Engine Controls - Tests W/Codes - Testing: Self-Diagnostics

NOTE: For identification of terminals and wire colors reference in the following testing, see appropriate wiring diagram in SYSTEM WIRING DIAGRAMS B2500, SYSTEM WIRING DIAGRAMS B3000 or SYSTEM WIRING DIAGRAMS B4000 article. For connector terminal identification, see CONNECTOR IDENTIFICATION in TESTS W/CODES - INTRODUCTION article.

CAUTION: Ensure ignition is off before disconnecting harness connector from any component or control module. If PCM replacement is recommended in following testing, always ensure PCM connectors and ground circuits are okay. If either are suspect, repair and repeat testing to confirm PCM malfunction.

NOTE: Perform the following test procedures only when directed during quick test of when referenced by other testing procedures. See QUICK TEST in TESTS W/CODES - INTRODUCTION article. For following tests, use of New Generation Star (NGS) tester is recommended. NGS tester is referred to as scan tool.