The instrument panel cluster (IPC) does not turn ON the SERVICE ENGINE SOON malfunction indicator lamp (MIL). The IPC turns various telltales ON which are related to the detected malfunction. The recommended method for reading DTCs stored in memory, is by using a scan tool plugged into the data link connector (DLC) connector located under the instrument panel on the left side. Follow the scan tool instructions supplied by the tool manufacturer. The DTCs will be stored in the memory of the IPC as a Current or a History DTC.

This section uses diagnostic tables, wiring diagrams and descriptive text in order to direct you in performing specific tests in order to locate and repair the problem. The diagnostic table is a step by step procedure in order to determine the circuit or component that is the source of the problem. The wiring diagrams and the text describing the system, test conditions, failure conditions and actions taken when a DTC is set are located on the page facing the diagnostic table.

Diagnostic trouble codes (DTC)s, when set, indicate that the IPC has detected a malfunction in a particular circuit or other system. Other system malfunctions are generally, but not exclusively, reported to the IPC via the Class 2 data message. The IPC is programmed with routines for internal checks that the IPC follows only under prescribed conditions (called Test Conditions). When these conditions exist, the IPC tests certain circuits or systems for a malfunction. These tests are called failure conditions or conditions for setting the DTC. When these conditions are true, a DTC is set. The IPC may turn a telltale malfunction indicator lamp (MIL) ON. Refer to the applicable DTC Table for procedures and details.

When the IPC determines that the test conditions and the failure conditions for a particular DTC are true and the condition is during the current ignition cycle, the IPC sets the code as a Current DTC. All DTC(s) remain current until the next fault free ignition cycle and the IPC finds the test conditions are true and the failure conditions are false. The Current code then will become a History code only.

When a DTC reports a failure and the failure was not in the current ignition cycle the DTC will be stored as a History code. The IPC performs internal diagnostic tests in order to acknowledge that the related systems have reported a pass or fail condition. Each diagnostic test that fails is recorded in the IPC memory. The IPC memory can be accessed with a scan tool to determine which DTC circuit was at fault.

A history DTC can be cleared (for any diagnostic test) as follows:

After diagnosing a problem, in addition to repairing the discovered malfunction, clear any DTC(s) set. Verify that there is proper operation. In order to verify proper operation, you must duplicate the conditions when the customer's comment occurred or if a DTC was set, you must duplicate the test conditions for that DTC (listed on the facing page of the Diagnostic Trouble Code table) and refer to conditions for setting the DTC. The DTC should not re-set after the repair has been made.