FILTER 3066338 - Caterpillar

Introduction
With the installation of the Product Link 121 and Product Link 321 (PL121 and PL321), there are issues involving miswiring.Problem
On a regular basis, Caterpillar Electronics Product Support receives service requests through the Dealer Solution Network (DSN) with the issue of Caterpillar Electronic Technician (ET) Error "142" (The interface hardware is not responding). CAT ET Error "142" is almost always related to the miswiring of the PL121SR radio modem and the PL321 radio modem.Refer to Illustration 1 and Illustration 2. In both illustrations you will notice a circle around the point where the two harnesses connect to each other. This is where the problem exists. The 12-pin 155-2252 Connector Plug As (on the 256-6803 Radio Harness As ) that plugs into the PL121 radio is identical to the 155-2252 Connector Plug As that is used on the Legacy harness or Product Link (PL) ready conversion harness. What we are finding is that the technician is plugging the Legacy harness or the PL ready conversion harness directly into the radio without the 256-6803 Radio Harness As .This miswiring will correctly supply power, ground, key switch, and R-Terminal to the radio and will give the false impression that everything is wired correctly. However, the communication lines for the serial service connector are not routed to the proper pins. This is what causes the CAT ET Error "142".Solution
The PL121SR radio modem requires a minimum of TWO harnesses for proper operation. Refer to Illustration 1 and Illustration 2. Illustration 1 depicts a legacy (non Product Link (PL) ready machine) and Illustration 2 depicts a PL ready machine. You will notice a common harness between the two illustrations. That common harness is the harness that is identified as the 256-6803 Radio Harness As .To clarify, the 256-6803 Radio Harness As is the only harness that should plug into the PL121 radio modem.
Illustration 1 g01226630
Legacy Machine
Illustration 2 g01226639
Product Link Ready Machine