Accessing and Reading Diagnostic Trouble Codes

Data Link Connector (DLC):

ANTILOCK TELLTALE LAMP
The telltale lamp in the instrument cluster has the following functions:
^ If the lamp comes on solid, it informs the driver that a problem has occurred and that the ABS system has been disabled. The vehicle should be taken for service as soon as possible.
^ The ABS telltale will only flash when a code 87 or 88 is set and the rear motors were found at the "not at home" position during the same ignition cycle. When this happens the yellow antilock telltale will come on solid then begin to flash. This is due to the inability of the controller to turn on the red brake telltale, in addition to the ABS telltale.
^ In addition to codes there are some failures which will not turn on the ABS telltale, but will store information related to a system malfunction. There are called information flags.


As a bulb and system check, the lamp will come ON with the key ON and the lamp will turn OFF after about three seconds. If the lamp remains ON or begins to flash, the self-diagnostic system has detected a problem. The lamp will remain on until the ignition is cycled off. When the ignition is cycled back on the ABS runs the self diagnostic test to see if the problem is still present. If the problem remains the light will come back on.


RED BRAKE TELLTALE LAMP
The red brake telltale lamp is located in the instrument panel cluster. It will light if any of the following conditions are met:
^ Low brake fluid level in master cylinder.
^ Parking brake switch is closed.
^ It is turned on by the antilock brake control module.


READING CODES
The provision for communicating with the ABS system is the data link connector (DLC) connector. The DLC is located under the instrument panel. The DLC is used to communicate with the PCM and ABS control modules.

The code(s) stored in the ABS control module memory can be read ONLY from the DLC with a scan tool or other diagnostic equipment.

When a ABS fault is detected, the ABS telltale is lit, and code(s) are placed in the General Information table (current codes). When the ignition is switched off, the current code(s) are moved to the Malfunction history table (past codes) and cleared from the General Information table.


CLEARING CODES
Current codes will be cleared when the ignition is turned off. Past codes (Malfunction History) will clear after 100 ignition cycles with no fault occurring. Both types of codes will be cleared when the clear codes selection is selected on the scan tool.



IMPORTANT: Disconnecting power to the ABS has no effect on stored codes in Malfunction history, but it will clear codes in general information.