Diagnostic Circuit Check Determines The Following:
WARNING: This page is about a different variant/trim than selected.
- Whether Malfunction Indicator Light (MIL) works.
- Whether ECM/PCM/VCM/VCM-A is operating and can recognize a fault.
- Whether any codes are stored.
After performing basic diagnostic procedures listed under PRELIMINARY INSPECTION & ADJUSTMENTS; A-7, BASIC FUEL SYSTEM CHECKS and C-4, BASIC IGNITION SYSTEM CHECKS, use self-diagnostic system for determining computer-related problems. See Figure.
If codes are NOT indicated and driveability problems still exist after performing necessary tests in diagnostic circuit check, see TESTS W/O CODES - GASOLINE article and SCAN TESTER USAGE under SELF-DIAGNOSTIC SYSTEM in TESTS W/CODES - 5.7L article.
- Check MIL operation. Turn ignition on with scan tester not connected, DLC terminal not grounded and engine not running. MIL should be on steadily. If light glows and stays on steadily, go to next step. If light does not glow, go to A-1, MALFUNCTION INDICATOR LIGHT (MIL) INOPERATIVE. If light flashes, go to step 3).
- Ground DLC test terminal "B". MIL should flash Code 12, followed by any codes stored in PCM memory. If light goes from bright to dim or if light remains on and does not flash Code 12, see A-2, MALFUNCTION INDICATOR LIGHT (MIL) ALWAYS ON OR WON'T FLASH CODE 12.
- Check for short to ground in diagnostic test terminal wire between DLC terminal "B" and PCM terminal. See Fig 1. If circuit is okay, replace PCM.