DTC P0719 Brake Switch Circuit Low Input 3.8L

Circuit Description

The brake switch indicates brake pedal status to the powertrain control module (PCM). The brake switch is a normally-closed switch that supplies battery voltage on circuit 420 to the PCM. Applying the brake pedal opens the switch, interrupting voltage to the PCM. When the brake pedal is released, the PCM receives a constant voltage signal. If the PCM receives a zero voltage signal at the brake switch input, and the torque converter clutch (TCC) is engaged, the PCM de-energizes the TCC solenoid valve. The PCM disregards the brake switch input for TCC scheduling if there is a brake switch circuit fault (Refer to Diagnostic Aids).

When the PCM detects an open brake switch circuit (0 volts, low input) during accelerations, then DTC P0719 sets. DTC P0719 is a type C DTC.

Conditions for Running the DTC

• No VSS assembly DTCs P0502 or P0503.
• The ignition is ON.

Conditions for Setting the DTC

The PCM detects an open brake switch or circuit (0 volts) for 15 minutes without changing for 2 seconds, and the following events occur eight times:

• The vehicle speed is less than 8 km/h (5 mph);
• then the vehicle speed is 8-32 km/h (5-20 mph) for 4 seconds;
• then the vehicle speed is greater than 32 km/h (20 mph) for 6 seconds.

Action Taken When the DTC Sets

• The PCM does not illuminate the malfunction indicator lamp (MIL).
• The PCM disregards the brake switch input for TCC scheduling.
• The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
• The PCM stores DTC P0719 in PCM history.

Conditions for Clearing the DTC

• A scan tool can clear the DTC.
• The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
• The PCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids

• Inspect the connectors at the PCM, the brake switch and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
• Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems.
• If the PCM detects a brake switch fault, then the brake switch input is disregarded for TCC scheduling. The PCM then uses throttle position and vehicle speed to determine TCC application and release. Use of these inputs may result in a noticeable harsh apply or abrupt release of the TCC.
• Ask about the customer's driving habits. Ask about unusual driving conditions (e.g. stop and go, expressway, etc.).
• Inspect the brake switch for proper mounting and operation.
• Inspect for ABS DTCs. A faulty ABS condition may contribute to setting DTC P0719.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

3. This step isolates the brake switch as a source for setting the DTC.

DTC P0719 Brake Switch Circuit Low Input (3.8L) Step	Action	Value(s)	Yes	No
1	Did you perform the Powertrain Diagnostic System Check?	--	Go to Step 2	Go to A Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
2	Install a Scan Tool . Turn ON the ignition, with the engine OFF. Important Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM. Record the DTC Failure Records. Clear the DTC. Select TCC Brake Switch on the Scan Tool . Disconnect the brake switch connector from the brake switch. Connect a test lamp from terminal C of the brake switch connector to ground. Does the test lamp illuminate?	--	Go to Step 3	Go to Step 4
3	Connect a fused jumper wire between terminal C and terminal D of the brake switch connector. Did the TCC Brake Switch status on the Scan Tool change from Open to Closed?	--	Go to Step 7	Go to Step 9
4	Inspect the ENG SEN fuse for an open. Refer to General Electrical Diagnosis Procedures in Wiring Systems. Is the fuse open?	--	Go to Step 5	Go to Step 8
5	Important The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics in Wiring Systems for complete circuit distribution. Test the power feed circuit (CKT 539) of the brake switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 11	Go to Step 6
6	Test input circuit (CKT 420) of the brake switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 11	Go to Step 10
7	Replace the brake switch. Refer to Stoplamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement?	--	Go to Step 11	--
8	Important The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics in Wiring Systems for complete circuit distribution. Test the power feed circuit (CKT 539) of the brake switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 11	--
9	Test the input circuit (CKT 420) of the brake switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 11	Go to Step 10
10	Replace the PCM. Refer to PCM Replacement/Programming in Engine Controls. Did you complete the replacement?	--	Go to Step 11	--
11	Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. Turn ON the ignition, with the engine OFF. Apply and release the brake pedal. Verify that the Scan Tool TCC Brake Switch status indicates Closed (12 volts) for 2 seconds. Select Specific DTC. Enter DTC P0719. Has the test run and passed?	--	System OK	Go to Step 1