Networked Input Messages And Default States

Module messaging has increased over time and is the standard for sending and receiving information required to operate the IPC. The majority of the inputs required to operate the IPC are received over the CAN.

NOTE: Whenever a network message is suspected as missing and confirmed by a missing message DTC (U-code), it is important to look for other symptoms that can also be present in the IPC and throughout the vehicle. Once a DTC sets in the IPC, it is helpful to review the complete message list to determine other modules that also rely on the same message and run the self-test for those modules. If the message is missing from other modules, the same or similar lost communication DTC can also be set in those modules. Confirmation of missing messages common to multiple modules can indicate the originating module is the source of the concern or the communication network may be faulted.

For a list of all the network messages, Refer to: Communications Network - System Operation and Component Description .

The IPC uses input messages from other modules to control the gauges, informational indicators, warning indicators and message center message displays over the communication networks. There are 4 communication networks used to transmit the data used by the IPC.

HEV - HS-CAN
HS-CAN
MS-CAN
I-CAN

For overview, Refer to: Communications Network - Overview . For system operation, Refer to: Communications Network - System Operation and Component Description .

The majority of messaged inputs to the IPC are received from the GWM and the BCM. The GWM acts entirely as a gateway, where messages are received through one network and converted to another network recognized by the IPC. The BCM acts as a gateway but is also the source of indication requests sent to the IPC.

Network messages can drop out or be missing for a variety of reasons, such as high network traffic on the bus. The IPC incorporates a defined strategy for handling missing network messages based on time. The required time for a network message to be missing differs between the various gauges, indicators and message center displays. The strategy is basically the same for all indication outputs (gauges, indicators or chimes), but differs in the length of time required for the network message to be missing. If a required network message is missing or invalid for less than the programmed length of time, the gauge, indicator or message center display that requires the network message remains at the last commanded state based upon the last network message received. If the messaged input is missing for longer than the programmed length of time, the IPC output (gauge, indicator etc.) reacts according to a pre-defined default action.

For example, if the stability-traction control indicator request network message is missing for less than 5 seconds, and the stability-traction control indicator (sliding car icon) was on, the indicator remains in the on state until the next network message is received. If the network message remains missing or invalid for more than 5 seconds, the IPC sets a U-code DTC and the IPC output becomes a default action for the indicator or gauge. The indicator may default on/off or the gauge may default to the rest position.

Each indicator or gauge utilizes a different default strategy depending on the nature of the indication. Refer to the diagnostic overview descriptions located before each pinpoint test for further description of the default action specific to each indicator or gauge. If the missing messaged input to the IPC returns at any time, the normal function of the gauge, indicator or message center display resumes.

It is very important to understand:

where the input originates.
all the information necessary in order for a feature to operate.
which module(s) receive(s) the input or command message.
which module controls the output of the feature.
whether the module that receives the input controls the output of the feature, or whether it outputs a message over the communication network to another module.