Circuit Description
The body control module (BCM) system check is a test in order to identify an electronic system malfunction. The BCM system check is the starting point for any BCM concern. Understanding and using the BCM system check table will reduce diagnostic time. This prevents the unnecessary replacement of parts.
Test Description
Step number(s) below refer to the same step number(s) in the BCM system check table.
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This step determines if the data link connector (DLC) can power up the scan tool.
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Since most the diagnostic procedures require a scan tool, the serial data must be available. Step 1 is a test in order to ensure you can establish communications with the BCM.
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This step inspects for any diagnostic trouble codes (DTCs) stored in the BCM. When the scan tool can read the DTCs, the serial data line is functioning properly.
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This step inspects for class 2 communications with other systems. When the scan tool can read data, the class 2 serial data line is functioning properly.
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This step inspects for the TBC fuses located in the underhood bussed electrical center (UBEC).
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This step determines if CKT 352 (for the AUTO headlamps) is shorted to ground and blowing the TBC fuse.
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This step determines if the UBEC is suppling voltage to the TBC fuse.
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This step determines if the BCM power CKT 1140 is open between the BCM and the TBC fuse.
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This step determines if the BCM ground CKT 1850 is open.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
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Important: After a repair is made that requires clearing DTCs from the BCM, the repair must be inspected. Inspect the repair by operating the vehicle within the limits shown in Conditions for Setting the DTC. Operating the vehicle using the limits shown in the Conditions for Setting the DTC will verify if the repair is made correctly. Important: Probing the electrical circuits without the use of connector test adapter kit J 35616 could cause damage to the electrical components and the connectors. The J 35616 is the only recommended method of probing connectors, terminals, and bussed electrical centers (BECs). The J 35616 contains an assortment of flexible connectors. Use the flexible connectors in order to probe the connectors, the terminals, and the BECs during the diagnosis. | ||||
1 |
Does the scan tool power up? | -- | Go to Scan Tool Does Not Communicate with Class 2 Data Line in Wiring Systems. | |
2 |
Does the scan tool communicate with the BCM? | -- | ||
3 |
Does the scan tool display any current DTCs? | -- | Go to the appropriate service category for the applicable symptom diagnosis. | |
4 | Attempt to establish communications with other class 2 systems (i.e. the VCM/PCM, the IPC). Does the scan tool communicate with other class 2 systems? | -- | ||
5 | Inspect the TBC fuse. Is the TBC fuse open? | -- | ||
6 |
Is the TBC fuse open? | -- | ||
7 |
Does the test lamp light on either side of the fuse? | -- | ||
8 |
Does the test lamp light? | -- | ||
9 | Connect a test lamp to B+ and backprobe, in order to prevent damage to terminals, both BCM ground CKT 1850 (BLK) cavities A1 and B1 of the brown BCM (C1) connector. Does the test lamp light for both ground circuits? | -- | Go to Scan Tool Does Not Communicate with Class 2 Data Line in Wiring Systems. | |
10 | Locate and repair the open in CKT 1850 (BLK) between the BCM and ground. Is the repair complete? | -- | -- | |
11 |
Is the repair complete? | -- | -- | |
12 | Replace the UBEC. Is the repair complete? | -- | -- | |
13 | Locate and repair the open in CKT 1140 (ORN) between the BCM and the UBEC. Is the repair complete? | -- | -- | |
14 |
Are all DTCs cleared? | -- | System OK | -- |
