Where could I buy this test clip?
The 3M with gold-plated contacts are the best...
http://de.farnell.com/ic-test-clipsBut sometimes it doesn`t works reliably, because the power from the prommer supplied the circuit with voltage.
So, parts of the circuit will try to run and makes conflicts by accessing the EEPROM.
In some cases it helps to bridge the oscillator quarz.
Last week I have read successfull the EEPROM in my instrument cluster with a clamb, but writing back no chance.