5 Signs of a Failing JLR Telematics Module (TCU)

Is Your JLR's Connectivity on the Fritz? 5 Signs of a Failing TCU

When the Telematics Control Unit (TCU) in your Jaguar or Land Rover starts to fail, the symptoms can range from minor annoyances to critical safety warnings. Recognizing these signs early can help you diagnose the problem correctly. Here are the five most common symptoms of a failing JLR TCU.

1. ‘SOS System Inactive' Warning

This is the most definitive sign of a TCU fault. This message on your instrument cluster means the module has failed its self-check, and the automatic emergency call function will not work in a crash. This is often caused by the failure of the TCU's internal, non-serviceable backup battery.

2. InControl Remote App Not Working

If you can no longer lock your doors, check your vehicle status, or use the remote start function from your smartphone app, the TCU is likely offline. It's the sole communication link between the app and your vehicle.

3. No GPS or ‘Last Known Location' Shown

A failing TCU can lose its ability to acquire a GPS signal. You'll notice this if the vehicle's own navigation system shows an incorrect location or if the Remote app only shows the car's ‘last known location' instead of its current one.

4. No 3G/4G/LTE Signal Icon

Look at your infotainment screen. If the cellular signal icon (similar to your phone's) is missing or constantly shows no bars, it means the TCU is not connecting to the network. This will disable all ‘Live' services, traffic updates, and the Wi-Fi hotspot.

5. Parasitic Battery Drain

In some cases, a faulty TCU can fail to ‘go to sleep' properly when the car is turned off. It remains active, continually drawing power and leading to a dead 12V battery overnight or after a few days. This can be a tricky problem to diagnose, but a TCU should always be a suspect in modern JLR vehicles with unexplained battery drain.

If you're experiencing one or more of these symptoms, a professional diagnosis is needed. More often than not, the solution is a replacement with a new, genuine JLR TCU.