Running Board Lamps Malfunction

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information

Circuit	Circuit Function	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performan
4748	Control	B1B0C 11	1	1	—
4749	Control	B1B0D 11	1	1	—
1650	Ground	—	1	—	—
1. Running Board Lamp Malfunction

Scan Tool Functions K4 Running Board Control Module – Control Functions

Control Function	Description
Assist Step Courtesy Lamp	This control function will control the running board lamps ON/OFF

Circuit/System Description When equipped (B3L), the running board assist step lamps become illuminated anytime lock/unlock is pressed on the keyless entry transmitter during low ambient light conditions as part of the approach lighting system. The K9 Body Control Module responds to the lock/unlock request during low ambient light conditions by sending a serial data message to the K4 Running Board Control Module to command the running board assist step lamps on. The running board control module responds by applying voltage to the running board assist step lamp control circuits illuminating the running board assist step lamp LEDs. Reference Information Schematic Reference Step/Running Board Schematics Connector End View Reference Master Electrical Component List Description and Operation Exterior Lighting Systems Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

1. Ignition on/vehicle in service mode
2. Verify both running board assist step lamps turn on and off when commanding the Assist Step Courtesy Lamp ON and OFF with a scan tool. ⇒ If the running board assist step lamps do not turn on and off Refer to Circuit/System Testing ⇓ If the running board assist step lamps turn on and off
3. A fault is not currently present and may be an intermittent condition. Circuit/System Testing
4. Ignition/vehicle OFF, disconnect the appropriate component: E8ZL Assist Step Lamp – Left E8ZR Assist Step Lamp – Right
5. Verify a test lamp illuminates between ground circuit terminal 1 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on the ground circuit or ground connection. ⇓ If the test lamp illuminates
6. Connect a test lamp between control circuit terminal 2 and ground, ignition on/vehicle in service mode.
7. Verify the test lamp turns ON and OFF when commanding the Assist Step Courtesy Lamp ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test the appropriate circuit for a short to ground: E8ZL Assist Step Lamp – Left = Circuit 4748 E8ZR Assist Step Lamp – Right = Circuit 4749 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test the appropriate circuit for an open/high resistance: E8ZL Assist Step Lamp – Left = Circuit 4748 E8ZR Assist Step Lamp – Right = Circuit 4749 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Replace the K4 Running Board Control Module. ⇒ If the test lamp is always ON 4.1. Test the appropriate circuit for a short to voltage: E8ZL Assist Step Lamp – Left = Circuit 4748 E8ZR Assist Step Lamp – Right = Circuit 4749 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 4.2. Replace the K4 Running Board Control Module. ⇓ If the test lamp turns ON and OFF
8. Replace the E8Z Assist Step Lamp. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup