Input E.7.1 - VCC Brake Switch

ECM Input E.7.1:

DFI Transmission Circuit:

DESCRIPTION:

The VCC brake switch is normally closed and opens when the brake pedal is depressed. The VCC brake switch serves three functions: the brake switch supplies power to the VCC solenoid and the cruise vacuum valve and a brake ON/OFF indication to the ECM.

The VCC brake switch receives 12 volts from the 5 AMP cruise fuse #18 on CKT 239 and sends the 12 volt signal to the ECM and cruise control on CKT 420 and to the VCC solenoid on CKT 420. When the brake is depressed, the switch opens and CKT 420 voltage is read by the ECM as 0 volts.

On the diagnostic display, "HI" is a closed switch (not braking) while "LO" is an open switch (brake pedal depressed).

The ECM uses VCC brake input to determine braking status for VCC apply and release, as well as a test condition for many codes.

NOTES ON FAULT TREE:

1. At key on, not braking, should have 12 volts on both sides of VCC brake switch. Test light to ground should light if either pin on brake switch connector is backprobed.

2. Light on one side means that brake switch is open as if the brake pedal were depressed.

3. No light indicates open between fuse and the brake switch.

4. Checking for proper brake switch operation. If switch test doesn't pass and there is power at the switch, fault is switch, circuit, or ECM.

NOTE ON INTERMITTENTS:

a. Check brake switch for proper adjustment.
b. Check for intermittent open between fuse and brake switch and ECM.
c. If cruise fuse blows intermittently, check for short to ground from fuse to brake switch, VCC, cruise, or ECM.