Editor's Note: This article was orginally published Jan. 3, 2012. Some of the information may no longer be relevant, so please use it at your discretion.
This month, we are going to cover a work-around for the need of two expensive specialty tools required to program model year 2000 and later Cadillac Deville, Seville and Eldorado models as well as 1997 or later Corvettes. These tools are needed on these various models up until each changed to employing CAN communication at the DLC.
The Cadillac tool is the J-45211. It is supposed to be used to isolate the PCM from other networked computers' activity that can interrupt the communication between the Tech 2 or other programming tool and the PCM. The Corvette tool is the J-42236-A serial data link tester, which is supposed to be attached to vehicle wire harness splice packs in place of the shorting bars. The tester isolates the PCM from the rest of the network for the same reason as the Cadillac tool.
Neither of these tools is mentioned in the usual service manual how-to areas. You typically find out about these tools only when the message contained within programming software pops up and alerts you to the need for them. Knowing that the intent of these specialty tools is to isolate the PCM from the rest of the vehicle network, we can build our own inexpensive isolation tool consisting of a long piece of wire and two appropriate wire terminals.
We are going to temporarily remove the existing vehicle harness communication wires from the PCM connector. We also are going to remove the vehicle to scan tool communication wire from the DLC connector cavity. We then will install an overlay programming wire into the DLC and PCM connectors where the other terminals were removed.
To build our programming harness, we will need the appropriate wire terminal ends that match both PCMs for the Cadillacs and the Corvette. They are the same. In addition, we need the terminal for the DLC. The PCM connector terminals are the Delphi Micro-Pack No. 12084913; the DLC connector terminals are the Delphi Metri-pack 280 No. 15317575. Type these terminal name and part numbers into your Internet search engine and you will come up with a number of providers from which to purchase them. Take the acquired terminals and connect them with a piece of wire about 20 feet long. We will now describe how to install the programming harness.
The upper portion of Figure 1 shows the removal process of the purple Class 2 scan tool communication wire from Terminal 2 of the DLC. Simply use a toothpick or other suitable tool to push down on the DLC connector wire terminal lock tab while pulling the wire out of the back of the connector cavity. Then push your programming harness in the back of the DLC until you hear or feel the lock tank engage the terminal.
After this wire is removed from the PCM connector, we will install our programming harness in its place. This is typically PCM connector Terminal 59. Consult your service information system wiring diagrams to choose the correct terminals on your subject vehicle.
To remove the PCM connector terminals unbolt the PCM connector from the PCM. Then use a small screwdriver to remove the blue Terminal Position Assurance (TPA) cover by depressing the white TPA lock tabs on the sides of the connector cavity. Next, use a suitable tool to lift up the individual PCM terminal lock tang away from the terminal. Pull the PCM harness out the back of the connector. Install your programming harness terminal in the PCM-DLC terminal socket. Being that both the removed Class 2 communication wires are purple, I like to use a colored marker to mark one purple wire and its corresponding connector socket for error free re-assembly.
Now that your PCM and DLC are wired separately from the rest of the vehicle network, simply use your chosen programming tool in the normal fashion to complete the programming process. Reinstall all harness connections after the programming event to their original state.
Jim Garrido of "Have Scanner Will Travel" is an on-site mobile diagnostics expert for hire. Jim services independent repair shops in central North Carolina. He also teaches diagnostic classes regionally for CARQUEST Technical Institute.
