Circuit Description
DTC B2648 (both current and history) indicates a short to battery in the ambient light sensor signal circuit.
Conditions for Setting the DTC
All of the following conditions must be met:
| • | The automatic lighting control (ALC) option is enabled. |
| • | Ignition 1 is active. |
| • | The ambient light sensor analog input is shorted to voltage for 5 seconds. |
Action Taken When the DTC Sets
| • | Stores DTC B2648 in the body control module (BCM) memory. |
| • | The SERVICE VEHICLE SOON indicator illuminates. |
Conditions for Clearing the DTC
| • | The body control module (BCM) goes to sleep and reinitializes with the fault cleared. |
| • | All BCM history codes clear after 100 ignition cycles (from OFF to ON) with no current codes active. |
| • | Clear history and current DTCs using a Scan Tool scan tool. |
Diagnostic Aids
If the DTC is a history DTC the problem may be intermittent. Perform the above tests while wiggling the wiring and connectors. This may often cause the malfunction to appear.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
|
Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open. | ||||
1 | Was the BCM System Check performed? | -- | Go to Step 2 | |
Is the measured resistance equal to the specified value? | 0V | Go to Step 4 | Go to Step 3 | |
3 | Repair the short to B+ in CKT 1138 between the ambient light sensor connector terminal B and the BCM connector C2 terminal A3. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 5 | -- |
4 | Replace the ambient light sensor. Is the repair complete? | -- | Go to Step 5 | -- |
5 |
Did DTC B2648 clear from memory? | -- | Go to Step 7 | Go to Step 6 |
6 | Replace the BCM. Refer to the following procedures: Is the repair complete? | -- | Go to Step 7 | -- |
7 | Clear the DTCs from memory. Are the DTCs cleared from memory? | -- | -- | |
