Use a scan tool to display IPC data. This information assists in determining whether the IPC is operating properly and whether the IPC is sending or receiving the proper data to and from a particular system. The IPC uses data received from other systems in order to carry out some functions. Therefore, if the IPC receives the incorrect data from another system, the IPC may function improperly. Use the scan tool in order to review the data from the systems that interact with the IPC. An example of the use of the scan tool data display functions, using an oil pressure gauge system malfunction as an example might involve Powertrain Control Module (PCM) data display. If the oil pressure gauge does not display the proper oil pressure readings or a LOW OIL PRESSURE message is displayed. To diagnose this condition using a scan tool, select the PCMs data display function, then check if the PCM is receiving and interpreting the proper oil pressure data from the sensor. If the PCM is not reading the proper oil pressure the IPC is not the problem and the PCM must be further diagnosed. If the PCM is receiving and interpreting the proper oil pressure data, select the IPC data display function, then check if the IPC is able to receive the proper oil pressure data from the PCM. If the IPC oil pressure data is correct and the oil pressure gauge does not function properly, use the scan tool's output control function to command the oil pressure gauge to a fix command position. This is an example of how the scan tool and IPCs diagnostics can provide valuable information without any time spent on disassembly of the vehicle or probing of circuits. This example can be applied to an indicator malfunction or other warning messages displayed as well as other IPC malfunctions.

The scan tool's input display function can be helpful in determining if the IPC is receiving the correct input status. This can assist in determining if a system is "seeing" a system operate as intended. For example, the IPC requires the door ajar switch status from the Body Control Module (BCM) to display the DOOR AJAR message. If the DOOR AJAR message is always displayed, a starting point might be selecting the BCM door ajar input diagnostic function from the scan tool menu. The input status will be displayed as ACTIVE or INACTIVE. If, again using the door ajar switch input to the BCM as an example, if the BCM door ajar input display mode was entered with the door open the scan tool would display ACTIVE. If the door is then closed the scan tool display would change to show INACTIVE. If the input state display never changes when a system is operated, that system could be malfunctioning. If the display input is constantly ACTIVE never changing to INACTIVE, or INACTIVE never changing to ACTIVE, the input could be stuck . This could be caused by a short, open or malfunctioning switch, or in rare instances the BCM itself. Check if the IPC is receiving the correct input information from the Body Control Module (BCM). If the BCM is receiving the correct input information, then perform the same procedure using the IPC to determine if the IPC is actually able to receive this input information on the serial data line from the BCM. If the IPC recognizes the door is close, but still displays the DOOR AJAR message, the IPC requires additional diagnosis. This example can be applied to an indicator malfunction or other warning messages displayed as well as other IPC malfunctions.

A scan tool may be used to command IPC functions without the need for input information from other systems. This can be very helpful in determining if a certain portion of a circuit or component is in working order. Using a scan tool, select the IPC special functions from the scan tool menu. The status of the output being cycled will be shown on the scan tool's display screen. The telltales/indicator can be cycled to turn ON and OFF or gauges may be commanded to a specific position by using the scan tool output control function. Using the IPC output function and the oil pressure gauge as an example, commanding the oil pressure gauge to a specific position can indicate whether oil pressure gauge itself is operating correctly. It also can determine if the IPC internal circuitry is able to operate the oil pressure gauge. If, for example, the IPC unable to respond to the scan tool's request to command the oil pressure gauge to a specific position, then a malfunction may present in the gauge or the IPC itself. If the IPC is able to properly control the oil pressure gauge with the scan tool, but the oil pressure gauge still does not function properly, there is a good possibility that the problem lies with the Powertrain Control Module (PCM) not able to sent the IPC the correct oil pressure data. This example can be applied to an indicator malfunction or other warning messages displayed as well as other IPC malfunctions.