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Home >> Mitsubishi >> 2001 >> Montero XLS >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - R4A51, V4A51 & V5A51 >> Diagnostic Tests >> DTC 29: Vehicle Speed Sensor Circuit - Open/Shorted >> Diagnostic Procedure (Montero)

Diagnostic Procedure (Montero)

CAUTION: To prevent damage to scan tool, always turn the ignition off before connecting or disconnecting scan tool.
  1. Check the speedometer. Is the speedometer operating properly? If so, go to next step. If not, see appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
  2. Using scan tool, monitor VSS. Ensure speedometer and scan tool display match when driving vehicle at 25 MPH. Is the VSS operating properly? If so, malfunction is intermittent. If not, go to next step.
  3. Using the oscilloscope, check the waveform at PCM harness connector by backprobing. Do not disconnect harness connector. Connect an oscilloscope probe to PCM harness connector terminal No. 80. Start the engine and run vehicle. Check the waveform. The waveform should show a pattern similar to the illustration. See Figure . Is the waveform normal? If so, go to step  5 . If not, go to next step.
  4. Check all VSS circuit harness connectors for damage. Are the harness connectors in good condition? If so, repair open or damage in wire harness between PCM harness connector terminal No. 80 and joint connector terminal No. 32. If not, repair or replace the defective harness connector(s).
  5. 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).
  6. Using scan tool, monitor VSS. Ensure speedometer and scan tool display match when driving vehicle at 25 MPH. Is the VSS 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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