With Scan Tool
ACCESSING AND READING ABS DIAGNOSTIC TROUBLE CODESFig. 92 TECH 1 Scan Tool Operation (Part 1 Of 3).:
Fig. 92 TECH 1 Scan Tool Operation (Part 2 Of 3).:
Fig. 92 TECH 1 Scan Tool Operation (Part 3 Of 3).:
This system contains sophisticated on-board diagnostics that can only be accessed with a bi-directional scan tool. To properly diagnose the anti-lock brake system, a GM TECH 1 bi-directional scan tool or suitable equivalent is necessary. The scan tool can be used to identify system faults as specifically as possible, including whether or not the fault is intermittent. The scan tool can also be used to monitor the input and output signals of the ABS Module, manually control system components and perform automated functional tests. Using the scan tool allows for accurate fault confirmation and repair verification.
1. Connect GM TECH 1 or equivalent scan tool to Data Link Connector (DLC), then read all current and history diagnostic trouble codes. Refer to Fig. 92 for scan tool operation. Be sure to note which diagnostic trouble codes are current failures. Do not clear diagnostic trouble codes unless directed to do so.
2. Read "CODE HISTORY" data, note diagnostic trouble codes stored and their frequency of failure. Ensure to note the last diagnostic trouble code entered and the conditions present when the failure occurred. This last diagnostic trouble code should be the starting point for diagnosis and repair.
3. Before beginning service on this system, perform the following preliminary inspection:
a. Check master cylinder for proper brake fluid level.
b. Inspect hydraulic modulator for any leaks or wiring damage.
c. Inspect brakes at all four wheels to ensure no drag exists and that brakes are operating normally.
d. Check wheel bearings for any excessive wear or damage.
e. Inspect wheel speed sensors for correct air gap, solid sensor attachment, damaged toothed ring or damaged wiring. Refer to System Service. Wheel Speed Sensor
f. Check CV joint for proper operation and alignment.
4. When plugged into the DLC connector, the TECH 1 scan tool can display ABS data, display and clear ABS diagnostic trouble codes, control ABS components or perform diagnostic testing for intermittent conditions. The TECH 1 uses five different test modes to aid in diagnosis. Use the following TECH 1 diagnostic modes when servicing this system:
a. MODE F0: DATA LIST: In this mode, the scan tool continuously monitors wheel speed data, brake switch status and other inputs and outputs.
b. MODE F1: CODE HISTORY: In this mode, diagnostic trouble code history data is displayed. This includes how many ignition cycles since the diagnostic trouble code occurred and other ABS information.
c. MODE F2: DIAGNOSTIC TROUBLE CODES: In this mode both current and history diagnostic trouble codes can be displayed or cleared.
d. MODE F3: ABS SNAPSHOT: In this mode, scan tool captures ABS data before and after a fault occurrence or a forced manual trigger.
e. MODE F4: ABS TESTS: In this mode, scan tool performs hydraulic modulator functional tests to assist in problem isolation during troubleshooting.
5. Refer to Diagnostic Trouble Code Interpretation for further information regarding specific diagnostic trouble codes. Accessing and Reading ABS Diagnostic Trouble Codes