The diagnostic system check is an organized approach to identifying an Antilock Brake System (ABS) malfunction. The diagnostic system check must be the starting point for any ABS complaint diagnosis. The diagnostic system check directs the service technician to the next logical step in diagnosing the complaint. Refer to the appropriate table (below) for Gas, or Diesel engines.
Diagnostic serial data is transmitted/received by the EBCM through connector C1, terminal F (with Diesel), or terminal G (with Gas). The EBCM is supplied switched ignition voltage through connector C1, terminal A, and ground is provided through connector C1, terminal J.
Excessive resistance in the ground or power supply circuits will not allow communication with the EBCM. If communication with the EBCM is not possible, ensure that the ABS ground connection is good and that there is no excessive resistance in any of the power supply circuits.
The numbers below refer to the steps in the diagnostic table:
This step checks for normal ABS indicator lamp operation.
This step checks for ignition voltage at the EBCM.
This step checks for high resistance in the ground circuit.
This step checks for high resistance in the ignition voltage circuit.
This step checks for a short to ground in the ignition voltage circuit.
This step decides between ABS indicator lamp on always, or off always as the symptom.
This step decides between a short to ground in the 10-way EBCM harness/connector, or an internal EBCM fault.
Step | Action | Value(s) | Yes | No |
---|---|---|---|---|
1 |
Is data being received from the EBCM? | -- | ||
2 | Using the Scan Tool , check for any DTCs. Are any current or history DTCs displayed? | -- | Refer to Diagnostic Trouble Code (DTC) List | |
Did the ABS indicator lamp turn on for three seconds and then turn off? | -- | System is operating normally. Refer to Diagnostic Aids. | ||
Is the voltage measured within the specified range? | 10-15V | |||
Is the resistance measured within the specified range? | 0-2ohms | |||
6 |
Is the terminal contact or the connection poor? | -- | ||
7 | Replace the terminals or repair the poor connection. Is the repair complete? | -- | -- | |
8 | Reconnect the EBCM connectors and the battery cables. Are the EBCM connectors and the battery cables reconnected? | -- | Refer to Wiring Systems for serial data circuit diagnosis | -- |
Is the resistance measured within the specified range. | 0-2ohms | |||
Is the resistance measurement equal to the specified value? | OL | |||
Observe the ABS indicator lamp. Does the ABS indicator lamp stay on? | -- | Go to ABS Indicator Always On | ||
12 | Repair open or high resistance in CKT 150. Is the repair complete? | -- | -- | |
13 |
Is the repair complete? | -- | -- | |
14 |
Is the repair complete? | -- | -- | |
Inspect CKT 441 and the 10-way EBCM harness connector for physical damage which may result in a short to ground with the 10-way EBCM harness connector connected to the EBCM. Is there evidence of damage? | -- | |||
16 | Repair the terminals which are damaged. Is the repair complete? | -- | -- | |
17 |
Is the repair complete? | -- | -- |
The numbers below refer to the steps in the diagnostic table:
This step checks for normal ABS indicator lamp operation.
This step checks for ignition voltage at the EBCM.
This step checks for high resistance in the ground circuit.
This step checks for high resistance in the ignition voltage circuit.
This step checks for a short to ground in the ignition voltage circuit.
This step decides between ABS indicator lamp on always, or off always as the symptom.
This step decides between a short to ground in the 10-way EBCM harness/connector, or an internal EBCM fault.
Step | Action | Value(s) | Yes | No |
---|---|---|---|---|
1 |
Is data being received from the EBCM? | -- | ||
2 | Using the Scan Tool , check for any DTCs. Are any current or history DTCs displayed? | -- | Refer to Diagnostic Trouble Code (DTC) List | |
Did the ABS indicator lamp turn on for three seconds and then turn off? | -- | System is operating normally. Refer to Diagnostic Aids. | ||
Is the voltage measured within the specified range? | 10-15V | |||
Is the resistance measured within the specified range? | 0-2ohms | |||
6 |
Is the terminal contact or the connection poor? | -- | ||
7 | Replace the terminals or repair the poor connection. Is the repair complete? | -- | -- | |
8 | Reconnect the EBCM connectors and the battery cables. Are the EBCM connectors and the battery cables reconnected? | -- | Refer to Wiring Systems for serial data circuit diagnosis | -- |
Is the resistance measured within the specified range. | 0-2ohms | |||
Is the resistance measurement equal to the specified value? | OL | |||
Observe the ABS indicator lamp. Does the ABS indicator lamp stay on? | -- | Go to ABS Indicator Always On | ||
12 | Repair open or high resistance in CKT 150. Is the repair complete? | -- | -- | |
13 |
Is the repair complete? | -- | -- | |
14 |
Is the repair complete? | -- | -- | |
Inspect CKT 441 and the 10-way EBCM harness connector for physical damage which may result in a short to ground with the 10-way EBCM harness connector connected to the EBCM. Is there evidence of damage? | -- | |||
16 | Repair the terminals which are damaged. Is the repair complete? | -- | -- | |
17 |
Is the repair complete? | -- | -- |