GM Service Manual Online
For 1990-2009 cars only

Object Number: 62396  Size: MF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The brake switch indicates brake pedal status to the Powertrain Control Module (PCM). The Normally-Closed brake switch supplies battery voltage on circuit 420 to the PCM. Applying the brake pedal opens the switch, interrupting voltage to the PCM. Releasing the brake pedal resumes voltage to the PCM. When the PCM senses 0 volts at the brake switch input, the PCM de-energizes the Torque Converter Clutch Solenoid Valve.

When the PCM detects a closed brake switch (stuck OFF) during decelerations, then DTC P0724 sets. DTC P0724 is a type D DTC.

Conditions for Setting the DTC

DTC P0724 sets if the PCM detects a closed brake switch or circuit (12 volts) during vehicle deceleration and the following conditions occur six consecutive times:

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

Action Taken When the DTC Sets

    • The PCM does not illuminate the Malfunction Indicator Lamp (MIL).
    • DTC P0724 is stored in the PCM history.

Conditions for Clearing the DTC

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

Diagnostic Aids

    • Ask about the customer's driving habits. Ask about unusual traffic conditions and stop-and-go driving.
    • Inspect the brake switch for proper adjustment.
    • Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring for poor electrical connections at the brake switch connector and all other circuit connecting points. Look for the following conditions:
       - A bent terminal
       - A backed out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
       - Moisture intrusion
       - Corrosion
    • When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

Test Description

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

  1. Disconnecting the brake switch connector, and observing a status change, isolates the brake switch as the source of the DTC.

  2. If the brake switch is properly adjusted, then the brake switch must be replaced.

  3. This step inspects circuit 420 for a short to power, if the brake switch status on the scan tool did not change in Step 2.

  4. Replace the PCM only after you have completed the preceding diagnostic steps.

DTC P0724 Brake Switch Circuit -- High Input

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Install the Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.
  3. Important: Before clearing the DTC(s), use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM.

  4. Record the DTC Failure Records, then clear the DTC(s).
  5. Select Scan tool Brake Switch.
  6. Disconnect the brake switch connector.

Does the brake switch status change from Closed to Open?

--

Go to Step 3

Go to Step 4

3

Replace the brake switch.

Refer to Stoplamp Switch in the General Brakes Section.

Is the replacement complete?

--

Go to Step 6

--

4

Inspect circuit 420 for a short to power.

Refer to Troubleshooting Procedures in the Electrical Diagnosis Section.

Did you find and correct the condition?

--

Go to Step 6

Go to Step 5

5

Replace the PCM.

Refer to Powertrain Control Module/EEPROM Replacement/Programming .

Is the replacement complete?

--

Go to Step 6

--

6

In order to verify your repair, perform the following procedure:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
  4. • Turn the ignition switch to the RUN position.
    • Apply the brake pedal for at least 3 seconds.
  5. Select Specific DTC. Enter DTC P0724.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1