Data Link Connector: Description and Operation

Diagnostic Connector (STO/STI):

STI And STO Connectors:

PURPOSE
The Self Test Output (STO) and the Self Test Input (STI) connectors are used when performing the Electronic Engine Control (EEC) Quick Test diagnostic procedure with either a scan tool, analog voltmeter, or jumper wire.

OPERATION
When the STI connector is jumped to ground, a signal is sent to the Powertrain Control Module (PCM) activating PCM Self Test mode. The STO connector receives output signals from the PCM that appear as numbered codes on the scan tool, needle sweeps on the analog voltmeter, or flashes from the MIL. Codes retrieved from PCM memory represents a malfunction within the EEC system.