Circuit Description
The Brake Lamp Switch is normally open switch. When the brake lamp switch is closed, the TAC module senses ignition voltage on the brake switch signal circuit. The PCM compares this signal to the signal received from the other brake switches. If these switches do not agree this DTC will set.
Conditions for Running the DTC
| • | The engine speed is greater than 700 RPM. |
| • | The engine operates longer than 2 second. |
| • | The wheel speed must be greater than 30 MPH in order to enable the diagnostic. The diagnostic will disable when the wheel speed is below 10 MPH. |
| • | The vehicle speed is decreasing at a rate greater than 10.4 MPH over a one second period. |
Conditions for Setting the DTC
| • | The PCM senses this switch is not toggling as compared with other brake switch inputs. |
| • | The condition is present for 20 accel/decel cycles. |
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear Info function. |
Diagnostic Aids
Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing/replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
In order to adjust the Brake Lamp Switch perform the following:
- With the brake pedal depressed, insert the Brake Lamp Switch into the retainer until the switch body seats in the retainer. You can hear clicks as you push the threaded portion of the switch through the retainer.
- Slowly pull the brake pedal fully rearward against the stop until you can no longer hear the clicks.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the fault is present.
-
This step verifies that the Brake switch is functioning properly.
-
Check for a short to ground between the fuse and the Stop Lamp switch and between the Stop Lamp switch and the TAC module.
-
This DTC will not report a pass. The scan tool status for this DTC will never report a pass. The scan tool will only display when the diagnostic fails. The repair is not complete if the scan tool indicates that the diagnostic ran and failed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 | With a scan tool, observe the TAC Brake Switch parameter. Does the scan tool indicate Released? | -- | ||
3 | Depress the brake pedal approximately half-way. Does the scan tool indicate Applied? | -- | Go to Diagnostic Aids | |
4 | Test the adjustment of the Brake switch. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes. Did you find and correct the condition? | -- | ||
5 | Inspect the condition of the fuse. Is the fuse open? | -- | ||
6 |
Does the voltage at or near the specified voltage? | B+ | ||
7 |
Does the DMM indicate continuity? | -- | ||
8 |
Does the test lamp illuminate? | -- | ||
9 | Probe the brake switch signal circuit at the brake switch connector using a test lamp that is connected to B+. Does the test lamp illuminate? | -- | ||
10 | Probe the brake switch signal circuit at the TAC module connector using a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | ||
Does the DMM switch from open to continuity while toggling the switch? | -- | |||
12 | Repair the open in the brake switch feed circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
13 | Repair the open in the brake switch signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
14 | Repair the short to ground in the brake switch feed circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
15 | Repair the short to ground in the brake switch signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
16 | Repair the short to voltage in the brake switch signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
17 | Replace the Brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | -- | -- | |
18 | Inspect for faulty connections at brake switch and TAC module. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | ||
19 | Replace the TAC module. Refer to Accelerator Pedal Replacement Did you complete the replacement? | -- | -- | |
Does the DTC reset? | -- | |||
21 | Does the scan tool indicate any DTCs set that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
