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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Toyota Land Cruiser, 2002 Lexus LX 470, 2001 Toyota Land Cruiser, and 2001 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: If not using Lexus/Toyota scan tool, skip step  2.
  1. Inspect operation of stop lights. Repair as needed. If switch is suspect, see STOP LIGHT SWITCH  under COMPONENT TESTS. If circuit is suspect, diagnose and repair as necessary. See WIRING DIAGRAMS .
  2. Connect scan tool to DLC3. See Figure. Turn the ignition to the ON position. Read STP signal while depressing and releasing brake pedal. Ensure signal reads STP ... ON when pedal is pressed and STP ... OFF when released. If signal is okay, check for an intermittent condition. If signal is not okay, go to step  4.
  3. Check voltage between terminal STP of ECM and ground while depressing and releasing brake pedal. See WIRING DIAGRAMS . Readings should be between 7.5-14 volts when brake pedal is depressed and below 1.5 volts when released. If voltage is okay, check for an intermittent condition. If voltage is not okay, go to next step.
  4. Check circuit between stop light switch and ECM. If problem was found, replace wiring harness and connector. If circuit is okay, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
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