies include a 3-way ignition switch that enables 120Ω CAN termination when needed.
Here's a more specific example. If you are using a Holley EFI Terminator X Max Transmission Kit—GM 6L80/6L90 (p/n 558-499), you will quickly notice how limited you are with TCM programming. Without a device such as this, you won't be able to communicate with the TCM using a programming interface like HP Tuners MPVI3.