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Test 56: Input And/Or Output Speed Sensor Error

NOTE: Large transmission in-line harness connector is 12-way (12-pin) on 1997 models and 14-way (14-pin) on 1998 models.
  1. If DTC 58 is also set, perform TEST 58: SENSOR GROUND ERROR . If DTC 58 is not set, go to next step.
  2. Raise and support vehicle. Start engine. Place gearshift lever in "OD" position. Release brakes and allow wheels to rotate. Using scan tool, monitor input and output RPM. If both RPM values are greater than zero, go to next step. If both RPM values are not as specified, go to step 12).
  3. Apply brakes. Place gearshift lever in "P" position. Maintain engine speed at 1000 RPM. Record input and output RPM on scan tool display. If output speed is about 2500 RPM when input speed is 1000 RPM, perform TEST 58: SENSOR GROUND ERROR . If input and output RPM is not as specified, go to next step.
  4. Turn ignition off. Disconnect Transmission Range (TR) sensor and TCM harness connectors. Measure resistance between speed sensor ground circuit and input speed sensor signal circuit at TCM harness connector. If resistance is 300-1200 ohms, go to step 6). If resistance is not as specified, go to next step.
  5. Disconnect large transmission in-line harness connector. Measure resistance between speed sensor ground circuit and input speed sensor signal circuit at transmission side of large transmission in-line harness connector. If resistance is 300-1200 ohms, repair open in speed sensor ground circuit between TCM and large transmission in-line harness connector. If resistance is not as specified, repair open in speed sensor ground circuit between TCM and input/output speed sensor harness connectors.
  6. Reconnect large transmission in-line harness connector. Turn ignition on. Measure voltage between ground and speed sensor ground circuit at TCM harness connector. Place gearshift lever in each gear position and record voltage at each position. If voltage is greater than one volt in any gear position, go to next step. If voltage is not as specified, go to step 8).
  7. Disconnect large transmission in-line harness connector. Measure voltage between ground and speed sensor ground circuit at harness side of large transmission in-line harness connector. If voltage is greater than one volt, repair speed sensor ground circuit for a short to power between TCM and large transmission in-line harness connector. If voltage is not as specified, repair speed sensor ground circuit for a short to power between large transmission in-line harness connector and input/output speed sensor harness connectors.
  8. Turn ignition off. Reconnect TR sensor and large transmission in-line harness connectors. Measure voltage between ground and speed sensor ground circuit at TCM harness connector. Place gearshift lever in each gear position and record voltage at each position. If voltage is greater than one volt in any gear position, replace TR sensor and TCM. If voltage is not as specified, go to next step.
  9. Turn ignition off. Disconnect input and output speed sensor harness connectors and inspect for damage. Repair as necessary. If harness connectors are okay, go to next step.
  10. Reconnect TCM and both speed sensor harness connectors. Start engine. Apply brakes and place gearshift lever in "OD" position. Using scan tool, monitor input and output speeds. If both input and output speeds read zero RPM, conditions necessary to set DTC 56 are not present at this time. If both input and output speeds do not read zero RPM, go to next step.
  11. Turn ignition off. Measure resistance between chassis ground and TCM ground circuit at TCM harness connector. If resistance is less than 5 ohms, inspect and repair secondary ignition wiring (misrouted) as necessary. If resistance is not as specified, repair open in TCM ground circuit.
  12. If output speed sensor RPM is zero, go to step 21). If output speed sensor RPM is not zero, go to next step.
  13. Disconnect TCM harness connector. Inspect TCM harness connector terminal No. 13 (speed sensor ground circuit) and terminal No. 52 (input speed sensor signal circuit). Repair as necessary. Measure resistance between ground and input speed sensor signal circuit at TCM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, go to step 16).
  14. Disconnect input speed sensor harness connector. Measure resistance between ground and input speed sensor signal circuit at input speed sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, replace input speed sensor.
  15. Disconnect large transmission in-line harness connector. Measure resistance between ground and input speed sensor signal circuit at transmission side of large transmission in-line harness connector. If resistance is less than 5 ohms, repair input speed sensor signal circuit for a short to ground between large transmission in-line harness connector and input speed sensor harness connector. If resistance is not as specified, repair input speed sensor signal for a short to ground between TCM harness connector and large transmission in-line harness connector.
  16. Measure resistance between input speed sensor signal circuit and speed sensor ground circuit at TCM harness connector. If resistance is 300-1200 ohms, replace TCM. If resistance is not as specified, go to next step.
  17. Disconnect large transmission in-line harness connector. Measure resistance of input speed sensor signal circuit between TCM harness connector and large transmission in-line harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, repair open in input speed sensor signal circuit.
  18. Disconnect input speed sensor harness connector. Measure resistance of input speed sensor signal circuit between input speed sensor harness connector and transmission side of large transmission in-line harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, repair open in input speed sensor signal circuit between input speed sensor harness connector and large transmission in-line harness connector.
  19. Measure resistance of speed sensor ground circuit between large transmission in-line harness connector and input speed sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, repair open in speed sensor ground circuit.
  20. 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, replace input speed sensor. If resistance is not as specified, repair open in speed sensor ground circuit between large transmission in-line harness connector and TCM harness connector.
  21. If input speed sensor RPM is zero, go to step 25). If input speed sensor RPM is not zero, go to next step.
  22. Turn ignition off. Disconnect TCM harness connector. Inspect TCM harness connector terminal No. 13 (speed sensor ground circuit) and terminal No. 14 (output speed sensor signal circuit). Repair as necessary. Measure resistance between ground and output speed sensor signal circuit at TCM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, go to step 29).
  23. Disconnect output speed sensor harness connector. Measure resistance between ground and output speed sensor signal circuit at output speed sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, replace output speed sensor.
  24. Disconnect large transmission in-line harness connector. Measure resistance between ground and output speed sensor signal circuit at transmission side of large transmission in-line harness connector. If resistance is less than 5 ohms, repair output speed sensor signal circuit for a short to ground between large transmission in-line harness connector and output speed sensor harness connector. If resistance is not as specified, repair output speed sensor signal for a short to ground between TCM and large transmission in-line harness connector.
  25. Inspect input and output speed sensor harness connections. Repair as necessary. If connections are okay, go to next step.
  26. Disconnect Transmission Range (TR) sensor and TCM harness connectors. Turn ignition on. Measure voltage between ground and speed sensor ground circuit at TCM harness connector. Place gearshift lever in each gear position. Record voltage in each position. If voltage is greater than one volt in any gear position, go to step 28). If voltage is not as specified, go to next step.
  27. Disconnect TR sensor harness connector. Turn ignition on. Measure voltage between ground and speed sensor ground circuit at TCM harness connector. Place gearshift lever in each gear position. Record voltage in each position. If voltage is greater than one volt in any gear position, replace TR sensor and TCM. If voltage is not as specified, replace TCM.
  28. Disconnect large transmission in-line harness connector. Measure voltage between ground and speed sensor ground circuit at harness side of large transmission in-line harness connector. If voltage is greater than one volt, repair speed sensor ground circuit for a short to power between large transmission in-line harness connector and TCM harness connector. If voltage is not as specified, repair speed sensor ground circuit for a short to power between large transmission in-line harness connector and output speed sensor harness connector.
  29. Measure resistance between output speed sensor signal circuit and speed sensor ground circuit at TCM harness connector. If resistance is 300-1200 ohms, replace TCM. If resistance is not as specified, go to next step.
  30. Disconnect large transmission in-line harness connector. Measure resistance of output speed sensor 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 output speed sensor signal circuit between large transmission in-line harness connector and TCM harness connector.
  31. Disconnect output speed sensor harness connector. Measure resistance of output speed sensor signal circuit between transmission side of large transmission in-line harness connector and output speed sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, repair open in output speed sensor signal circuit between large transmission in-line harness connector and output speed sensor harness connector.
  32. Measure resistance of speed sensor ground circuit between transmission side of large transmission in-line harness connector and output speed sensor harness connector. If resistance is less than 5 ohms, replace output speed sensor. If resistance is not as specified, repair open in speed sensor ground circuit between large transmission in-line harness connector and output speed sensor harness connector.
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