Range Rover Parasitic Battery Drain: Modules That Won't Sleep

Modern Range Rovers contain over 60 networked control modules. After the ignition is switched off, these modules are supposed to enter a low-power sleep state within 15 to 20 minutes. When one or more modules fail to sleep, they continue drawing current from the battery around the clock. A healthy Range Rover should draw less than 50 milliamps at rest. A single non-sleeping module can draw 500mA to 3A — enough to flatten a battery in 24 to 48 hours.

Short Answer

Parasitic battery drain on Range Rover and Range Rover Sport models is caused by control modules that do not transition to sleep mode after the vehicle is locked and left. The most common offenders are the infotainment head unit (ICM/InControl Touch Pro), the telematics module (TPMS/TCU), the rear camera module, and the Terrain Response control unit. The root causes include software bugs requiring module re-programming, failed CAN bus wake-up signals from faulty door latches or boot lid switches, and aftermarket accessories wired incorrectly into always-live circuits. Diagnosis requires a current clamp measurement over a 30-minute shutdown cycle combined with JLR SDD/Pathfinder module sleep status monitoring. Replacing the battery without tracing the drain is a waste of money — the new battery will drain just as fast.

What You'll Learn

• How the Range Rover CAN bus sleep/wake cycle works
• Which modules are the most common parasitic drain offenders
• How to distinguish between a genuine parasitic drain and a dying battery
• The diagnostic process for tracing a drain to a specific module
• Why software updates and module re-programming often fix the problem
• The role of aftermarket accessories in preventing module sleep

Real-World Scenarios

Case 1: L405 Range Rover Vogue — Flat Battery Every 3 Days

A 2017 L405 Range Rover Vogue came in with a recurring flat battery. The owner had already replaced the battery twice in 12 months — £380 each time at a main dealer. The problem persisted. We performed a parasitic drain test using a DC current clamp on the negative battery cable. After locking the vehicle and waiting for the network to sleep, the resting current stabilised at 1.8A — approximately 36 times higher than acceptable. Using JLR SDD, we monitored module sleep status across the CAN network. The infotainment head unit (InControl Touch Pro) was remaining fully awake. The module was not responding to network sleep commands. A software reflash of the ICM with the latest JLR calibration file resolved the issue. Resting current dropped to 35mA. Total cost: £280 for diagnostic time and software update. The two unnecessary battery replacements had already cost the owner £760.

Case 2: L494 Range Rover Sport — Drain After Dashcam Installation

A 2019 Range Rover Sport had a parasitic drain that started exactly when the owner had a dashcam professionally installed by a car audio shop. The shop had wired the dashcam's permanent live feed into the interior fuse box using an add-a-fuse adapter on a CAN bus-monitored circuit. The constant current draw on that circuit prevented the body control module from recognising that all consumers were off, so it never issued the sleep command to the rest of the network. The entire vehicle stayed awake. We rewired the dashcam to a dedicated always-live circuit that is not CAN-monitored (the OBD port auxiliary power pin). The BCM immediately began sleeping correctly. Resting current: 42mA. No parts required — just 1.5 hours of diagnostic time and rewiring at £220.

Case 3: L322 Range Rover — Intermittent Drain Traced to Boot Latch

A 2012 L322 Range Rover with 98,000 miles had an intermittent flat battery — sometimes fine for a week, sometimes flat overnight. Intermittent drains are the hardest to diagnose because the fault may not be present during testing. We fitted a data-logging current recorder to the battery negative cable and returned the car to the owner for one week. The data showed normal sleep patterns on most days, but on three occasions, the vehicle woke itself at 2am to 4am and stayed awake for 6 to 8 hours. The wake-up trigger was traced to the rear tailgate latch microswitch. Temperature changes overnight were causing the latch to momentarily register as "open," sending a CAN wake-up signal to the entire network. Every module powered up, the interior lights illuminated briefly, and the network failed to fully re-sleep afterwards due to a software timeout bug. Latch replacement (£85) and a BCM software update resolved the issue permanently.

Why Inspection and Diagnostics Matter

Parasitic drain diagnosis on a modern Range Rover is not a job for a multimeter and guesswork. The vehicle's CAN bus architecture means that removing fuses to isolate circuits — the traditional approach — can itself cause modules to wake up and generate false readings. The correct method requires JLR-specific tools that can monitor network activity, module sleep states, and wake-up sources in real time.

At Nine Torque, we use JLR SDD/Pathfinder alongside calibrated DC current clamps and data loggers. For intermittent drains, we deploy week-long current logging equipment that the owner drives away with. This captures the exact timestamp and magnitude of every drain event, which we then cross-reference against CAN bus wake-up logs stored in the BCM.

We also check battery health as a first step. An AGM battery that has been deeply discharged multiple times may have permanent capacity loss — even after fixing the drain, the battery may no longer hold sufficient charge. We test battery state-of-health using a conductance tester and advise on replacement only when the battery has genuinely degraded beyond recovery.

If your Range Rover keeps going flat, stop replacing batteries and contact us for a proper parasitic drain investigation.

Frequently Asked Questions

How long should a Range Rover battery last?

With a healthy electrical system and no parasitic drains, a Range Rover AGM battery should last 4 to 6 years. If you are replacing batteries more frequently than every 3 years, there is almost certainly an underlying drain or charging system fault. Do not keep replacing batteries without investigating the cause.

What is a normal parasitic draw on a Range Rover?

A healthy modern Range Rover should draw between 30mA and 50mA once all modules have entered sleep mode. This process takes 15 to 20 minutes after the vehicle is locked with the key fob (not just the ignition turned off — the doors must be locked). Anything above 80mA indicates a module is not sleeping correctly. Above 500mA, the battery will be flat within 48 hours.

Can a software update fix a parasitic drain?

Yes, frequently. JLR releases software calibration updates that specifically address module sleep behaviour. The infotainment system, telematics module, and body control module are the most commonly updated. At Nine Torque, we check for outstanding software updates on every JLR vehicle that comes in with an electrical complaint. A 30-minute software reflash has fixed more battery drain issues in our workshop than any other single intervention.

Will disconnecting the battery when parked solve the problem?

It will prevent the battery from going flat, but it is not a solution — it is a workaround that masks the underlying fault. Disconnecting the battery also resets module adaptation values, clears radio presets, and can trigger fault codes on reconnection. Some JLR models require a battery registration procedure after reconnection using SDD. Fix the drain properly rather than managing the symptom.

Do aftermarket accessories cause battery drain on Range Rovers?

They are one of the most common causes we see. Dashcams, trackers, aftermarket stereo amplifiers, and phone charging cradles wired into the wrong circuits can prevent the CAN bus network from entering sleep mode. The issue is not the accessory itself drawing current — it is the fact that the current draw on a monitored circuit tells the BCM that a consumer is still active, blocking the entire network sleep sequence. Any aftermarket accessory must be wired to a non-CAN-monitored circuit or use a dedicated timer relay to cut power after engine-off.