Symptom Driven Diagnostic (SDD) – Diagnostic Adapter

6 min read

Land Rovers of a certain age eventually cry out for a diagnostic session. With dealer diagnostic sessions costing as much as £145 per hour, you may want to DIY. This will put you on the slippery slope of the Land Rover Symptom Driven Diagnostic (SDD) system and diagnostic adapter.

In this series of articles, we will take a look at the hardware and software required to get up and running with SDD. Let’s start with a brief overview and a look at the SDD diagnostic adapter.

What is Symptom Driven Diagnostics (SDD)?

At their simplest, modern cars are simply a collection of computers strapped to some wheels. They are typically on the cusp of a breakdown. Emissions controls, safety requirements and infotainment systems mean each of these ECUs will be connected to a myriad of electronic sensors. The sensors give more vehicle system control, more features and a whole new way for cars to breakdown. Fortunately, they also provide a wealth of information and an opportunity for ECUs to tell you how they are feeling.

To talk to these ECUs and understand what ails them, we need a way to talk there language. All vehicle manufactures have some sort of proprietary system to talk to their products, including Land Rover.

Hardware and Software for SDD

The Freelander2 was designed to use the Symptom Driven Diagnostic (SDD) system for communication and fault investigation. SDD is built off the back of the Ford-based IDD tool and covers cars from about 2005 to 2018. More modern vehicles use the Pathfinder system and DOIP (diagnostic over internet protocol) communication while SDD uses CANBus.

The complete system consists of a USB diagnostic adapter, software running on a PC and an optional connection to the online diagnostic server. Typically SDD should also be used with some form of battery support unit. Let’s have a look at our options for each of these components

SDD Diagnostic Adapters

Over the 15 years of Land Rover production that SDD has supported, a number of genuine SDD diagnostic adapters have been available. As is typical of the automotive field, some of these adapters have been cloned. What options are there and what are the merits, let’s have a look.

Mongoose (Genuine and Clone)

Mongoose (Clone)
Mongoose (Clone)

The oldest of the common adapters are the ‘Mongoose’ USB adapter. For a long time, this was available from Land Rover and was the common tool for use with IDD. The adapter is small and compact but not the fastest hardware and not capable of all functions of the newer adapters.

The Mongoose is also the most readily available cloned adapter and is reportedly quite reliable, probably a result of how long it has been copied for. There are however some terrible copies which are almost guaranteed to cause issues. I can’t find genuine Mongoose adapters for sale any more, but clones can be picked up from as little as £33.


Land Rover VXDiag - VCX Nano
Land Rover VXDiag – VCX Nano

The well-polished presentation of the VXDiag VCX Nano seems to hide a box of magic tricks that has a variable performance. The same adapter can, by way of a license from the supplier, be used on multiple vehicle types. It should be noted that this isn’t a clone of a recognised product but simulates the performance of a genuine Land Rover tool

My own experience with the Land Rover version wasn’t great. I managed to pick one up very cheaply, just over £40, and quite literally put it in the bin a few months later. It was so unreliable. Just watching the can traffic you could see it creating bus errors. It’s probably okay for fault code reading and maybe learning your way around SDD, but I wouldn’t trust driving with it plugged in let alone making changes.

It’s maybe just a bad unit, the supplier wasn’t interested in supporting and they are known to have a range of designs and quality. I use a Volkswagen version of the VXDiag which is far more reliable and doesn’t cause bus errors. But even then I shelled out on the more reliable but limited VagCOM.

VCI (Genuine and Clone)

VCI adapter (Clone)
VCI adapter (Clone)

The VCI (Vehicle Communication) interface from Diagnostic Associates is the main tool used in dealerships. Its fly lead means you don’t have a cumbersome brick stuck in the OBD port and the case is incredibly rugged. Even a Range Rover Autobiography won’t crush it, not that I’ve tried. It may feel a little on the pricey side at £400 but it’s a well-proven tool.

Again clones of this tool care available. The internal pictures I’ve seen of one clone suggest most of the cost-cutting is in component quality. There doesn’t look to be any electrical isolation between USB and vehicle. I’ve not had one in my hand but based on the pictures, I’d be cautious about plugging it into my laptop! The VCI clones are normally obvious by the lack of Jaguar and LandRover branding.

DA-Dongle (J2534)

DA-Dongle - J2534
DA-Dongle – J2534

The DA-Dongle also from Diagnostic Associates is, in my experience, the best option for using with SDD and its what I use from day to day. It is a simple no-frills unit that was developed for and is approved by Land Rover.

The cost, £200, may seem high, but it is the cheapest genuine adapter. It could give the reliability that saves money in the long run. Despite its age, it is still supported by Diagnostic Associates (for Land Rover) and has recently received some additional functionality. It does not have all of the features of the VCI, but I’m yet to find any real limitation.

Other Genuine Adapters


There are a handful of other genuine adapters out there outside of the needs of a hobbyist. Diagnostic Associates have the ST512 which can be used as a DA Dongle, but can be used stand-alone saving the need for a separate laptop. It is currently priced at £610.

The DOIP VCI is the current Land Rover dealer tool capable of working with the most recent vehicles using SDD or Pathfinder. It is ruggedized like the VCI and includes a stand-alone onscreen control like the ST512.

The Danger of Clone Adapters

Cloned hardware is dangerous and simply not worth the risk.
But they are also very cheap and positively tempting when you just want to get a car running again. I’ve taken apart both genuine and cloned adapters from a range of suppliers and seen horror stories on both sides.

Typically cloned adapters use cheap components on hastily un-testing custom PCBs and cut costs by taking out isolation. The isolation stops the 5v USB connector on the PC from seeing the full 16v+ cranking voltage on the car. I’ve also seen poorly implemented cloned tools putting spurious messages on to a CAN Bus, resulting in a complete network lock up.

When choosing an SDD diagnostic adapter, you need to weigh up the risks for your self. That risk assessment needs to include what you are using the cloned tool for. If you are just looking to read fault codes and maybe interrogate an ECU, then the risk of a cloned tool is very low. At that point, the £33 cloned Mongoose is a good option. But if you want to update software modules or write data to the car, can you afford to have the car off the road? A corrupted ECU could cost thousands to fix.

Ultimately the decision is yours to make, but if I write data to a car, I use a genuine adapter!

What to Read Next?

In the next article, we look at some of the other hardware required for SDD starting with battery support units.

In the meantime, you might want to have a read of the CANBus series of articles.

NEXT: SDD – Battery Support Units


    • Hi Wayne,
      I haven’t created a guide on how to install SDD because, to be honest, it’s really simple.
      The hardest bit is being patient. The files are huge so it takes a long time to download.
      The system is quite old fashioned so it takes a long time to do each segment. For the time being, you can download all the files directly from JLR at DiagnosticCentral. You can then buy a TOPIX subscription from JLR (costs around £3500) or there are alternatives on eBay for about £9. I have installations running on Windows7 and Window10 without a problem.

      • Ok great thanks.
        I’ll download tomorrow.
        I am hoping to carry out a CCF edit to enable heated seats.

          • Yes I have the panel and seats.

            I have checked all wiring and it all appears to be in place.

            I have the extra plugs under the seats and two fuses located in the rear fusebox.


  1. Thank you for this great article, I’m still undecided on what to get between an Autel AP200 and a Mongoose clone. They are both sold from chinese websites but Autel seems like a more reliable brand?

    I’m mostly looking for diagnostics and I do not need to code keys at the moment.

    I just would like to read errors codes. Do you personally thing that the SDD is more precise than standard OBD tools like the AP200 in therms of diagnostics? Or is it just a normal interpretation of the DTC.

    Thank you

    • Hello Amine,
      I don’t have any knowledge of the Autel system. The SDD is the dealer tool, created by Jaguar Land Rover so should have the very best information in it. That said, it doesn’t have a complete list of every DTC and can be very very slow. Even a simple DTC read can take 15 minutes from start to end. Most aftermarket systems can do a DTC read in just a few minutes and have most of the DTC knowledge that SDD has. Personally, if I want to quickly read or clear faults on the Freelander, then I do not use SDD as it takes too long!
      I hope that helps a little.

      • I see, I’ll probably go with a simpler OBD tool like the Autel then.

        Thanks again for taking the time to write this and sharing your knowledge with us M !

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