Diagnostics and testing of rear lights (Discovery 3)

Tail lights, parking lights, license plate lights

1. Ensure that the customer's complaint is justified.

2. Visually inspect for obvious electrical problems.

Mechanical factors

Electrical factors

Condition and installation of the rear light(s) Condition and installation of license plate lights Lamps and installation Lamp holders and installation Light switch and its installation Rain/light sensor status and installation

Fuses Battery junction box (BJB) - fusible link 15E BJB - fusible link 16E BJB - fusible link 11E BJB - fusible link 25E Central junction box (CJB) - fuse 2P CJB - fuse 42P CJB - fuse 18P CJB - fuse 67P CJB - fuse 62P Relay Tail/License Plate Light Relay Automatic Headlight Relay Wiring harness Loosening or corrosion of connector(s) Battery Junction Box (BJB) Central Junction Box (CJB) Rain/Light Sensor Control Module LIN electrical circuits (Local interconnect network) CAN electrical circuits (Control Area Network)

3. If an obvious cause for the problem you identified or the customer described is found, correct it before moving on to further actions. (if possible).

4. Use the approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the symptom chart or DTC index.

Since DTCs are stored in more than one module, a full vehicle data read is recommended.

Clear all DTCs after troubleshooting.

Table of signs of malfunction

Sign of malfunction	Possible reasons	Actions
Tail light(s)/license plate light(s) not working	Lamp failure The fuse(s) have blown Electrical circuit failure The light switch is faulty	Check the condition of the lamp and fuse (see visual inspection table). Check the electrical circuits of the taillights/license plate lights. Check the operation of the light switch. Refer to the electrical equipment manual. Check for DTC codes that indicate a malfunction in the electrical circuits of the rear lights/license plate lights.
Dim light from rear light(s)/license plate light(s)	Incorrect lamp power Malfunction electrical circuit The light switch is faulty	Check the condition and power of the lamp. Check the electrical circuits of the tail lights/license plate lights. Check the operation of the light switch. Refer to the electrical equipment manual.
Tail light(s)/license plate light(s) stays on	Electrical circuit failure The light switch is faulty	Check the electrical circuits of the taillights/license plate lights. Check the operation of the light switch. Refer to the electrical equipment manual. Check for DTC codes that indicate a malfunction in the electrical circuits of the rear lights/license plate lights.
The tail light(s)/license plate light(s) do not operate when the automatic headlight mode is selected.	The fuse(s) have blown The light switch is faulty Electrical circuit failure Rain/light sensor is faulty LIN electrical circuit failure	Check the fuse(s) (see visual inspection). Check the operation of the light switch. Check the automatic headlight circuit. Refer to the electrical manual. Check for DTCs indicating a malfunction of the rain/light sensor or LIN system.

DTC Index

NOTE: Generic scan tools cannot read the codes listed or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7-digit code to identify the fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

(Details can be found on the website LRman.ru)

DTC codes	Description	Possible reasons	Actions
B1A9801	LIN bus - electrical circuit No.1	LIN bus: short circuit to battery + or ground	Refer to the guided diagnostic program for this code on the approved diagnostic system. The LIN bus provides serial communication with the rain sensor, sunroof, optional seat memory modules, and DTC logging is controlled by the vehicle configuration file (CCF) (depending on the installation). Repair is only required when one or more devices are not installed and are not working properly. See the "Lost Connection" condition description at the beginning of this table.
B1A9881	LIN bus - electrical circuit No.1	Software error Power failure when transmitting rain/light sensor signal	Refer to the guided diagnostic program for this code on the approved diagnostic system. No repair is required unless there is a customer complaint about poor rain sensor, sunroof, or seat memory operation. The LIN bus provides serial communication with the optional rain sensor, sunroof, and seat memory modules, and DTC logging is controlled by the vehicle configuration file (CCF) (depending on the installation). Repair is only required when one or more devices are not installed and are not working properly. See the "Lost Connection" condition description at the beginning of this table.
B1A9883	LIN bus - electrical circuit No.1	LIN bus checksum error	Refer to the guided diagnostic program for this code on the approved diagnostic system. The LIN bus provides serial communication with the rain sensor, sunroof, optional seat memory modules, and DTC logging is controlled by the vehicle configuration file (CCF) (depending on the installation). Repair is only required when one or more devices are not installed and are not working properly. See the "Lost Connection" condition description at the beginning of this table.
B1B551C	Rain sensor module	The rain sensor supply voltage is not normal	Refer to the guided diagnostic routine for this code on the approved diagnostic system. Refer to the electrical guides and check for power to the sensor module from the CJB, repair as necessary. If power is present, no action required, clear/ignore DTC.
B1B5546	Rain sensor module	Rain sensor parameter/calibration memory failure: Initialization error - unable to perform optical calibration	Refer to the guided diagnostic program for this code on the approved diagnostic system. Check the windshield for cleanliness in the sensor installation area. Check that the sensor is installed correctly on the optical element and that the optical element fits tightly to the windshield. Clear the DTC and retest. If the DTC reappears, replace the rain/light sensor.
B1B5549	Rain sensor module	Internal electronic malfunction	Check the rain/light sensor module and electrical circuit. Refer to the electrical manual. If the module is suspected, refer to the warranty policy and procedures manual.
B1B5587	Rain sensor module	No message	Refer to the guided diagnostic program for this code on the approved diagnostic system. The rain sensor is not installed on all models. (custom installation). Registration of the failure is prohibited by the CCF file, but if the CCF file is incorrectly configured, a DTC may be registered by mistake. Repair is required only for vehicles with a sunroof. If necessary, refer to the description of the "Lost Communication" condition at the beginning of the "Communication Systems Module" section.
B1B5591	Rain sensor module	Rain sensor module - the measured temperature is outside the normal operating range.	No action required, clear/ignore DTC.
B1C6012	Parking light relay output circuit	Parking light relay output circuit: short circuit to battery + Brake/tail light bulbs not in compliance with standard Brake/tail light bulbs are faulty	A bulb failure may also cause DTC B1B0187 to be set in the data network module and DTC C1A5564 to be set in the parking brake module. A failure in this circuit that causes DTC B1C6012 to be set may also cause automatic transmission shifting problems. Check for correct tail/brake lamp bulb type, improper installation, or faults including shorted filaments. Refer to the electrical guides and check the tail lamp relay output circuit. Replace/repair as necessary.
B1C6014	Parking light relay output circuit	Tail/License Plate Light Relay Output Circuit Short to Ground Tail/License Plate Relay Output Circuit High Resistance	Refer to the guided diagnostic program for this code on the approved diagnostic system.
B1D4013	Electrical circuit for connecting the light switch	Light switch wiring circuit: open circuit	Refer to the guided diagnostic program for this code on the approved diagnostic system. Refer to the electrical guides and check the switch circuit. Replace/repair as necessary.
U1A1449	CAN initialization failure	Internal electronic malfunction	Check the electrical power and ground circuits of the unit. Refer to the electrical equipment manual. Configure the module(s) using the approved diagnostic system. If in doubt about the serviceability of the module, refer to the warranty policy and procedures manual.