Reading Diagnostic Trouble Codes

Data Link Connector (DLC):

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 Transmission Control (TC) diagnostic trouble codes when the diagnostic terminal of the DLC connector is grounded.


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.

NOTE: 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.