My iPhone or iPad doesn't see the adapter

If you are looking at Settings - Bluetooth on your iPhone/iPad, you won't see the device indeed. Bluetooth Low Energy (BLE) doesn't behave like traditional bluetooth, there is no pairing with the phone, the pairing happens from the app when needed.

My adapter's blue light flashes continously and the app doesn't connect

It is likely your adapter is suffering from bad case design, see here for more details: Adapter Fix

I don't tinker with my car, do I need this ?

Even if you're not a mechanic, the app could indeed be useful to you. The MIL light has just come on but it won't tell you what's wrong, the app can and this could be useful, even to a recovery man (or woman) who most likely won't have any diagnostics capability at all. Cars with ECUs are great at hiding problems, a faulty water temperature sensor won't necessarily stop the car from working, the ECU will do its best to manage without it, however the car won't be running as well as it should, the app can tell you a sensor is faulty.

Whether you drive your car occasionally or regularly, you may not realise it is slowly loosing power, or that a throttle potentiometer isn't working but the ECU is making up for it. Why not check from time to time that all is well, even if you take the car to a specialist for a fix, knowing both throttle potentiometers are working and in sync, adaptives aren't off the scale leading to rich or lean running which isn't good for your engine, lambda sensors working as they should, any of these things could go wrong and you won't know until the next service unless you have a way of interrogating the ECU.

You could also run the app after a service to make sure all is well.

I have two (or more) TVRs, how does it work ?

You can either transfer the Bluetooth-Serial adapter from car to car, or install one in each car. The app will seamlessly connect to whichever is powered up, if both are powered up at the same time, the app should connect to the nearest one although there is no guarantee.

Where is this ECU serial connection ?

If you have never needed to connect a computer or other diagnostic tool to your ECU, you may need a few other bits and pieces. Firstly (on a Cerbera), lift the carpet in front of the passenger seat and gently pull the bottom of the panel nearest the passenger's feet towards you. I say gently because my ECU is velcroed onto the panel and the cabling to the ECU isn't very long... I don't know where the ECU is located on Tuscans, Sagaris, Tamora and T350 cars, sorry.

Once you have done this, you should find an anodised box, roughly five inches square and 1.5 inches thick, this is your ECU. Next you need to identify if you have the later ECUs with the three pin diagnostics cable, or the earlier one with the serial connector inside the ECU.

3 Pin diagnostics (Usually found on Speed 6 cars, however my V8 has this type of connection)

Follow the wiring from the large connector at the ECU and look for three wires floating about with a black three pin connector on the end (picture here: https://www.pistonheads.com/gassing/topic.asp?t=1286401). If you have this, you'll need to make or order a serial cable.

To make it: https://www.pistonheads.com/gassing/topic.asp?t=1286401

To order it (data lead from TVR Parts - there may be other suppliers): https://tvr-parts.com/tvr-parts/part-details/tvr-rp004/data-lead

Onboard Serial Connection

Some ECUs have a serial connector soldered onto the ECU's circuit board, if you've not found the 3 pin connector above, you'll now have to open your ECU to find this connector. There are several discussions on PistonHeads on this topic, some have made a hole in the top of the ECU cover in order to gain permanent access to the connector for example.

So, unless you are looking for a longer term solution (cable permanently in place), you can simply plug the Serial-Bluetooth adapter onto the ECU's serial port and power the adapter up through USB or otherwise. For a longer term solution, it would be best fit a serial cable and the adapter at the end of that cable. The cable you would need is http://www.maplin.co.uk/p/serial-rs232-9-pin-male-to-9-pin-female-3m-web-only-l67bt or https://tvr-parts.com/tvr-parts/part-details/tvr-l67bt/data-lead if you want the genuine (and more expensive) article.

I have two (or more) iOS devices, do I need to purchase the app for each ?

No, so long as they share the same apple id, once you have purchased the app, you can install it on any number of devices. The app is also compatible with iPhone and iPad, so unlike some apps there is no need to purchase it twice should you want to run it on an iPhone and iPad. The only requirement is that the iOS devices have at least iOS 10.3 installed.