PCM controls TCC operation based on coolant temperature, throttle position, transaxle range switch position, vehicle speed sensor and brake pedal switch. System also includes several other switches and sensors which are used for engine control. These components are covered in the ENGINE PERFORMANCE section.
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, DTCs 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 factory recommended Tech 1 scan tool or aftermarket 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 codes are repaired. For additional information on diagnosing and repairing engine related PCM trouble codes, see the ENGINE PERFORMANCE section.
NOTE:To test electronic control of transaxle solenoid without using self-diagnostics or if self-diagnostics does not function, go to appropriate COMPONENT TESTS under ELECTRONIC TESTING. After repairs are made, DTCs should be erased from computer memory. See CLEARING TROUBLE CODES under ELECTRONIC SELF-DIAGNOSTICS.
NOTE:Trouble codes will be recorded at various operating times. Some codes require operation of affected sensor or switch for 5 seconds; others may require operation for 5 minutes or longer at normal operating temperature, road speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.
NOTE:Stored DTCs may be retrieved from PCM memory using a factory recommended Tech 1 scan tool or aftermarket scan tool. DTCs CANNOT be retrieved by grounding 16-pin Data Link Connector (DLC). Plugging scan tool into DLC, located under instrument panel, enables user to read DTCs and check voltages in system on serial data line.
Scan tools may also furnish information on status of output devices (solenoids and relays). However, status parameters are only an indication that output signals have been sent to devices by control module; they do not indicate if devices have responded properly to signal. Check for proper response at output device using a voltmeter or test light.
If trouble codes are not present, this is not necessarily an indication a problem does not exist. Driveability related problems with codes displayed occur about 20 percent of the time, while driveability problems without codes occur about 80 percent of the time. Sensors that are out of specification WILL NOT set a trouble code but WILL cause driveability problems. Using scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harness and connections (key on, engine off) while observing scan tool.
Thursday, July 29th, 2010 AT 3:32 AM