Editing On board diagnostics (section)

==DIY==
[[Image:OBDII_111R.jpg|thumb|left|OBDII Connector, S2 111R]]
[[Image:OBDII.jpg|thumb|left|OBDII Connector, S2 Exige]]
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On the S2 Elise it is quite simple to connect to the cars [[ECU]] yourself.

Until 2008 all S2's can be queried using the ISO 9141-2 OBD II protocol for the OBD required error codes and results.
From 2008 onwards CAN is the only permitted OBD2 protocol.

All S2 variants also have a CAN bus connection on the same diagnostic connector.

For the Rover powered S2 variants the CAN bus is only connected to the engine ECU and used by the Lotus scan tool to reflash/upgrade the ECU and obtain the ECU dump information at the first service.

The dash unit still uses discrete inputs for the various gauges and information readouts, either connecting directly to sensors or using PWM signals from the ECU.

The Toyota powered S2 (111R, Fed-Elise, Exige2)  also connects the CAN bus (running at 1 megabit/s) to the dash unit and does away with most of the discrete inputs to the dash unit, RPM, speed, MIL/CEL, coolant temperature and fuel level are supplied via the CAN Bus, the rest are discreete inputs.  

The ScanTool3 provides the ECU reflash and DUMP via the K line, using the L line as an enable latch, the CAN bus is not used for reflashing or ECU dump, though it can be used by Lotus with their internal EFi supplied mapping tools.

Lotus has a tool called Lotus 20/20. What Lotus 20/20 can do...

Read general vehicle data** — It displays ECU (engine-control unit) information: part numbers, emissions-related data, VIN, and other core vehicle metadata.
Read and clear diagnostic trouble codes (DTCs)** — You can scan all vehicle systems (engine, transmission / TCU, ABS, SRS/airbag on many models) for fault codes, and clear them.
Flash / program certain control units** — For supported cars (most 2007+ Lotus, with exceptions), you can re-flash or update firmware/software for at least the Engine Management System (EMS), Transmission Control Unit (TCU), and ABS.
Adjust some configuration via instrument pack (on supported cars)

Limitations / What it doesn’t reliably do (or may depend on model/access level)

* The version available to consumers/enthusiasts (“Independent Retailers” licence) is **limited** compared to the full dealer version. 
* It apparently **does not support live data streaming** (e.g. reading live sensor data like transmission temperature for maintenance) 
* Some modules (for example SRS/airbag) may use different communications protocols (e.g. K-Line rather than CAN), which could make them harder to access depending on adapter and vehicle model.

What you need to run 20/20

* A Windows-based laptop + a **J2534 pass-through adapter** to connect to the car’s OBD-port
* A valid Lotus-issued licence/subscription key — software won’t run without it.

🧰 Typical Use Cases

* Clearing fault codes after maintenance or repairs.
* Flashing updated firmware/software for EMS, TCU or ABS (e.g. after parts replacement).
* Checking VIN, part numbers, emissions data — useful for verifying the vehicle’s configuration.
* Adjusting some vehicle configuration bits.