Loss of Communication while Viewing HMI Data List

While performing service procedures involving the Human Machine Interface (HMI) module, viewing the HMI data parameters using GDS2 may cause a temporary loss of communication with the scan tool. This condition may be found on 2016 ELR; 2016-2017 ATS, CTS, XTS; 2016-2018 Encore, Envision, LaCrosse, Regal, CT6, Escalade, Camaro, Colorado, Corvette, Impala, Malibu, Silverado, Suburban, Tahoe, Canyon, Sierra; 2017-2018 XT5, Acadia; and 2018 Equinox models equipped with RPOs IO5, IO6, RAO, or UY4.


On some vehicles, viewing the HMI data parameters (Fig. 9) for as little as 5–60 seconds using GDS2 may induce a temporary loss of HMI communication with the scan tool. This condition may occur on a vehicle that has no concerns as well as a vehicle that has an unrelated customer concern. If a loss of HMI communication occurs with no other conditions, do not replace the HMI module.


Fig. 9


Power Cycle the HMI Module


Communication can sometimes be re-established with GDS2 by simply clicking OK when the “No HMI Communication” screen is displayed. In some other cases, it may be necessary to remove the HMI fuse for a few seconds and then reinstall the fuse to re-establish HMI communication. If there are not any related DTCs set or other concerns with the HMI, the HMI data parameters should be temporarily viewable again (for only one minute or less) after reinstalling the HMI fuse, before the cycle starts again.


If the loss of HMI communication with GDS2 occurs and TIS2Web is used to program the HMI module without first restoring communication with the HMI module by power cycling it (cycling the fuse for a few seconds or cancelling Retained Accessory Power), an E-4491 SPS error code may appear. However, the HMI module should not be damaged and it should be possible to continue with programming by power cycling the HMI module and then immediately entering TIS2Web.


The loss of HMI communication while viewing the HMI data parameters using GDS2 is due to a software issue that causes the HMI to the prematurely leave the diagnostic/service mode and return to normal operation.


Do not replace the HMI module or any other parts if this condition is found. GM Engineering is currently evaluating this condition. In the meantime, power cycling the HMI fuse should restore communication unless another issue exists that requires further diagnosis and repair.


– Thanks to Ryan Dorland

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