Circuit Description
When the brake pedal is depressed, the stop light switch sends a signal to the engine control module (ECM). When the ECM receives this signal, it cancels the cruise control. The fail-safe function operates to enable normal driving even if there is a malfunction in the stop light signal circuit. The cancellation condition occurs when voltage is applied to ECM connector A50 terminal 36. When the brake is applied, voltage is normally applied to terminal 36 of the ECM through the STOP fuse and the stop light switch, and the ECM turns the cruise control off.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0571 Brake Switch Circuit 1
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
Voltage at terminals 35 and 36 of the ECM are less than 1 volt for 0.5 second or more.
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs with the fault active. |
| • | The ECM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
Diagnostic Aids
A scan tool should indicate the state of the stop light switch.
An intermittent malfunction may be caused by a fault in the stop light electrical circuit. Inspect the wiring harness and the components for any of the following conditions:
| • | Any backed-out terminals |
| • | Any improper mating of terminals |
| • | Any broken electrical connector locks |
| • | Any improperly formed or damaged terminals |
| • | Any faulty terminal-to-wire connections |
| • | Any physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Any corrosion of the electrical connections, the splices, or the terminals |
Repair any electrical circuit faults that were found. Refer to Wiring Repairs .
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Cruise Control Schematics Connector End View Reference: Component Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Is the voltage measured within specified value? | 11-14 Volts | Go to Step 3 | Go to Step 6 |
3 |
Are the resistance values within the specified values? | Not Pushed: 1 and 2 = Below 1 Ohm Not Pushed: 3 and 4 = Below 10 Kohm or higher Pushed: 1 and 2 = Below 10 Kohm or higher Pushed: 3 and 4 = Below 1 Ohm | Go to Step 4 | Go to Step 7 |
4 |
Are the voltages within the specified values? | Pedal Depressed: Terminal 36 to body ground = 11 - 14 Volts Pedal Depressed: Terminal 35 to body ground = Below 1 Volt Pedal Released: Terminal 35 to body ground = 11 - 14 Volts Pedal Released: Terminal 35 to body ground = Below 1 Volt | Go to Step 5 | Go to Step 8 |
5 | Repair or replace harness or stop light switch connector. Refer to Wiring Repairs and Connector Repairs . Did you complete the repair or replacement? | Pedal Depressed: No Continuity Pedal Released: Continuity | Go to Step 9 | -- |
6 | Replace the stop light switch. Refer to Stop Lamp Switch Replacement . Did you complete the replacement? | Pedal Depressed: Continuity Pedal Released: No Continuity | Go to Step 9 | -- |
7 | Repair or replace harness or ECM connector. Refer to Wiring Repairs and Connector Repairs . Did you complete the repair or replacement? | -- | Go to Step 9 | -- |
8 | Replace the ECM. Refer to Control Module References for ECM replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
