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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 99 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0571: Brake Switch "A" Circuit >> Diagnosis & Repair

Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
  1. If not using hand-held tester, go to next step. If using hand-held tester, connect hand-held tester to DLC3. Turn ignition on and turn tester on. Select STOP LIGHT SW in DATA LIST and read value provided. With brake pedal depressed, tester should display ON. With brake pedal released, tester should display OFF. If okay, problem is cruise control related. See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT. If not okay, go to next step.
  2. Check if stop lights go on and off normally when the brake pedal is operated and released. Repair stop light circuit as necessary. If okay, go to next step.
  3. Remove the glove compartment door. Turn the ignition switch ON. Check the voltage between terminal STP and ST1- of the ECM connector and body ground. See Figure. See STOP LIGHT SWITCH VOLTAGE CHECK  table. If okay, check for intermittent problems or cruise control problem. See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT. If not okay, go to next step.
    STOP LIGHT SWITCH VOLTAGE CHECK

    Brake Pedal Position Terminal STP Terminal ST1-
    Depressed 10-14 Volts Below 1.0 Volt
    Released Below 1.0 Volt 10-14 Volts
  4. Check harness and connector between ECM STP terminal and stop light switch, and ECM ST1- terminal and stop light switch. Repair or replace harness or connector as necessary. If okay, check and replace ECM.
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