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Computerized Engine Controls: Notes

NOTE: Refer to appropriate illustration for engine control component locations. See Fig 1-Fig 14 .

Computerized engine control system consists of a Powertrain Control Module (PCM), various input sensors, controlled devices and actuators (outputs) and related wiring which links system together. PCM monitors engine and vehicle functions while controlling (outputs) engine fuel control, Ignition Control (IC), automatic transaxle shift functions, cruise control enable, generator, Evaporative Emission Purge (EVAP), Exhaust Gas Recirculation (EGR), A/C clutch operation and cooling fan operation.

PCM performs On-Board Diagnostics-II (OBD-II) diagnostic tests of emission related systems. OBD-II diagnostics ensure emission systems operate correctly and have not degraded to a point where vehicle emissions exceed local emission standards.

In the event of an input or output failure, PCM will memorize and store information as a Diagnostic Trouble Code (DTC). DTCs can be used by technician to diagnose various driveability and emission related problems. DTCs are accessed through On-Board Diagnostics-II Data Link Connector (OBD-II DLC) with use of an OBD-II compatible scan tool. OBD-II DLC is located under instrument panel, accessible from driver's side. See Fig 3 or Fig 13

PCM incorporates a fail-safe (limp-in) mode. If a fault occurs during vehicle operation, PCM will substitute a predetermined value and/or signal for continued operation. Driving performance will be affected, but vehicle may still be driven. When PCM detects a system fault, Malfunction Indicator Light (MIL) will flash or illuminate steadily to notify driver of a developing problem. For location of MIL, see Fig 2 or Fig 13 .

Fig 1: Locating Engine Control Components (Metro - 1 Of 4)
G00012620Courtesy of GENERAL MOTORS CORP.
Fig 2: Locating Engine Control Components (Metro - 2 Of 4)
G00012621Courtesy of GENERAL MOTORS CORP.
Fig 3: Locating Engine Control Components (Metro - 3 Of 4)
G00012622Courtesy of GENERAL MOTORS CORP.
Fig 4: Locating Engine Control Components (Metro - 4 Of 4)
G00012623Courtesy of GENERAL MOTORS CORP.
Fig 5: Locating Engine Control Components (Prizm - 1 Of 10)
G00012624Courtesy of GENERAL MOTORS CORP.
Fig 6: Locating Engine Control Components (Prizm - 2 Of 10)
G00012625Courtesy of GENERAL MOTORS CORP.
Fig 7: Locating Engine Control Components (Prizm - 3 Of 10)
G00012626Courtesy of GENERAL MOTORS CORP.
Fig 8: Locating Engine Control Components (Prizm - 4 Of 10)
G00012627Courtesy of GENERAL MOTORS CORP.
Fig 9: Locating Engine Control Components (Prizm - 5 Of 10)
G00012628Courtesy of GENERAL MOTORS CORP.
Fig 10: Locating Engine Control Components (Prizm - 6 Of 10)
G00012629Courtesy of GENERAL MOTORS CORP.
Fig 11: Locating Engine Control Components (Prizm - 7 Of 10)
G00012630Courtesy of GENERAL MOTORS CORP.
Fig 12: Locating Engine Control Components (Prizm - 8 Of 10)
G00012631Courtesy of GENERAL MOTORS CORP.
Fig 13: Locating Engine Control Components (Prizm - 9 Of 10)
G00012632Courtesy of GENERAL MOTORS CORP.
Fig 14: Locating Engine Control Components (Prizm - 10 Of 10)
G00012633Courtesy of GENERAL MOTORS CORP.
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