Resistor in OBD2 Diagnostic Connector


Original poster
Apr 17, 2012
Winnipeg, MB
I just got an OBD2 connector from the junkyard (from 2007 Envoy Denali) and I cut the wiring about where it merges into the bigger harness.
It has heavy duty black (duct tape?) wrapped around a few wires!
I cut the tape away by knife and there is a resistor crimped in between blue (pin 6) and light blue/black (pin 14). The resistor and wiring look lees than professional- I could have done much better.
What is this for?


Lifetime VIP Donor
Supporting Donor
Oct 22, 2015
Tampa Bay Area
The purpose of having that 120 Ohm Resistor in that wire harness is UNCLEAR . You should probe the DLC system you are working on at the Pin #6 or the Pin #14 Positions and at the Pin #4 and Pin #5 locations for Grounds in the 16 Pin DLC Under-Dash Interface. The NORMAL CAN-BUS System requires TWO - 120 Ohm Termination Resisters in the CAN-BUS HIGH-LO Network.

Their purpose is to Terminate the Circuit and Absorb any external electrical noise or voltage oscillations that can travel along the Network CAN-BUS and cause interference. There must always be TWO 120 Ohm Resistors present for the CAN-BUS to work.

However, whenever Testing for Resistance on the CAN-BUS at the DLC Port, the Normal Reading should only be around 60 Ohms when probing Pin #6 and Pin #14. This is because the Resistance between the Two 120 Ohm units gets HALVED if the CAN-BUS Network is behaving normally.

These Three Videos will instruct you how to Probe and Test the DLC for Power and Grounds and for the proper CAN-BUS Circuit Resistance using a Digital Muti-Meter:

You should investigate what the Resistor Ohm level is on that Odd Resistor you found and if you do NOT find one like it in the identical harness position on YOUR Vehicle DLC Harness... then you should NOT incorporate it into your DLC Repair Installation.

These Screen Prints come from the First of the Three Videos Linked above:



May 13, 2023
So need a 120 on bcm and on PCM? I've ran into these a lot, but I always see it as a single 120 at the OBD2 plug at dash and that's it

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