B2618

CIRCUIT DESCRIPTION
Battery positive voltage is supplied through the CTSY LP 15 A fuse in the engine wiring harness junction block, to both the normally open inadvertent power relay switch contacts, and to the inadvertent power relay coil. The body control module (BCM) activates the inadvertent power relay providing battery positive voltage to all interior courtesy lamp circuits including the courtesy lamp relay coil. When any doer is opened or a courtesy lamp request input is received by the BCM, the BCM will energize the courtesy lamp relay. The normally open courtesy lamp relay switch closes, grounding the courtesy lamp circuit to G203. So all the interior courtesy lamps nave battery positive voltage and ground, and illuminate.

The inadvertent power relay also provides battery positive voltage to each vanity mirror lamp, the instrument panel compartment (glove box) lamp, underhood lamp and the cargo lamp. When either the compartment is opened or its switch is closed to provide a ground circuit, the lamps have power and ground and illuminate.

hen the driver turns ON the interior lamp switch, or the dome lamp defeat switch, the BCM will override any other input, either turning the courtesy lamps ON or preventing them from illuminating.

If the driver inadvertently leaves the interior, reading or compartment lamp ON the BCM will de-energize the inadvertent power relay, preventing a dead battery.

CONDITIONS FOR RUNNING THE DTC
^ The system voltage must be between 9.0 and 16.0 volts.
^ The ignition switch in the OFF position.
^ Unlock doors from the remote control door lock key fob, or open any door, or turn ON the dome lamp from the switch (thumbwheel).
^ The above conditions must be met for more than 0.5 seconds.

CONDITIONS FOR SETTING THE DTC
To set B2618, the following conditions must be present:
^ Courtesy lamps ON.
^ The courtesy lamp relay coil control circuit is open or shorted to ground.
^ The above conditions must be met for 0.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The courtesy lights will not function.

CONDITIONS FOR CLEARING THE DTC
^ This DTC will clear after a fault free ignition cycle.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ A clear codes message is sent by the scan tool.

DIAGNOSTIC AIDS

IMPORTANT: Use the appropriate probe from the J 35616-A connector test adapter kit for any probing of the electrical components in this table, in order to avoid damage to the terminals.

^ The scan tool must display DTC B2618 as a current code before performing these diagnostics.
^ Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-2:

Steps 3-13:

The number(s) below refer to the step number(s) on the diagnostic table.
2. Listen for an audible click when the courtesy lamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the courtesy lamp relay. The CTSY fuse supplies power to the coil side of the courtesy lamp relay.
4. Verifies that the body control module is providing ground to the courtesy lamp relay.
5. Tests if ground is constantly being applied to the courtesy lamp relay.
12. After replacement of the BCM you must calibrate the new module for proper operation.