The Viscous Converter Clutch (VCC) brake switch is normally closed and opens when brake pedal is depressed. The VCC brake switch supplies power to VCC solenoid. To do so, brake switch receives 12 volts from a 15-amp "IGN 1" fuse on circuit No. 39, and sends the 12-volt signal to ECM and VCC solenoid on circuit No. 420. When brake is depressed, switch opens and circuit No. 420 voltage is read by ECM as zero volts.

A "HI" on diagnostic display, indicates that switch is closed (no braking) while a "LO" display indicates an open switch (brake pedal depressed). ECM uses VCC brake input to determine braking status for VCC apply and release, as well as a test condition for many codes.

NOTE: Test numbers refer to test numbers on diagnostic chart.

With key on and no braking, circuit 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.
Light on one side means that brake switch is open as if brake pedal were depressed.
Light on circuit No. 420 with pedal depressed means that brake switch never opens.
Unplug and plug ECM connector and ensure that it is latched.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

ECM Input Code EI71 - VCC Brake Switch Circuit: Notes

Use the Manual With the Right Hardware

When to See a Mechanic