Basic Strategies
Tool Required: TECH-1When servicing the ABS, the following steps should be followed in order. Failure to follow these steps may result in the loss of important diagnostic data and may lead to difficult and time-consuming diagnosis procedures:
1) Using the TECH-1, read all current and history Diagnostic Trouble Codes (DTCs). Be certain to note which DTCs are current malfunctions. DO NOT CLEAR DTCs unless directed to do so.
2) Using the TECH-1, read the DTC HISTORY data. Note the DTCs stored and their frequency of failure. Specifically, note the last failure that occurred and the conditions present when this failure occurred. This "last failure" is what brought the customer in for service, and should be the starting point for diagnosis and repair.
3) Perform a vehicle preliminary diagnosis inspection. This should include:
- Inspection of the master cylinder fluid reservoir for proper brake fluid level and for any signs of contamination.
- Inspection of the hydraulic modulator for any leaks or wiring damage.
- Inspection of brake components at all four wheels, Verify no drag exists. Also, verify proper brake apply operation.
- Inspection for worn or damaged wheel bearings that may allow a wheel to "wobble."
- Inspection of the wheel speed sensors and their wiring. Verify solid sensor attachment, undamaged sensor toothed ring and undamaged wiring, especially at vehicle attachment points.
- Verify proper wheel-side constant velocity joint alignment and operation.
- Verify tires meet legal tread depth requirements.
4) If no DTC, or mechanical component malfunctions are present, perform the "Modulator Test" later in this section using the TECH-1 to isolate the cause of the problem.
If the failure is intermittent and not reproducible, test drive the vehicle while using the automatic snapshot feature of the TECH-1. Perform normal acceleration, stopping and turning maneuvers. If this does not reproduce the malfunction, perform an ABS stop, on a low coefficient surface such as gravel, from approximately 48 to 80 km/h (30 to 50 mph) while triggering the snapshot mode on any ABS DTC. If the failure is still not reproducible, use the enhanced diagnostic information found in DTC HISTORY to determine whether or not this malfunction should be diagnosed further.
5) Once all system malfunctions have been corrected, clear the ABS DTCs.