Loss Of High Speed LAN Communications - keywords module no U0073 U2100 U0100 U0101 U0102 U0109 U0121 U0132 U0140

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

You may experience a vehicle that has a loss of high speed LAN communications. Below are some possible symptoms of a loss of high speed LAN communications

1. One or Multiple U codes in one or more modules, such as DTC: DTC U0073, U2100, U0100, U0101 U0102, U0109, U0121, U0132, U0140 or U0132
2. IPC gauges drop or fluctuate and multiple service messages displayed on the DIC (Drivers Information Center) or SIR, SES, Traction, ABS, or Red Brake indicator on.
3. Door locks cycle while driving
4. No Crank
5. Vehicle shifts hard or defaults.

If you experience one or more of the symptoms above, review the following area's for a possible concern.

1. Inspect the EBCM connector for loose terminals or low pin retention at pins: 8, 9, 23, and 24. These pins are for circuits 2500 and 2501 for high speed LAN communications with the EBCM, TCM, and ECM. Use the proper test tool when checking pin tension. The proper test tool for this EBCM is J-35616-64B which should be supplied in the GM terminal test kit. If the pins are loose or damaged, replaced all 4 pins with new terminals. (part number #7116-3703-02 that is located in tray 14 of the GM terminal kit.)
2. Inspect the Transmission pass-through connector for loose or low pin retention at pins: 10, 11, 13, and 14. Also make sure these pins are fully seated into the connector. See photo below for location and a photo that shows a terminal that was not full seated into the transmission connector. Repair as needed.





3. Check for a pinched/cut wiring harness where the transmission harness is attached to the transmission. The metal attachment clip may be cutting into the harness and shorting the high speed LAN circuit to ground. (Location and style of clip is shown in Photo Below) Repair as needed.





4. Check for chaffed or shorted wiring by the park brake bracket assembly to the left IP Junction Block
5. Inspect underneath the (UBEC) Under Hood Buss Electrical Center for pinch or chaffed wires on the UBEC support bracket.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.