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Home >> Toyota >> 2003 >> Matrix Base, FWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 110 (Engine Control System Self Diagnostics (2UZ-FE)) >> Diagnostic Tests >> DTC P0571: Stoplight Switch Signal Circuit >> Diagnosis & Repair
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Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
  1. If Toyota hand-held tester is available, go to next step. If Toyota hand-held tester is not available, go to step  6.
  2. Check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, repair as necessary and retest system. See appropriate EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT.
  3. Connect hand-held tester to Data Link Connector (DLC3) at driver's side of instrument panel. See Figure. Turn ignition on and then turn hand-held tester on.
  4. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Backprobing, measure voltage between ECM 32-pin connector E6 terminal No. 1 (-) and ECM 35-pin connector E7 terminal No. 12 (+) (Red/Blue wire). This is the ST1- terminal on ECM. Monitor STP signal and ST1- voltage on hand-held tester while depressing and releasing brake pedal. STP signal should indicate ON with brake pedal depressed and OFF with brake pedal released. The ST1- voltage should be below 1.5 volts when pedal is depressed and 7.5-14 volts when pedal is released. If STP signal and ST1- voltage are not as specified, go to next step. If STP signal and ST1- voltage are as specified, problem is intermittent. Check for defective connections or intermittent problem in wiring harness between stoplight switch and ECM, and for intermittent problem with stoplight switch.
  5. Disconnect ECM 35-pin connector E7. See Figure. Check continuity between stop light switch 4-pin connector terminal No. 1 and ECM 35-pin connector E7 terminal No. 19. Then, check continuity between stop light switch 4-pin connector terminal No. 4 and ECM 35-pin connector E7 terminal No. 12. Continuity should exist. Check for no continuity between ground and stop light switch 4-pin connector terminal No. 1 and No. 4. If continuity is as specified, replace ECM. If continuity is not as specified, repair or replace wires and/or connectors as necessary.
  6. Check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, repair as necessary and retest system. See appropriate EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT.
  7. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Backprobing, measure voltage between ECM 32-pin connector E6 terminal No. 1 (-) and ECM 35-pin connector E7 terminal No. 12 (+) (Red/Blue wire). This is the ST1- terminal on ECM. The ST1- voltage should be below 1.5 volts when pedal is depressed and 7.5-14 volts when pedal is released. Then, backprobing, measure voltage between ECM 32-pin connector E6 terminal No. 1 (-) and ECM 35-pin connector E7 terminal No. 19 (+) (Green/Yellow wire). This is the STP terminal on ECM. The STP voltage should be below 1.5 volts when pedal is released and 7.5-14 volts when pedal is depressed. If STP and ST1- voltage are not as specified, go to next step. If STP and ST1- voltage are as specified, problem is intermittent. Check for defective connections or intermittent problem in wiring harness between stoplight switch and ECM, and for intermittent problem with stoplight switch.
  8. Disconnect ECM 35-pin connector E7. See Figure. Check continuity between stop light switch 4-pin connector terminal No. 1 and ECM 35-pin connector E7 terminal No. 19. Then, check continuity between stop light switch 4-pin connector terminal No. 4 and ECM 35-pin connector E7 terminal No. 12. Continuity should exist. Check for no continuity between ground and stop light switch 4-pin connector terminal No. 1 and No. 4. If continuity is as specified, replace ECM. If continuity is not as specified, repair or replace wires and/or connectors as necessary.
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