To reduce the risk of personal injury and/or damage of electric and electronic components, always observe the following:

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Always switch ignition off before connecting or disconnecting test/measurement tools.
It is possible that the control module will recognize a malfunction and store a DTC during some tests. After completing all tests and repairs, DTC memory should therefore be checked and erased if necessary.
Always switch ignition off before disconnecting or connecting battery. Failure to do so may damage electronic control modules.