Diagnostic Circuit Check

Chart I.:

PCM Wiring:

Scan Tool Hookup To ALDL Connector.:

DESCRIPTION

The diagnostic circuit check is always the starting point for any malfunction code or driveability problem. This check verifies the PCM's on board diagnostics are functioning properly. While performing a diagnostic circuit check, record codes and flags for use in diagnosing possible sub-system failures.

OPERATION

Key, "ON" - Engine "OFF" SES telltale should be "ON" steady.

When ALDL connector Pin B is grounded to Pin A with Key "ON" - Engine "OFF" diagnostic mode is entered.

^ Code 12 will flash the SES indicating diagnostic communication.

^ Code 12 will flash three times followed by any other Engine Codes (EC) that may be stored.

^ If code 12 is not indicated, a problem is present within the diagnostic system itself.

^ Code 11 will be displayed LAST to indicate if there are any Transmission Codes (TC) stored in memory. The TC codes will flash on the "SHIFT TO D2" lamp or the "HOT" lamp.


NOTE: Do not operate the vehicle for a prolonged period of time in this mode. Damage to the Catalytic Converter may result.

DIAGNOSTIC AIDS

The following circuits are energized when the vehicle enters diagnostic mode:

^ Cooling fan is turned "ON".

^ IACV is pulsed in and out.

^ EVO is cycled.

^ CCP is cycled "ON".

^ EGR is cycled "ON".

^ Hot telltale turned "ON".