Note. The CHECK ENGINE light is now referred to as Malfunction Indicator Light (MIL). The MIL is displayed in instrument cluster as CHECK ENGINE.
If no faults were found while performing BASIC TESTING , proceed with self-diagnostics. If no Diagnostic Trouble Codes (DTCs) are present after entering self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptoms.
SYSTEM DESCRIPTION
The PCM monitors engine operation. It also contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and compares them to On-Board Diagnostics Generation II (OBD-II) standards.
The goal of OBD-II regulation is to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emission control systems, and to improve diagnosis and repair when system failures occur.
The Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicles emissions could rise to greater than 1 1/2 times FTP standards.
DTCs may only be retrieved using an On-Board Diagnostic (OBD-II) scan tool. Use of Tech 2 scan tool is recommended. Other suitable aftermarket scan tools are available.
DESCRIPTION
The On-Board Diagnostic II (OBD-II) System Check is the starting point for any driveability complaint diagnosis. Before any DTC(s) are retrieved, perform a visual underhood inspection checking battery and grounds for clean and tight connections. Check for poor connections or damage to wiring harness and electrical connectors. Check for corroded terminals or corrosion build-up on any connection. Repair as necessary. The OBD-II system check is an organized approach to identifying problems created by an electronic engine control system malfunction.
Use of Tech 2 scan tool is required to perform ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK. To reprogram EEPROM or to program PCM after it has been replaced, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION section.
Note. To identify component terminals and wire colors, see appropriate wiring diagram in WIRING DIAGRAMS article.
See also:
• WIRING DIAGRAMS