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Home >> Mitsubishi >> 2002 >> Montero XLS >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - R4A51, V4A51 & V5A51 >> Diagnostic Tests >> DTC 23 (P0720): Output Shaft Speed Sensor 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. Using scan tool, monitor output shaft speed sensor. Start the engine. Drive vehicle at a constant speed of 31 MPH in 3rd gear (4-speed) or 4th gear (5-speed). On 3.0L models, the scan tool display should indicate 1500-1800 RPM. On 3.5L models, the scan tool display should indicate 1400-1700 RPM. Turn ignition off. Is the output shaft speed sensor operating properly? If so, malfunction is intermittent. If not, go to next step.
  2. Check the ground voltage at PCM harness connector by backprobing. Do not disconnect harness connector. Turn ignition on. Measure voltage between PCM harness connector terminal No. 57 and ground. Voltage should be 0.5 volt or less. Turn ignition off. Is the voltage as specified? If so, go to step  5 . If not, go to next step.
  3. Check PCM harness connectors for damage. Are the PCM harness connectors in good condition? If so, go to next step. If not, repair or replace defective harness connector(s).
  4. Using scan tool, monitor output shaft speed sensor. Start the engine. Drive vehicle at a constant speed of 31 MPH in 3rd gear (4-speed) or 4th gear (5-speed). On 3.0L models, the scan tool display should indicate 1500-1800 RPM. On 3.5L models, the scan tool display should indicate 1400-1700 RPM. Turn ignition off. Is the sensor 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.
  5. Check the sensor output voltage at PCM harness connector by backprobing. Do not disconnect harness connector. Disconnect output shaft speed sensor harness connector. Turn ignition on. Measure the voltage between PCM harness connector terminal No. 104 and ground. Voltage should be 4.5-4.9 volts. Turn ignition off. Is the voltage as specified? If so, go to step  8 . If not, go to next step.
  6. Check all output shaft speed sensor 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 a short to ground between PCM harness connector terminal No. 104 and output shaft speed sensor harness connector terminal No. 2. Is the wire harness in good condition? If so, go to step  4 . If not, repair wire harness as necessary.
  8. Using the oscilloscope, check the waveform at PCM harness connectors by backprobing. Do not disconnect harness connectors. Connect an oscilloscope probe to PCM harness connector terminals No. 57 and 104. Start the engine and run at constant speed of 31 MPH in 3rd gear (4-speed) or 4th gear (5-speed). Check the waveform. The waveform should show a pattern similar to the illustration. See Figure . The waveform voltage value should be 0.8-4.8 volts. The output waveform should not contain electrical noise. Turn ignition off. Is the waveform normal? If so, go to next step. If not, go to step  10 .
  9. Check PCM harness connectors for damage. Are the harness connectors in good condition? If so, go to step  4 . If not, repair or replace the defective harness connector(s).
  10. Check PCM and output shaft speed sensor 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).
  11. Disconnect output shaft speed sensor harness connector. Measure resistance at the harness side between output shaft speed sensor harness connector terminal No. 1 and ground. Resistance should be less than 2 ohms. Is the resistance as specified? If so, go to step  13 . If not, go to next step.
  12. Check all output shaft speed sensor circuit harness connectors for damage. Are the harness connectors in good condition? If so, repair open or damage in wire harness between output shaft speed sensor harness connector terminal No. 1 and PCM harness connector terminal No. 57. If not, repair or replace the defective harness connector(s).
  13. Check the sensor output voltage at output shaft speed sensor harness connector. Disconnect output shaft speed sensor harness connector. Turn ignition on. Measure voltage between output shaft speed sensor harness connector terminal No. 2 and ground. Voltage should be 4.5-4.9 volts. Turn ignition off. Is the voltage as specified? If so, go to step  15 . If not, go to next step.
  14. Check all output shaft speed sensor circuit harness connectors for damage. Are the harness connectors in good condition? If so, repair open wire harness between output shaft speed sensor harness connector terminal No. 2 and PCM harness connector terminal No. 104. If not, repair or replace the defective harness connector(s).
  15. Check the power supply voltage at output shaft speed sensor harness connector. Disconnect output shaft speed sensor harness connector and measure at the harness side. Turn ignition on. Measure the voltage between output shaft speed sensor harness connector terminal No. 3 and ground. Battery voltage should exist. Turn ignition off. Is the voltage as specified? If so, go to step  17 . If not, go to next step.
  16. Check all output shaft speed sensor circuit harness connectors for damage. Are the harness connectors in good condition? If so, repair open or short to ground in wire harness between output shaft speed sensor harness connector terminal No. 3 and junction block harness connector connector. If not, repair or replace the defective harness connector(s).
  17. Replace the output shaft speed sensor. Test drive the vehicle. Check for DTCs. Is DTC 23 present? If so, go to next step. If not, inspection is complete.
  18. Check output shaft speed sensor 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).
  19. Check wire harness for damage between output shaft speed sensor harness connector terminal No. 2 and PCM harness connector terminal No. 104. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
  20. Check wire harness for damage between output shaft speed sensor harness connector terminal No. 1 and PCM harness connector terminal No. 57. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
  21. Check wire harness for damage between output shaft speed sensor harness connector terminal No. 3 and junction block harness connector. Is the wire harness in good condition? If so, go to next step. If not, repair wire harness as necessary.
  22. Replace the output shaft (4-speed) or the direct planetary carrier (5-speed). See appropriate OVERHAUL article. Test drive the vehicle. Check for DTCs. Is DTC 23 present? If so, DTC may have set due to RFI, possibly caused by cellular phone activity, after market components installed on the vehicle, etc. If not, inspection is complete.
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