Circuit Description
The Electronic Brake Control Module (EBCM) monitors the brake pedal position through the stoplamp switch. The stoplamp switch is closed when the brake pedal is pressed and the stop lamp switch opens when the brake pedal is released. When the stoplamp switch is closed, the EBCM terminal 5 receives a voltage signal from the stoplamp switch electrical connector terminal 1. The stoplamp switch receives power from the STOP fuse.
Conditions for Setting the DTC
| • | DTC B3449 identifies an open in the stoplamp switch circuit. |
| • | DTC B3449 can be set anytime. |
Action Taken When the DTC Sets
| • | A malfunction DTC stores. |
| • | The ABS warning indicator turns ON. |
| • | The ABS remains functional. |
Conditions for Clearing the DTC
The condition responsible for setting the DTC no longer exists. Use the Scan Tool Clear DTCs function.
Diagnostic Aids
Inspect the following items when diagnosing this part of the Antilock Brake System (ABS):
- The STOP fuse is open (possible short to ground in its circuitry).
- The stoplamp switch is out of adjustment.
- Faulty stoplamp switch (contacts open or closed at the time).
- An open circuit between the stoplamp switch and the EBCM.
- A short to voltage between the stoplamp switch and the EBCM.
An intermittent malfunction is most likely caused by following conditions:
| • | A poor connection |
| • | A rubbed through wire insulation |
| • | A wire that is broken inside the insulation |
Inspect the harness connectors for the following conditions:
| • | Backed-out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wiring connections, or physical damage to the wiring harness before component replacement: |
| • | Junction block electrical connectors |
| • | Stoplamp switch electrical connector. |
| • | EBCM electrical connector. |
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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The Diagnostic System Check must be the starting point for any ABS related diagnosis.
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Tests the stoplamp switch status of the Electronic Brake control Module (EBCM) through a scan tool.
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Tests the tail lamps for proper operation.
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Tests for a stoplamp switch that is out of adjustment or contacts closed all the time.
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Tests the power distribution to the stoplamp switch.
-
Test for an open or a high resistance in the power circuit to the stoplamp switch.
-
Tests for a faulty stoplamp switch.
-
Tests for an open or a high resistance in CKT 17.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 |
Does the scan tool display the stoplamp switch status ON with the brake pedal pressed and did the stoplamp switch status OFF with the brake pedal released? | -- | ||
3 | With the help of an assistant, press then release brake pedal while observing the rear brake lamps. Did the brake lamps turn ON with the brake pedal pressed and did the brake lamps turn OFF with the brake pedal released? | -- | ||
4 | Do the brake lamps stay ON at all times? | -- | ||
5 | Remove and inspect the STOP fuse. Is the STOP fuse open? | -- | ||
6 |
Is the voltage within the range specified in the value(s) column? | 0-1 V | ||
7 |
Is the resistance within the range specified in the Value(s) column for both readings? | Brake Pedal Released: OL (Infinite) Brake Pedal Pressed: 0-2 ohms | ||
8 |
Is the resistance within the range specified in the Value(s) column? | 0-2 ohms | ||
9 | Disconnect the stoplamp switch electrical connector. Are the brake lamps OFF? | -- | ||
10 | Repair the short to ground in CKT 17 or 140. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
11 | Repair the open in CKT 140 between the STOP fuse and the stoplamp switch. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
12 |
Is the repair complete? | -- | Go to Diagnostic System Check | -- |
13 |
Is the repair complete? | -- | Go to Diagnostic System Check | |
14 |
Is the repair complete? | -- | Go to Diagnostic System Check | -- |
15 | Repair the open in CKT 17 between the stoplamp switch harness connector terminal 1 and the EBCM harness connector terminal 5. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
16 | Repair the short to voltage in CKT 17. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
17 | A malfunction is not present at this time. Refer to Diagnostic Aids for additional information regarding this DTC. Is the action complete? | -- | Go to Diagnostic System Check | -- |
