How To Make A Dedicated Bench-Top Instrument Cluster Bi-Directional Electrical Test Harness

car diagnostic tool

I’m back with what I consider to be A VERY BIG DEAL in the way of How To Make A Dedicated Bench-Top Instrument Cluster Bi-Directional Electrical Test Harness that will work with ANY Scanner that has the BI-D Capabilities. FINALLY… Somebody in the GM Instrument Cluster Repair Business has taken the time to decipher the GM 24 Pin Cluster Connector interface to the J-1850 Female OBD2 (Auto Chassis Under-Dash) Connector.

Armed with this information …and if possible… First obtain a Junk Yard Instrument Cluster Harness Plug with a Goodly Length of the OEM Harness Wires still attached:

…AND REMEMBER… The PIN Orientation of the 24 Wire Instrument Cluster PLUG is LEFT to RIGHT …if the Harness Wires get DIRECTLY attached to IT …as opposed to attaching Individual Pin-Wire Connectors DIRECTLY to the Instrument Cluster 24 PIN Connector on the Board…as seen in the attached Video and has a RIGHT to LEFT Orientation and therefore… they are BACKWARDS to one another when Viewed Face On, side by side!

Then… you can wire either arrangement into the inexpensive J-1850 OBD2 Female Port and AFTER you Repair the LEDs, Mosfets and Dials on these GM Clusters… plug in either arrangement and Power Test the Lights and Dials… right there on your Bench. Yeee Haaaa!

So now… If you have your very own “GYMKO” Tech 2… So much the better for being able to run the actual Diagnostic Checks and Powered Bench Tests as though the Re-Built Cluster(s) were still mounted into the Dash Boards. I would recommend Downloading and saving this Video to obtain accurate Screen Prints of this Dude’s Hand Drawn Wire Diagram of this Harness …before his competitors find some way of getting this Video Deleted.

The Important Thing To Remember is… If you will be using this Cluster Bench Test Harness with any Tech 2 Clone… you MUST Insert the Tech 2 12 VDC 1 AMP Power Supply Plug or Cigarette Lighter Power Cord Plug …into the Male OBD2 Tech 2 Adapter…and NOT into the Base of the Tech 2 …otherwise, the Cluster will NOT Power Up:

Okay… To save everyone some time on this and memorialize the actual harness connection layout...

I worked out all of these ‘Visual Clues” into how the GM 24 PIN Instrument Cluster communicates with the Female OBD2 Port Connector (J-1850) with the Caveat that if you will be using a USB Blue Tooth Adapter… You will need an External Power Supply producing 12 Volts DC @ 1.389 Amps to connect the Three Wire from the 24 PIN Cluster Connector B+ Connectors over to PIN 16 for the Positive 12 VDCand then arrange the A12 and B12 Pins from the IC Connector over to PIN 4 of the J-1850 for GROUNDThis is NOT necessary to do when using the “GYMKO” Tech 2 Scanner:

Positive (3) Wire Bundle 24 PIN Cluster Connections:

Positive Power 12 VDC Wires
A11, B9 & B11

To… The J-1850 OBD2 Female Connections:
PIN 16 B+

Ground (2) Wire Bundle 24 PIN Cluster Connections:
A12 & B12

To… The J-1850 OBD2 Female Connections:

Class 2 Data Connections 24 PIN Cluster Connection:

To… The J-1850 OBD2 Female Connections: