The Active Noise Cancellation will stop working, causing noticeable engine drone or hum inside the cabin, particularly at highway speeds.
Points directly to the Engine Speed Input circuit. Modern Land Rover audio amplifiers require real-time engine speed (RPM / Crank signal) for active noise cancellation (ANC), volume compensation, and system power management.
Once you have resolved the B1D9F-11 fault, consider these measures to prevent it from returning:
B1D9F-13- Engine Speed Input- circuit open (2B) - fullfatrr.com land rover b1d9f-11
Locate the Audio Amplifier Module. In most Range Rover models, it is positioned in the left or right rear quarter panel trunk cavity behind the carpet trim. Unplug the main harness connector and inspect the pins for green copper oxidation or bent metal teeth. Step 3: Multimeter Testing (Harness Side) Set your digital multimeter to the setting. Place one probe on a verified clean chassis ground point.
Professional diagnosis is recommended due to the complexity of the InControl Touch Pro and MOST (Media Oriented Systems Transport) fiber optic networks.
Vehicles equipped with panoramic sunroofs (like the Range Rover L405) can suffer from clogged sunroof drain tubes. When rainwater backs up, it drains down the A-pillars directly into the floor wells. This pools around the amplifier, its ground blocks, and its wire harness connectors, creating an electrical short circuit. 3. Low Battery Voltage Fluctuation The Active Noise Cancellation will stop working, causing
Breaks, pinches, or chafing along the CAN-bus communication lines connecting the engine management network to the cabin infotainment hub.
It is common for DIY mechanics to look at an audio amplifier fault code involving "Engine Speed" and assume it is a diagnostic tool error. However, the Audio Amplifier Module requires an active engine RPM signal for two primary features:
[Connect JLR Diagnostic Tool] ──► [Is Code Active/Permanent?] │ ┌─────┴─────┐ YES NO │ └───► Clear Intermittent Code & Test Battery [Check Wiring Harness] │ ┌──────────────┴──────────────┐ Fault Found No Damage Visible │ │ ▼ ▼ [Repair Harness/Pins] [Test Back of AAM Pins] │ ┌─────────┴─────────┐ Short Found Internal Short │ │ ▼ ▼ [Isolate Circuit] [Replace Amplifier] Step 1: Preliminary Battery and Voltage Check Once you have resolved the B1D9F-11 fault, consider
If you plan to fix this yourself, let me know the of your Land Rover, and if you are noticing any cabin noise issues . I can provide the precise amplifier location for your vehicle spec. Share public link
If cleaning grounds and ensuring a healthy battery does not resolve the code, the amplifier itself is likely faulty. Replace the AAM with a new or known-good unit. Crucially , a new amplifier will need to be programmed and configured to the vehicle using a Land Rover-approved diagnostic tool. This is not a simple "plug-and-play" procedure.