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Home >> Mitsubishi >> 2002 >> Montero XLS >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - R4A51, V4A51 & V5A51 >> Diagnostic Tests >> DTC 16 (P0712): Transmission Fluid Temperature Sensor Circuit - Shorted >> Diagnostic Procedure

Diagnostic Procedure

CAUTION: To prevent damage to scan tool, always turn the ignition off before connecting or disconnecting scan tool.
  1. Install scan tool. Start engine. Using scan tool, monitor TFT sensor. When transmission fluid is cool, fluid temperature reading should be almost equal to the ambient temperature (atmospheric temperature) and when warm, fluid temperature reading should be 158-176°F (70-80°C). Turn ignition off. Is the sensor operating properly? If so, malfunction is intermittent. If not, go to next step.
  2. Check the TFT sensor output voltage at PCM harness connector by backprobing. Do not disconnect PCM harness connector. Turn ignition on. Measure voltage between PCM harness connector terminal No. 124 and ground. As transmission fluid temperature increases voltage decreases as follows:
    • When transmission fluid temperature is 68°F (20°C), voltage should be 3.8-4.0 volts.
    • When transmission fluid temperature is 104°F (40°C), voltage should be 3.2-3.4 volts.
    • When transmission fluid temperature is 176°F (80°C), voltage should be 1.7-1.9 volts.

    Turn ignition off. Is the voltage as specified? If so, go to next step. If not, go to step  5 .

  3. 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).
  4. Start engine. Using scan tool, monitor TFT sensor. When transmission fluid is cool, fluid temperature reading should be almost equal to the ambient temperature (atmospheric temperature) and when warm, fluid temperature reading should be 158-176°F (70-80°C). 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 PCM and transmission solenoid valve assembly 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).
  6. Check the TFT sensor at transmission solenoid valve assembly harness connector. Disconnect TFT sensor harness connector and measure at the sensor side. Measure the resistance between TFT sensor terminals No. 1 and 2. See FLUID TEMPERATURE SENSOR  under COMPONENT TESTS. Is the resistance as specified? If so, go to next step. If not, replace the TFT sensor. See appropriate SERVICING article.
  7. Check the power supply voltage at transmission solenoid valve assembly harness connector. Disconnect transmission solenoid valve assembly harness connector and measure at the harness side. Turn ignition on. Measure the voltage between transmission solenoid valve assembly harness connector terminal No. 1 and ground. Voltage should be 4.5-4.9 volts. Turn ignition off. Is the voltage as specified? If so, go to step  9 . If not, go to next step.
  8. Check all transmission fluid temperature circuit harness connectors between PCM and transmission for damage. Are the harness connectors in good condition? If so, repair short to ground in wire harness between transmission control solenoid valve assembly harness connector terminal No. 1 and PCM harness connector terminal No. 124.
  9. Check all transmission fluid temperature circuit harness connectors between PCM and transmission 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).
  10. Check wire harness for damage between transmission control solenoid valve assembly harness connector terminal No. 1 and PCM harness connector terminal No. 124. Is the wire harness in good condition? If so, repair damage to wire harness between transmission solenoid valve assembly harness connector terminal No. 2 and PCM harness connector terminal No. 57. If not, repair wire harness between transmission control solenoid valve assembly harness connector terminal No. 1 and PCM harness connector terminal No. 124.
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