Chart A-1 No Service Engine Soon Light

PCM Power Supply And Diagnostic Circuit Diagram:

CIRCUIT DESCRIPTION
The SES light gets power whenever the ignition is turned "ON" and illuminates when the PCM completes the circuit to ground. The light should illuminate whenever the ignition is "ON" and the engine is not running. The light should go out after the engine is started, and stay out unless a malfunction is present.

TEST DESCRIPTION

Chart A-1, No "Service Engine Soon" Light:

Numbers below refer to circled numbers on the diagnostic chart.

1. If 20A fuse for circuit 480 is blown (in fuse holder - continuous battery fuse), check also fuel pump relay and oil pressure switch (see Code 54.)
2. Using a test light connected to battery power, probe each of the PCM ground circuits to make sure connections are OK. See COMPUTERS AND CONTROL SYSTEMS/DIAGRAMS/ELECTRICAL for PCM wiring diagrams and connector/terminal identification.