Diagnostic Information

Use the Diagnostic Trouble Code (DTC) tables in this section in order to locate a faulty circuit or a component through the process of elimination. The BCM performs a continual self-diagnosis on certain control functions. A DTC sets when a malfunction is detected by the BCM. The BCM will not turn the SERVICE ENGINE SOON malfunction indicator lamp (MIL) to the ON position.

Class 2 Serial Data Communication

The Class 2 network continually monitors various subsystems (i.e. ATC, BCM, HVAC, IPC, PCM, and VCM) and operating conditions for possible system malfunctions. Compare the system conditions against standard operating limits in order to detect certain circuit and component malfunctions. A 5-digit alphanumeric diagnostic trouble code (DTC) is stored in the computer memory. When a malfunction is detected by this self-diagnostic system, the DTC(s) may later be retrieved by the service technician using a scan tool. The scan tool may aid the technician in repairing various subsystems.

Data Link Connector (DLC)

The 16-pin DLC is wired to the body control module. The 16-pin DLC is located under the dash panel on the left side. The DLC connector has terminals that are used in order to connect to a scan tool. The following list shows some common uses of the scan tool:

Scan Tool Diagnosis

Use the scan tool in order to monitor the communications between the BCM and the PCM/VCM. The scan tool also displays Passlock™ data. The Passlock™ data list display is located under the PASSLOCK selection. This list shows the status of the hardwired connections from the Passlock™ sensor to the BCM. These scan tool values may be very useful in diagnosing the Passlock™ system.

The Passlock™ system is designed in order to deter theft, even if various parts are changed. The following components may not be changed without the possibility of entering into no-start condition:

If any of these parts are replaced, refer to the Learn Procedure in Body Control Module (BCM) Programming/RPO Configuration . The BCM and the PCM/VCM require the full 10 minutes in order to complete a lockout cycle. The ignition key MUST remain in the RUN position until the telltale turns to the OFF position. If the ignition key is turned from the RUN position before the telltale turns to the OFF position, you will have to repeat the lockout cycle. The Passlock™ system requires 3 consecutive lockout cycles in order to complete the 30 minute learn procedure for a changed component. Refer to Theft Deterrent for more information on the Passlock™ system.

Scan Tool Information Modes

On the scan tool, four modes are available in the body control module selection. Select the following items:

1. Body control module
2. Data display
3. Data list

The following list appears on the scan tool:

The scan tool allows for the for the display of Class 2 values, or the state of components commanded by the various systems (i.e. ATC, BCM, HVAC, IPC, PCM and VCM). The tests available are dependent upon the system selected, but may include the following modes:

Data (analog inputs): This test displays analog values as seen by the system.

Inputs (digital inputs): This test displays digital values as seen by the system and provides an indication of whether the input has cycled.

Outputs (digital outputs): This test allows for digital outputs controlled by the BCM system in order to be turned OFF/ON.

Special functions (analog outputs): This test allows for analog outputs of the BCM system to be set at a desired value.

Clear diagnostic trouble codes (DTCs): This test will erase all DTCs stored for the system currently selected. If the malfunction is still present, the DTC may immediately reset.

Security data (content theft): This test contains information system applicable to the content theft system.

The Diagnostic Executive

The diagnostic executive is a unique segment of software that is designed in order to perform the following functions:

The following list shows the main responsibilities of the diagnostic executive:

A diagnostic test is a series of steps that has a beginning and an end. The result of a diagnostic test is pass or fail, which is reported to the diagnostic executive. When a diagnostic test reports a pass result, the diagnostic executive records the following data:

The fault identified by the diagnostic test is not currently active.

When a diagnostic test reports a fail result, the diagnostic executive records the following data:

Diagnostic Trouble Code (DTC) Diagnosis

This section uses the following items in order to direct you in performing specific tests in order to locate and repair the problem:

The diagnostic table is a step by step procedure used in order to determine the circuit or the component that is the source of the problem. The following items are located above the diagnostic table:

When the diagnostic trouble codes (DTCs) are set, the BCM detects a malfunction in a particular circuit or other system. Other system malfunctions are generally (but not exclusively) reported to the BCM via Class 2 data message. The BCM is programmed with routines for internal checks that the BCM follows only under prescribed conditions (called test conditions). When these conditions exist, the BCM inspects certain circuits or systems for a malfunction. These inspections are called failure conditions or conditions for setting the DTC. When these conditions are true, a DTC is set. The BCM turns the SECURITY malfunction indicator lamp (MIL) to the ON position for the Passlock™ system related malfunctions. Refer to the applicable DTC table for procedures and details.