Diagnostic Circuit Check

Diagnostic Circuit Check:

NOTE: Check and correct any problems with vacuum hoses, electrical harness connections and routing before proceeding with this check.

The Diagnostic Circuit Check ensures that the on-board diagnostic system is functioning, determines the trouble codes to be displayed and guides diagnosis to other problem areas.

"CHECK ENGINE" LIGHT

The "Check Engine" light will only come "ON" if a malfunction occurs under specified conditions while the engine is running. If the malfunction clears, the light will go out and a trouble code will set in the ECM. If the light comes "ON" intermittently and no code is stored, see "INTERMITTENT 'CHECK ENGINE' LIGHT" under ON-BOARD DIAGNOSTICS. Any codes stored will be deleted from memory if the problem does not recur within 50 engine starts.

If the "Check Engine" light is inoperative (does not light when the ignition is switched "ON"), first check the ECM power fuse and replace if blown. If further troubleshooting is required, refer to "CHECK ENGINE" LIGHT under DIAGNOSTIC CHARTS.