DTC U1300: Class 2 Communications Circuit Shorted To Ground (Century, Intrigue & Regal)

1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Install scan tool. Using scan tool, attempt to establish communication with other modules connected to serial data line. If communication can be established, go to step 9)  . If communication cannot be established, go to next step.
3. Turn ignition off. Disconnect instrument cluster, heater-A/C control, Body Control Module (BCM), and Powertrain Control Module (PCM). Disconnect 24-pin EBCM/EBTCM connector C1 and 8-pin EBCM/EBTCM connector C2. See EBCM/EBTCM LOCATION  under REMOVAL & INSTALLATION. Using DVOM, measure resistance between terminals No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 11)  .
4. Turn ignition off. Reconnect instrument cluster. Turn ignition on, with engine off. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 12)  .
5. Turn ignition off. Reconnect heater-A/C control. Turn ignition on, with engine off. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 13)  .
6. Turn ignition off. Reconnect BCM. Turn ignition on, with engine off. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 14)  .
7. Turn ignition off. Reconnect PCM. Turn ignition on, with engine off. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 15)  .
8. Turn ignition off. Reconnect EBCM/EBTCM connectors C1 and C2. Turn ignition on, with engine off. Using DVOM, measure resistance between terminal No. 2 (Purple wire) of DLC and ground. If resistance is infinite, go to step 17)  . If resistance is not infinite, go to step 16)  .
9. Turn ignition off. Disconnect 24-pin EBCM/EBTCM connector C1. Check EBCM/EBTCM connector C1 for poor terminal contact, corrosion or damage. If connector is faulty, go to next step. If connector is okay, go to step 17)  .
10. Replace all faulty terminals or connectors.
11. Repair short to ground in serial data line. See appropriate diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.
12. Repair short to ground in instrument cluster. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
13. Repair short to ground in heater-A/C control. See appropriate AIR CONDITIONING & HEATING SERVICE & REPAIR article.
14. Repair short to ground in BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
15. Repair PCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
16. Replace EBCM/EBTCM. See ELECTRONIC BRAKE CONTROL MODULE/ ELECTRONIC BRAKE & TRACTION CONTROL MODULE (EBCM/EBTCM)  under REMOVAL & INSTALLATION.
17. Malfunction is not currently present. Before performing diagnostic testing for DTC U1300, perform PCM on-board diagnostic system check to eliminate possible faulty PCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside insulation. Frequency of malfunction can be determined by using enhanced diagnostic function of scan tool. Check for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wiring connections, or damaged wiring harness.