The diagnostic system check is an organized approach to identifying a problem created by an antilock brake system (ABS) malfunction. It must be the starting point for any ABS complaint diagnosis because it directs the service technician to the next logical step in diagnosing the complaint.
Diagnostic Aids
Perform the following steps in order when servicing the ABS/EBD system. Failure to do so may result in the loss of important diagnostic data and may lead to difficulties and time-consuming diagnosis procedures.
- Perform the tests of the following table.
- Perform a road test if directed by the table.
- Clear the diagnostic trouble codes (DTCs) after all system malfunctions have been corrected.
| • | Test drive the vehicle while using the snapshot feature of the scan tool. |
| • | Perform normal acceleration, stopping, and turning maneuvers. |
| • | If this does not reproduce the malfunction, perform an ABS stop on a low friction surface such as gravel. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Is the scan tool receiving data from the electronic brake control module (EBCM)? | -- | Go to Step 2 | Go to Step 6 |
2 | Observe the display. Are there any current diagnostic trouble codes (DTCs) displayed? | -- | Refer to the applicable DTC table | Go to Step 3 |
3 |
Does the indicator light for 4 seconds and then turn OFF? | -- | Go to Step 5 | Go to Step 4 |
4 | Observe the ABS indicator. Did the ABS indicator turn ON and stay ON? | -- | Go to ABS Indicator Always On | |
5 |
Does the indicator light for 4 seconds and then turn OFF? | -- | Go to Step 12 | Go to Brake Warning Indicator Inoperative in Hydraulic Brakes |
6 |
Does the voltage measure within the specified range on each terminal? | 11-14 V | Go to Step 7 | |
7 |
Is the resistance equal to the specified value? | 0 ohms | Go to Step 9 | Go to Step 8 |
8 | Repair the open in the circuit BK and BK/WH that failed. Did you complete the repair? | -- | System OK | -- |
9 | Use a DVM to measure the resistance between terminal 11 of the EBCM harness connector and terminal 12 of the data link connector (DLC). Does the resistance measure less than the specified value? | 2 ohms | Go to Step 10 | Go to Step 11 |
10 | Replace the ABS unit assembly. Did you complete the replacement? | -- | System OK | -- |
11 | Repair the open or high resistance in circuit D-BU between terminal 11 of the EBCM harness connector and terminal 12 of the DLC jack. Did you complete the repair? | -- | Go to Step 1 | -- |
12 | Perform the road test described in the Diagnostic Process. Are any DTCs set? | -- | Go to the table for the DTC | -- |
