Circuit Description
The green VLT LED remains illuminated when the ignition is ON. The VLT LED flashes when system voltage is 9-11 volts or greater than 17 volts. The VLT LED turns OFF when voltage to the electronic brake control module (EBCM) is less than 9 volts.
Conditions for Running the Diagnostic Fault
The ignition is ON.
Conditions for Setting the Diagnostic Fault
The EBCM detects low or high system voltage.
Action Taken When the Diagnostic Fault Sets
| • | The ABS indicator turns ON. |
| • | The ABS is disabled. |
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:
Conditions for Clearing the Diagnostic Fault
Repair the condition responsible for setting the diagnostic fault.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The green VLT LED flashes if the system voltage is 9-11 volts or greater than 17 volts.
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This step tests for adequate power to the EBCM. Voltage of 9-11 volts may cause the green VLT LED to flash.
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This step tests for adequate EBCM ground.
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Total lack of voltage on all of the ignition 3 voltage circuits may be due to a malfunction in the ABS relay circuitry.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Air Antilock Brake System Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Turn ON the ignition. Does the green VLT LED remain ON steady? | Go to Diagnostic Aids | Go to Step 3 |
Ensure the charging system is operating normally. Refer to Charging System Test and Symptoms - Engine Electrical . Did you find and correct the condition? | Go to Step 17 | Go to Step 4 | |
Does the test lamp illuminate when each ignition 3 voltage circuit is probed? | Go to Step 6 | Go to Step 5 | |
5 | Test the ignition 3 voltage circuits that did not illuminate the test lamp for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 7 |
Use a test lamp connected to battery positive voltage in order to probe all 3 of the ground circuits at the EBCM harness connector, one at a time. Does the test lamp illuminate when each ground circuit is probed? | Go to Step 13 | Go to Step 12 | |
Does the test lamp illuminate? | Go to Step 8 | Go to Step 10 | |
8 | At the harness connector of the ABS relay, connect a test lamp between the ignition 3 voltage circuit , which supplies voltage to the ABS relay coil, and a good ground. Does the test lamp illuminate? | Go to Step 9 | Go to Step 11 |
9 | Connect a test lamp between battery positive voltage and the ground circuit of the ABS relay coil. Does the test lamp illuminate? | Go to Step 15 | Go to Step 12 |
10 | Repair the open in the battery positive voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 17 | -- |
11 | Repair the open in the ignition 3 voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 17 | -- |
12 | Repair the open in the ground circuits that did not illuminate the test lamp. Refer to Wiring Repairs . Did you complete the repairs? | Go to Step 17 | -- |
13 | Inspect for poor connections at the harness connectors of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 14 |
14 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | -- |
15 | Inspect for poor connections at the harness connectors of the ABS relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 17 | Go to Step 16 |
16 | Replace the ABS relay. Did you complete the replacement? | Go to Step 17 | -- |
17 |
Does the green VLT LED remain ON steady? | System OK | Go to Step 3 |
