Diagnostic Mode Switch/Connector: Description and Operation

PURPOSE
The Service Check Connector is used to put the Engine Control Module (ECM) and the Transmission Control Module (TCM) (A/T only) into the diagnostic and timing setting modes.

OPERATION
By the shorting together of its two pins a signal is sent to the ECM and TCM placing them into the diagnostic mode.

CONSTRUCTION
It is a two pin connector, which is designed to mate with a factory shorting plug. In the absence of such a shorting connector, it may be used with a length of wire jumped across its two terminals.