HARNESS AS 8E6402 - Caterpillar

Note: If you are experiencing problems with communications between the Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM), refer to Troubleshooting, "Electronic Service Tool Will Not Communicate with ECM" before you use this procedure.This procedure checks the Cat Data Link. The Electronic Control Modules communicate with each other and with Cat ET via the Cat Data Link. Each engine ECM has diagnostic codes for the data link:Tractor Engine
562-09 Unable to Communicate with Cat Monitoring System
562-12 Wrong Response from Cat Monitoring System
1273-09 Unable to Communicate with Chassis Control Module
1421-09 Unable to Communicate with Rear Engine ECMScraper Engine
296-09 Unable to Communicate with Transmission ECM
562-09 Unable to Communicate with Cat Monitoring System
562-12 Wrong Response from Cat Monitoring System
1273-09 Unable to Communicate with Chassis Control Module
1422-09 Unable to Communicate with Front Engine ECM
1422-12 Front Engine Control Module MalfunctionThe active codes can help identify the problem. For example, if both engines have active codes for the Caterpillar Monitoring System (CMS), the CMS or the wiring to the CMS is the most likely cause of the codes.
Illustration 1 g01143755
Schematic diagram of the Cat Data Link
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the connectors for each of the modules. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Illustration 2 g01104274
Engine ECM P1 terminals that are associated with the Cat Data Link
(P1-8) Cat Data Link +
(P1-9) Cat Data Link −
Illustration 3 g01142121
Transmission ECM P1 terminals that are associated with the Cat Data Link
(P1-7) Cat Data Link −
(P1-8) Cat Data Link +
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the Cat Data Link.
Check the torque of the allen head screws for the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and the connectors appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or the wiring are not OK.Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the original problem is resolved.STOPTest Step 2. Check for a Short Circuit
Verify that the keyswitch is in the OFF position.
Disconnect Cat ET from the service tool connector.
Measure the resistance between the points that are listed in Table 1. You may perform the measurements at either service tool connector. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
Table 1
Service Tool Connector
Resistance Measurements for the Cat Data Link
Terminal Terminal
D (Cat Data Link +) E (Cat Data Link -)
A (+Battery)
B (-Battery)
E (Cat Data Link -) A (+Battery)
B (-Battery) Expected Result:Each check of