Interior Lighting System: Overview Ford Explorer IV

The interior lighting system consists of the following components

1. Smart junction box (SJB)
2. Dimmer control switch
3. Interior/map lamps
4. Cargo lamp
5. Glove compartment lamp
6. Vanity mirror lamps
7. Door ajar switches
8. Puddle lamps

The interior lighting system consists of 2 subsystems

1. Courtesy lamps
2. Demand lamps

The courtesy lamps are controlled by the SJB. The courtesy lamp subsystem consists of the interior dome lamps, the puddle lamps and the overhead console lamps (if equipped). The SJB supplies voltage to the courtesy lamps when the SJB receives the required input.

The demand lamps are controlled by the SJB. The demand lamps subsystem consists of the glove compartment lamp, all map/reading lamps, and the left and right vanity mirror lamps.

The SJB supplies power to the interior lighting system. The SJB will set DTCs if certain circuit failures exist with the interior lighting system.

Special Tools Illustration Tool Name Tool Number 73III Automotive Meter 105-R0057 or equivalent Vehicle Communications Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool Flex Probe Kit 105-R025C or equivalent

Scheme 1

Scheme 2

Principles of Operation

The smart junction box (SJB) supplies voltage to the interior lighting system. The interior lighting system illuminates the courtesy lamps to enhance visibility of the interior while a vehicle door is open or ajar, and the vehicle speed is less than 15 km/h (9 mph). The SJB controls all interior lighting functions and timing by monitoring inputs from the door ajar switches, liftgate ajar switch, liftgate glass ajar switch, dimmer switch, and vehicle speed.

Normal Operation

Power is supplied to the courtesy lamps through the smart junction box (SJB) fuse 23 (15A), which supplies voltage to the courtesy lamps/demand lamps solid-state relay in the SJB. When any door, liftgate or liftgate glass is opened, the ajar switch opens, signaling the SJB. The SJB monitors the ajar circuits, and based on the ajar status, the SJB will energize the solid-state relay supplying voltage to the courtesy lamps on circuit CLN03 (YE/GY). Ground for the courtesy lamps is supplied through either circuit GD133 (BK) or circuit GD149 (BK/GY).

DTC B1374 - sets when the SJB detects a short to ground on the illuminated entry relay circuit.

Possible Causes

1. Fuse
2. Circuit CLN01 (GN/VT) short to ground
3. Circuit CLN03 (YE/GY) open or short to ground
4. Circuit CLN15 (GY/YE) short to ground
5. SJB

Circuit CLN03 (YE/GY) provides voltage to each courtesy lamp when activated. The courtesy lamps are grounded through circuits GD133 (BK) and GD149 (BK/GY).

Possible Causes

1. Circuit CLN03 (YE/GY) open
2. Circuit GD133 (BK) open
3. Circuit GD149 (BK/GY) open
4. Interior lamp

When any door, the liftgate or the liftgate glass is opened, the ajar switch opens the circuit to the smart junction box (SJB). The SJB monitors the ajar circuits, and based on the ajar status, the SJB will supply voltage to the courtesy lamps on circuit CLN03 (YE/GY).

DTC B1319 - sets when the SJB detects a switch/circuit failure on the LF door ajar circuit.

DTC B1327 - sets when the SJB detects a switch/circuit failure on the RF door ajar circuit.

DTC B1335 - sets when the SJB detects a switch/circuit failure on the RR door ajar circuit.

DTC B1571 - sets when the SJB detects a switch/circuit failure on the LR door ajar circuit.

DTC B1895 - sets when the SJB detects a output circuit failure on the LF, RF door ajar circuit.

DTC B1896 - sets when the SJB detects a short to voltage on the LF, RF, LR, RR door ajar circuit.

DTC B2077 - sets when the SJB detects a switch/circuit failure on the liftgate door ajar circuit.

Possible Causes

1. Circuit CLN03 (YE/GY) short to voltage
2. Circuit CLN28 (GN/BU) short to ground
3. Circuit CPL26 (GN/VT) open
4. Circuit CPL31 (GN/BK) open
5. Circuit CPL36 (GN) open
6. Circuit CPL39 (YE) open
7. Circuit CPL44 (YE/OG) open
8. Circuit CPL58 (GY/OG) open
9. Circuit GD143 (BK/VT or BK/OG) open
10. Dimmer control switch
11. Ajar switch
12. SJB

When any door, the liftgate or the liftgate glass is opened, the ajar switch opens the circuit to the smart junction box (SJB). The SJB monitors the ajar circuits, and based on the ajar status, the SJB will supply voltage to the courtesy lamps on circuit CLN03 (YE/GY).

Possible Causes

1. Circuit CPL26 (GN/VT) short to ground
2. Circuit CPL31 (GN/BK) short to ground
3. Circuit CPL36 (GN) short to ground
4. Circuit CPL39 (YE) short to ground
5. Circuit CPL44 (YE/OG) short to ground
6. Circuit CPL58 (GY/OG) short to ground
7. Ajar switch
8. SJB

The smart junction box (SJB) supplies voltage to the demand lamps on circuit CLN01 (GN/VT). The demand lamps are grounded through circuit GD133 (BK) or circuit GD149 (BK/GY).

DTC B1316 - sets when the SJB detects a short to ground on the battery saver relay coil circuit.

Possible Causes

1. Fuse
2. Circuit CLN01 (GN/VT) open or short to ground
3. SJB

The smart junction box (SJB) supplies voltage to the demand lamps on circuit CLN01 (GN/VT). The demand lamps are grounded through circuit GD133 (BK) or circuit GD149 (BK/GY).

Possible Causes

1. Circuit CLN01 (GN/VT) open
2. Circuit GD133 (BK) open
3. Circuit GD149 (BK/GY) open
4. Interior lamp

The illuminated entry provides interior lighting whenever the smart junction box (SJB) receives a doors unlock request from the RKE transmitter. The SJB provides voltage on circuit CLN03 (YE/GY) for the courtesy lamps.

Possible Causes

1. RKE system
2. SJB

The smart junction box (SJB) provides voltage to the glove compartment lamp on circuit CLN15 (GY/YE). The glove compartment lamp is grounded through circuit GD138 (BK/WH).

Possible Causes

1. Circuit CLN15 (GY/YE) open
2. Circuit GD138 (BK/WH) open
3. Glove compartment lamp
4. SJB

The smart junction box (SJB) provides a battery saver function. The battery saver function provides automatic shutoff of the interior lamps (courtesy lamps, demand lamps, and glove compartment lamp) after a predetermined time has elapsed in order to save battery power.

Possible Causes

1. Circuit CLN01 (GN/VT) short to voltage
2. Circuit CLN03 (YE/GY) short to voltage
3. SJB

The smart junction box (SJB) provides voltage to the puddle lamps through circuit CLN25 (VT). The puddle lamps have separate ground circuits. The LH exterior mirror is grounded through circuit GD133 (BK), and the RH exterior mirror is grounded through circuit GD151 (BK/GN).

DTC B2089 - sets when the SJB detects a puddle lamp fault.

Possible Causes

1. Circuit CLN25 (VT) open
2. Circuit GD133 (BK) open
3. Circuit GD151 (BK/GN) open
4. Exterior mirror
5. SJB

The smart junction box (SJB) monitors the dimmer control switch status on circuit CLN28 (GN/BU) to determine if the courtesy lamps are requested. Based on the dimmer control switch status, the SJB supplies voltage to the courtesy lamps through circuit CLN03 (YE/GY).

DTC B1687 - sets when the SJB detects a short to voltage on the dome defeat input circuit.

DTC B1688 - sets when the SJB detects a short to ground on the dome defeat input circuit.

DTC B2121 - sets when the SJB detects a short to voltage on the illumination switch circuit.

DTC B2132 - sets when the SJB detects a short to ground on the dimmer switch circuit.

Possible Causes

1. Circuit CLN28 (GN/BU) open
2. Dimmer control switch
3. SJB

The smart junction box (SJB) provides voltage to the puddle lamps and the cargo lamp through circuit CLN25 (VT). The puddle lamps and the cargo lamp have separate ground circuits. The LH exterior mirror is grounded through circuit GD133 (BK), and the RH exterior mirror is grounded through circuit GD151 (BK/GN). The cargo lamp is grounded through circuit GD133 (BK).

DTC B2089 - sets when the SJB detects a puddle lamp fault.

Possible Causes

1. Circuit CLN25 (VT) open
2. Circuit GD133 (BK) open
3. Circuit GD151 (BK/GN) open
4. Exterior mirror
5. SJB