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Test 74: Temperature Sensor Circuit

NOTE: Large transmission in-line harness connector is 12-way (12-way) on 1997 models and 14-way (14-way) on 1998 models.
  1. If DTCs 51-54 or 56-58 are also stored in TCM memory, perform appropriate test according to DTC set. If specified DTCs are not present, go to next step.
  2. Start engine. Using scan tool, select TRANSMISSION SENSORS. Read transmission temperature voltage signal. If voltage is greater than 4.94 volts, go to the next step. If voltage is not as specified, go to step 14).
  3. Turn ignition off. Disconnect large transmission in-line harness connector. Turn ignition on. Measure voltage between ground and transmission temperature signal circuit at harness side of large transmission in-line harness connector. If voltage is greater than 4.5 volts, go to step 6). If voltage is not as specified, go to next step.
  4. Turn ignition off. Disconnect TCM harness connector. Measure resistance of transmission temperature signal circuit between harness side of large transmission in-line harness connector and TCM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, repair open in transmission temperature signal circuit between large transmission in-line harness connector and TCM harness connector.
  5. Disconnect Transmission Range (TR) sensor harness connector. Measure resistance of transmission temperature signal circuit between transmission side of large transmission in-line harness connector and TR sensor harness connector. If resistance is less than 5 ohms, replace TCM. If resistance is not as specified, repair open in transmission temperature signal circuit between large transmission in-line harness connector and TR sensor harness connector.
  6. If voltage is greater than 5.5 volts, go to next step. If voltage is not as specified, go to step 9).
  7. Turn ignition off. Disconnect TCM harness connector. Turn ignition on. Connect a fused jumper wire between fused B+ (battery positive) circuit and transmission control relay output circuit at transmission control relay connector. Measure voltage between ground and transmission temperature signal circuit in TR sensor harness connector. If voltage is greater than 5.5 volts, go to next step. If voltage is not as specified, replace TCM.
  8. Ensure jumper wire is still connected. Disconnect large transmission in-line harness connector. Measure voltage between ground and transmission temperature signal circuit at harness side of large transmission in-line harness connector. If voltage is greater than 5.5 volts, repair transmission temperature signal circuit for a short to power between large transmission in-line harness connector and TR sensor harness connector. If resistance is not as specified, repair transmission temperature signal circuit for a short to power between large transmission in-line harness connector and TCM harness connector.
  9. Measure voltage between chassis ground and speed sensor ground circuit at TR sensor harness connector. If voltage is greater than one volt, go to step 13). If voltage is not as specified, go to next step.
  10. Connect a fused jumper wire between transmission temperature signal circuit and speed sensor ground circuit at TR sensor harness connector. Disconnect input and output speed sensor harness connectors. Using scan tool, select TRANSMISSION SENSORS. Read transmission temperature volts on scan tool display. If voltage is less than .5 volt, replace TR sensor. If voltage is not as specified, go to next step.
  11. Disconnect jumper wire from speed sensor ground circuit and connect to chassis ground. Read transmission temperature volts on scan tool display. If voltage is less than .5 volt, go to next step. If voltage is not as specified, replace TCM.
  12. Disconnect TCM and large transmission in-line harness connectors. Measure resistance of speed sensor ground circuit between harness side of large transmission in-line harness connector and TCM harness connector. If resistance is less than 5 ohms, repair open in speed sensor ground circuit between large transmission in-line harness connector and TCM harness connector. If resistance is not as specified, repair open in speed sensor ground circuit between large transmission in-line harness connector and TR sensor harness connector.
  13. Turn ignition off. Disconnect TCM harness connector. Connect a fused jumper wire between fused B+ (battery positive) circuit and transmission control relay output circuit in transmission control relay connector. Turn ignition on. Measure voltage between ground and speed sensor ground circuit at TR sensor harness connector. If voltage is greater than one volt, repair speed sensor ground circuit for a short to power. If voltage is not as specified, reconnect all harness connectors and components. Perform TEST 56: INPUT AND/OR OUTPUT SPEED SENSOR ERROR .
  14. If voltage is less than one volt, go to next step. If voltage is not as specified, go to step 18).
  15. Turn ignition off. Disconnect Transmission Range (TR) sensor harness connector. Turn ignition on. If transmission temperature voltage is greater than 4.5 volts, replace TR sensor. If voltage is not as specified, go to next step.
  16. Turn ignition off. Disconnect TCM harness connector. Measure resistance between ground and transmission temperature sensor signal circuit at TCM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, replace TCM.
  17. Disconnect large transmission in-line harness connector. Measure resistance between ground and transmission temperature sensor signal circuit at TCM harness connector. If resistance is less than 5 ohms, repair transmission temperature sensor signal circuit for a short to ground between large transmission in-line harness connector and TCM harness connector. If resistance is not as specified, repair transmission temperature sensor signal circuit for a short to ground between large transmission in-line harness connector and TR sensor harness connector.
  18. Disconnect Transmission Range (TR) sensor harness connector. Inspect connectors for damage or contamination. Repair as necessary. If connectors are okay, go to next step.
  19. Using scan tool, monitor and record transmission temperature voltage in all gear positions. If voltage is always .07-4.94 volts, go to next step. If voltage is not as specified, replace TR sensor.
  20. Using scan tool, monitor and record transmission temperature voltage while wiggling wiring harness between TR sensor and TCM. If voltage is always .07-4.94 volts, go to next step. If voltage is not as specified, repair intermittent open or short in wiring harness between TR sensor and TCM.
  21. Using a thermometer, measure and record temperature of transmission fluid. Start engine. Using scan tool, monitor and record transmission temperature voltage. Compare measured temperature and voltage. Ensure values fall on line in graph. See Fig 1. If transmission temperature voltage is correct compared to actual transmission fluid temperature, go to next step. If voltage is not correct, replace TR sensor.
  22. Turn ignition off. Disconnect TCM harness connector. Ensure transmission temperature is greater than 32°F (0°C). Measure resistance between transmission temperature signal circuit and sensor ground circuit at TCM harness connector. If resistance is between 150 ohms and 100 k/ohms, go to next step. If resistance is not as specified, replace TR sensor.
  23. Disconnect TR sensor harness connector. Inspect connectors for damage or corrosion. Repair as necessary. If connectors are okay, conditions necessary to set DTC 74 are not present at this time.
Fig 1: Transmission Temperature/Voltage Range Chart (Engine Running)
G98A01245Courtesy of CHRYSLER CORP.
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