Land Rover B109c-15

A very common cause for this code is replacing factory halogen bulbs with low-quality or incompatible "logo" puddle lights. These can trigger an electrical error in the door module.

| Model Year | Common Fix | |------------|-------------| | 2006-2012 Range Rover Sport | Replace bulb (WY21W) + clean socket | | 2013-2017 Range Rover (L405) | Check for water in headlight connector | | 2012-2018 Evoque (L538) | Corroded side indicator repeater | | 2005-2009 LR3 / Discovery 3 | Bad ground G104 (left inner fender) |

For the uninitiated, a modern Land Rover is the pinnacle of British engineering—a luxurious chariot capable of crossing continents or navigating the school run with equal poise. But for those who own and maintain these sophisticated machines, the relationship is often a bit more complex. Beneath the veneer of Walnut wood and Windsor leather lies a network of sensitive electronics that, while brilliant when functional, can turn a routine drive into a headache.

To understand the code, you must break it down into two parts: the and the Fault Type (15) . land rover b109c-15

Even if the lamp is dry, the multi-pin connector at the rear of the lamp assembly is exposed to road spray. Salt and moisture cause green corrosion on pins 2 or 3 (the turn signal feed). This corrosion changes the voltage drop, triggering the B109C-15 logic.

: Vibrations or previous interior work can lead to loose pins in the PDM or overhead console. Recommended Diagnostic Steps Land Rover Discovery Diagnostic Report | PDF - Scribd

Multimeter, trim removal tools, electrical contact cleaner, JLR-compatible diagnostic scanner (Gap IIDTool, Autel, or SDD). A very common cause for this code is

: Check the wiring harness where it passes through the door bellows. This area is prone to wire fatigue or breaks which can cause an "open" circuit.

Check the electrical connectors at the door module (DDM/PDM) for green oxidation or bent pins. Cleaning them with an electrical contact cleaner can sometimes restore the connection.

: In some cases, the Door Module temporarily disables the circuit after a change. Simply closing the doors, locking the vehicle, and then re-opening can reset the module and restore light. But for those who own and maintain these

Unlike a simple "bulb out" code (which is usually a Type 02), the B109C-15 suggests a more complex electrical anomaly that the BCM cannot rectify.

: This code frequently appears after swapping standard halogen bulbs for LED units or "logo" puddle lights. Many aftermarket LEDs do not have the correct resistance, causing the Door Module to detect a circuit fault.

This code is usually stored in the or the Passenger Door Module (PDM) . Common Symptoms

Set your meter to DC Volts (20V scale).