As an IT/electronics buff I have always been a bit wary of plugging any of these devices into the diagnostic socket. I can happily take a PC to bits and rebuild the hardware and software from the bios up but I am never sure how "passive" these code readers are. A few years ago a friend was playing round with some device on his Audi and it completely screwed up his ecu and the car wouldn't start and had to be towed to a dealer who managed to reprogram it for £lots. Perhaps I need to read up on CAN busses etc.
Has anyone any negative experiences of using these devices or am I just being paranoid?

The only negative I have ever had with my code reader was on the subaru I had
I unplugged the OBD lead before exiting and every dash lamp came on and stayed on
Warning info high beam temp alarms the lot, like a bulb test.
I reconnected and cleared the error code, all lamps exitinguished and no harm done.

Just had this warning come up and took it to Harwoods Landrover dealers and at no charge they reset the service interval warning light. This is nothing to do with the oils becoming diluted by another substance at all it is simply a timed service interval light that was not reset properly when my car had a full service 7 months ago.

Clarification

Just had this warning come up and took it to Harwoods Landrover dealers and at no charge they reset the service interval warning light. This is nothing to do with the oils becoming diluted by another substance at all it is simply a timed service interval light that was not reset properly when my car had a full service 7 months ago.


Agree with above post, was at dealers today and asked about this "oil service" message. Service guy said it's based on number of days after being reset and nothing to do with DPF regenerations. 11 GS Bali Blue
07 GS FL2. Usually muddy. Gone
Numerous LRs since 1963

You can reset the "oil service" 2011 with DPF Yourself its just a matter of
1. Key in ignition slot
2. Hold down trip mileage button
3. Push ignition button (dash lights come on) & oil service message starts flashing
4. Scroll through "date" "mileage" then "reset" end