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Home >> Lexus >> 2002 >> ES 300 >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1520: Stoplight Switch Signal Circuit >> Diagnosis & Repair

Diagnosis & Repair

  1. Check stoplight operation. If stoplights do not operate properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT. If stoplights operate properly, go to next step.
  2. Connect hand-held tester to DLC No. 3. See Figure. Turn ignition on and push hand-held tester main switch on. Read STP signal on hand-held tester. With brake pedal depressed, STP signal should be on. With brake pedal released, STP signal should be off. If signal is not as specified, go to next step. If signal is as specified, problem is intermittent. Check component and ECM connections.
  3. Check for short in wiring between ECM and stoplight switch. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
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