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Using Available Diagnostic Information

Data Link Connector (DLC):






READING DIAGNOSTIC TROUBLE CODES
The provision for communicating with the PCM is the diagnostic link connector (DLC), known before as the ALDL connector. It is located under the instrument panel. It is used in the assembly plant to receive information in checking that the engine is operating properly before it leaves the plant.

The diagnostic trouble code(s) stored in the PCM's memory can be read either through a hand-held diagnostic scanner plugged in the DLC connector or by:
1. Counting the number of flashes of the malfunction indicator lamp (MIL) for PCM Engine Control (EC) diagnostic trouble codes, when the diagnostic terminal of the DLC connector is grounded OR
2. Counting the number of flashes of the LOW COOLANT/HOT lamp for PCM/ Transaxle Controller (TC) diagnostic trouble codes when the diagnostic terminal of the DLC connector is grounded.

NOTE: The codes for the ABS systems can only be read with a scan tool or other diagnostic equipment. When an ABS fault is detected, the ABS telltale is lit and the codes are stored in memory.

The DLC connector terminal B (diagnostic terminal) is the second terminal from the right of the DLC connector's top row. The terminal is most easily grounded by connecting it to terminal A (internal PCM ground), the terminal to the right of terminal B on the top row of the DLC connector.

Once terminals A and B have been connected, the ignition switch must be moved to the On position, with the engine not running. At this point, the malfunction indicator lamp (MIL) should flash DTC 12 three times consecutively. This would be the following flash sequence: Flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash. DTC 12 indicates that the PCM's diagnostic system is operating. If DTC 12 is not indicated, a problem is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart.

Following the output of DTC 12, the malfunction indicator lamp (MIL) will indicate a diagnostic trouble code three times if a diagnostic trouble code is present, or it will simply continue to output diagnostic trouble code 12. If more than one DTC has been stored in the PCM's memory, the diagnostic trouble codes will be displayed from the lowest to the highest, with the exception of DTC 11 which indicates transaxle diagnostic trouble codes. DTC 11 will always flash last followed by the HOT light, which will flash transaxle diagnostic trouble codes. Each diagnostic trouble code will be displayed three times.

Saturn also uses information flags. These information flags do not indicate a failure and will not turn on the malfunction indicator lamp (MIL). Information flags are used as diagnostic aids to the technician when hard diagnostic trouble codes or intermittent problems occur.

Engine information flags will not be flashed on the malfunction indicator lamp (MIL) and they can only be read with a Scan tool. Automatic Transaxle Information Flags will flash on the HOT light.

MALFUNCTION INDICATOR LAMP
The malfunction indicator lamp (MIL) "SERVICE ENGINE SOON" telltale lamp is in the instrument cluster and has the following functions:
^ It informs the driver that a problem has occurred and that the vehicle should be taken for service as soon as reasonably possible.
^ It displays diagnostic trouble codes stored by the PCM which help the technician diagnose system problems.
^ It indicates Open Loop or Closed Loop engine operation.

As a bulb and system check, the lamp will come On with the key On and the engine not running. When the engine is started, the lamp will turn Off. If the lamp remains On, the self-diagnostic system has detected a problem. If the problem goes away, the lamp will go out in most cases after 10 seconds, but a diagnostic trouble code will remain stored in the PCM.

When the lamp remains On while the engine is running, or when a malfunction is suspected due to a driveability problem an on-board diagnostic system check (OBD system check) must be performed. These checks will expose malfunctions which may not be detected if other diagnostics are performed prematurely. (Refer to the On Board Diagnostic System Check [OBD System Check]). Testing and Inspection


LOW COOLANT/HOT LAMP
When a transaxle malfunction is detected, the malfunction indicator lamp (MIL) telltale may illuminate. The telltale will illuminate for all diagnostic trouble codes, but will not illuminate for informations flags. If engine and transmission codes are present, a DTC 12 will flash which indicates the PCM diagnostics are functioning, followed by any engine diagnostic trouble codes that may be present. A DTC 11 will then flash indicating "Transaxle Diagnostic Trouble Codes". After DTC 11 is flashed three times, the low coolant/hot lamp will flash stored transaxle diagnostic trouble codes. If an information flag in the transaxle is stored along with the diagnostic trouble codes, they will also be flashed at this time. If only information flags are stored and a diagnostic check is complete, DTC 12 will flash followed by any engine diagnostic trouble codes. DTC 11 will not flash, but the low coolant/hot lamp will begin to flash transaxle flags. Automatic transaxle flags will not turn on the MIL lamp and are used as diagnostic aids.

If a faulty low coolant/hot telltale bulb or circuit is suspected, it can be checked with the Saturn Portable Diagnostic (Scan) (PDT) Tool by selecting the TCM menu. DTC 26 may also be logged if the low coolant/hot lamp circuit has a fault.

INTERMITTENT MALFUNCTION INDICATOR LAMP (MIL) TELLTALE LAMP
In the case of an intermittent problem, the malfunction indicator lamp (MIL) will light for 10 seconds and then will go out. However, the corresponding diagnostic trouble code or information flag will be stored in the memory of the PCM until removed.

An intermittent problem may or may not set a diagnostic trouble code or information flag. If it is an intermittent failure, a Diagnostic Trouble Code Chart is not used. Consult the Diagnostic Aids corresponding to the intermittent diagnostic trouble code or information flag. Also, refer to "Diagnosis by Symptoms". Testing and Inspection

A physical inspection of the applicable sub-system most often will resolve the problem.



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