Circuit Description
The electronic brake control module (EBCM) illuminates the service brake soon indicator by applying ground to the lamp.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step simulates the EBCM applying ground to the brake indicator signal circuit. If the fuse in the jumper wire opens when you perform this test, the telltale circuit board may be shorted or the brake indicator signal circuit may be shorted to voltage. Replace the fuse in the jumper wire and proceed to step 4.
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This step tests the brake indicator signal circuit for a short to voltage or an open by substituting the telltale circuit board with a test lamp. If the fuse in the jumper wire opens when you perform this test, the brake indicator signal circuit is shorted to voltage and the EBCM may be damaged.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Hydraulic Brake Schematics Important: Refer to the test description if performing steps 3 or 4 on this diagnostic table. | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Turn ON the ignition while observing the service brake soon indicator. Does the service brake soon indicator illuminate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
Does the service brake soon indicator illuminate? | Go to Step 6 | Go to Step 4 | |
Does the test lamp illuminate? | Go to Step 7 | Go to Step 5 | |
5 | Repair the open or short to voltage in the brake indicator signal circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 10 | -- |
6 | Inspect for poor connections at the harness connector 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 10 | Go to Step 9 |
7 | Inspect for poor connections at the harness connector of the telltale circuit board. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
8 | Replace the telltale circuit board. Refer to Telltale Circuit Board Replacement . Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the EBCM. Refer to Control Module References . Did you complete the replacement? | Go to Step 10 | -- |
10 | Turn ON the ignition while observing the service brake soon indicator. Does the service brake soon indicator illuminate for 3 seconds and then turn OFF? | System OK | Go to Step 3 |
