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Home >> Saturn >> 2002 >> LW200 Automatic >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - 4T40-E >> Description & Operation >> Electronic Control System

Electronic Control System

PCM constantly monitors all electrical circuits. If PCM detects circuit problems or sensors out of range, it will record a Diagnostic Trouble Code (DTC). If problem continues for a predetermined time, Malfunction Indicator Light (MIL) will light.

If MIL is on all the time, DTC(s) are currently being detected. If MIL is off, but PCM had detected a circuit or sensor problem, DTC(s) will be stored in computer memory.

Stored DTCs may be retrieved from PCM memory using a scan tool. DTCs CANNOT be retrieved by grounding 16-pin Data Link Connector (DLC).

NOTE: Faulty engine sensors and actuators may cause transaxle-related DTCs or driveability problems. Engine faults and related DTCs must be diagnosed and repaired before transaxle DTCs are repaired. For additional information on diagnosing and repairing engine-related DTCs, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.