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Home >> Mitsubishi >> 2002 >> Montero XLS >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - R4A51, V4A51 & V5A51 >> Diagnostic Tests >> DTC 26: Stoplight Switch Circuit - Open/Shorted >> Diagnostic Procedure

Diagnostic Procedure

CAUTION: To prevent damage to scan tool, always turn the ignition off before connecting or disconnecting scan tool.
  1. Check the brake pedal height. See appropriate DISC & DRUM article in BRAKES. Is the height adjusted properly? If so, go to next step. If not, adjust brake pedal height as necessary.
  2. Using scan tool, monitor stoplight switch. Turn ignition on. When the brake pedal is depressed, the scan tool display should indicate ON. When the brake pedal is not depressed, the scan tool display should indicate OFF. Turn ignition off. Is the switch operating properly? If so, malfunction is intermittent. If not, go to next step.
  3. Check the stoplight switch. See STOPLIGHT SWITCH  under COMPONENT TESTS. Is the switch okay? If so, go to next step. If not, replace the stoplight switch.
  4. Check stoplight switch harness connector for damage. Is the harness connector in good condition? If so, go to next step. If not, repair or replace defective harness connector.
  5. Check the stoplight switch output voltage at PCM harness connector by backprobing. Do not disconnect harness connector. Measure the voltage between PCM harness connector terminal No. 123 and ground. When the brake pedal is depressed, battery voltage should exist. When the brake pedal is not depressed, voltage should be less than one volt. Is the voltage as specified? If so, go to step  8 . If not, go to next step.
  6. Check all brake switch circuit harness connectors for damage. Are the harness connectors in good condition? If so, go to next step. If not, repair or replace the defective harness connector(s).
  7. Check wire harness for damage between stoplight switch harness connector terminal No. 1 and PCM harness connector terminal No. 123. Is the wire harness in good condition? If so, go to step  9 . If not, repair wire harness as necessary.
  8. Check PCM harness connectors for damage. Are the harness connectors in good condition? If so, go to next step. If not, repair or replace defective harness connector(s).
  9. Using scan tool, monitor stoplight switch. Turn ignition on. When the brake pedal is depressed, the scan tool display should indicate ON. When the brake pedal is not depressed, the scan tool display should indicate OFF. Turn ignition off. Is the stoplight switch operating properly? If so, malfunction is intermittent. If not, possible faulty PCM exists. Replace the PCM if necessary. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION.
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