Jaguar vehicles are the premium cars that many of us want to own. But reports all around the internet show us that these cars are not the icon of reliability anymore.
The “Gearbox Fault” error message in your Jaguar may not mean that the transmission is dead. It can pop up due to a low 12V battery, TCM (transmission control module) malfunctioning, poor wiring or connections, low transmission fluid level, and some other issues.
In this article, I will try to tell you everything I know about the topic and how you can locate and solve the problem on your own to avoid paying hundreds for inspections.
What exactly does the “Gearbox Fault” message mean?
This message is pretty common for older generations of Jaguar vehicles. New cars will be more specific and will most likely show some additional warning lights or messages that will make the inspection quicker and easier.
But even new Jaguar cars still can show this message and spoil your mood, especially if you know how much it costs to repair or replace the transmission in these cars. The message may be general like the Restricted Performance in JLR vehicles.
So, here are the possible reasons for “Gearbox Fault”:
1) Low transmission fluid
The level of fluid is very important for conventional automatic transmissions. With low levels, they just stop working and require immediate top-up.
2) TCU glitch
It was a significant problem for older Jaguar vehicles. TCUs used to hate high humidity and developed glitches in humid weather. The message could go away once the weather is fine.
3) Low battery
It’s not uncommon for a Jaguar car to throw the “Gearbox Fault” message along with other codes and messages when the battery is low and dying. I believe the problem is with the glitch in the TCU again.
4) Engine problems
Surprisingly enough, your Jaguar may start throwing the gearbox message when the engine is not OK. For example, if your engine misfires heavily, loses power, and misbehaves in many other ways, the transmission may get stressed and the sensors may eventually trigger the message about the transmission fault.
Also, I witnessed the case when low-octane fuel caused issues with the engine and led to the gearbox message popping up on the dash.
5) Wiring and connections
The TCU and ECU get readings from dozens of different sensors. Once one sensor stops sending data or sends weird readings, the control unit may throw a code and, subsequently, a message on the dash of your car.
6) TCM problem because of water damage
It’s not uncommon for older Jaguars to leak water through the sunroof secretly. It doesn’t leak in the interior but runs all the way down the roof and then may eventually get to the place where the TCU is located. Also, poorly installed windshield may be the reason of leakage.
In some models, the TCU is placed on the driver’s side, in the interior. If it’s damaged by water, there is no other way but replacing it with the new one (or used but well-checked).
7) Actual transmission problem
Fortunately, the transmission issues in Jaguar cars are not as common as all the problems mentioned above. If you are unlucky to get transmission issues, your budget will feel this. Most commonly, these conventional transmissions in Jaguar fail between 120,000 and 200,000 miles (200,000 and 300,000 km).
How can you try and solve this issue?
To solve the problem, you need to locate its root. But in this article, I’m going to show you several DIY methods that will help you try your luck and solve the issue on your own without even going to the dealership or garage.
Check out my solutions for the transmission-related message in the Freelander – this may help, too.
Here are the things you may want to try once you see the “Gearbox Fault” message in your Jaguar:
1) Checking and charging the battery
This is probably the easiest thing you can do. First, check if the battery shows about 12.5 volts when the engine is off. After that, start the engine and measure the voltage on the battery terminals – it should be higher than 14 volts because the alternator now should charge the battery.
You may check this using a simple multimeter – just any model. If the battery voltage is too low, you may be sure the problem is exactly in the voltage. Charge the battery or replace it with a new one.
Unfortunately, just jumping the battery won’t help. It needs proper charging. And if the 12V battery in your Jaguar is older than 5 years, you should replace it once it starts malfunctioning.
2) Reset the control units
As you already know, the gearbox message may pop up on the dash of your car when the transmission control unit malfunctions or has a glitch. In this case, you may try solving the problem by resetting the control unit.
For this, you may pull out the fuse that powers the corresponding control unit. But I recommend the battery-disconnection method.
Here’s what you should do: disconnect the cable from the negative terminal, then from the positive one, leave the car for several minutes, and connect the positive terminal then the negative one. You may press the honk before reconnecting the battery to make sure there is no power left in the system.
This will help you reset the system and the TCU may eventually start working properly.
3) Check and add transmission fluid
If you have the kind of transmission with the dipstick in it, you can check the level of the fluid on your own and even top up the fluid through the dipstick hole. It’s not easy but it’s still possible.
If you tried everything else and only suspect the low fluid in your transmission, you can go to any garage and they will check the level without charging you much. Of course, if the fluid is low, you need to find the reason – a leak, for example.
4) Clean the contacts on the TCU and ECU
While the TCU (also called TCM) is one of the obvious culprits, you may start with it. The control unit is usually located on the left side of the car, just where the foot of the front passenger for right-hand cars or driver for left-hand cars is located.
You will need to take a ton of plastic trim to get to the transmission control module. Make sure it’s not affected by water. Disconnect it and see if there is a visual presence of corrosion on the connections.
Clean the connections and think of some water shield for it to avoid further damage. This is worth trying if other solutions don’t help you.
5) Scan the codes in all control modules
For this, you will need a good scanner. Not just a cheap ELM scanner for 20 pounds but a professional scanner compatible with your vehicle. Fortunately, some car part stores and garages can give it to you or help you scan the car for little money or even for free.
So, your task is to read the codes in the ECU – engine control unit and also the TCU – transmission control unit. Write down the codes, google their meaning and possible reasons, and then deduct what may have happened with the car.
I once saw a Jaguar throwing the “Gearbox Fault” message because of the P0300 code in the ECU which means “multiple cylinder misfire”. Once the problem with the air supply was fixed, the gearbox message went off.
When is it time to ask for professional help?
If you tried everything listed above and still have no idea what causes the “Gearbox Fault” message, please go to a good garage or to the dealership and let professionals do their job. They will scan the vehicle using professional equipment and will locate the problem.
Unfortunately, if nothing else helped, you may be pretty sure that the problem is either with the transmission or with the wiring. If you are lucky enough, you can get some wire or sensor replaced for several pounds/euros. But if the transmission is actually faulty, the bill is going to be heavy.
Can you safely drive with the “Gearbox Fault” message?
No, it’s not safe to drive with this error on the dash in your Jaguar. Unless you know what exactly causes the problem, you may not be sure that the transmission won’t blow making you lose control of the car entirely.
If you happen to see this message, you can still drive but do it carefully and only when necessary. I mean, there is no need to call a tow truck if the car still moves and doesn’t sound weird. Just keep driving slowly and carefully to get the vehicle to the garage or dealership.
It’s an extremely bad idea to tow something in this condition, to drive in a mountainous area, or to put any other stress on your transmission whenever you see this message.
How much is it to repair or replace the Jaguar transmission?
Of course, it highly depends on the year and model of your vehicle. Typically, the older cars use a conventional automatic transmission that is possible to repair. However, the price of repair starts at about £2,500 and more depending on the problem.
Alternatively, you may try buying a used or remanufactured transmission on eBay or other platforms. This is risky yet may prove to be lucrative with prices starting at £1,500 for decent units. Don’t forget to include labor prices in your calculations – the minimum of £500 and up to £1,500 depending on the chosen garage.
In newer cars, transmission replacement is often the only option if the unit is found faulty. And, unfortunately, it costs you a fortune to replace such a high-tech transmission – starting with £4,000 for cheaper models and up to £7,000 for some recent types of Jaguar transmissions (including ridiculously expensive dealership labor, of course).
Do you have experience dealing with the “Gearbox Fault” message in your Jaguar? Write in the comments below and let other owners know!