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Home >> Cadillac >> 1998 >> Eldorado Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1527 - Transaxle Range/Pressure Switch Comparison >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Ensure P/N position switch and shift cable/lever are adjusted properly. Set parking brake and block drive wheels. Start engine. Move shift lever through each range and observe TFP switch (pressure) and transmission range on scan tool. If scan tool display matches each other for the range that is selected, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not match each other for the range selected, go to next step.
  3. If TFP switch matches each range selected, go to next step. If TFP switch does not match each range selected, go to step 17).
  4. Turn ignition on. Using scan tool, observe Trans Range A/B/C/P display. If all the modes display ON (High), go to step 13). If modes does not display ON (High), go to next step.
  5. If any of the modes (A/B/C/P) stay ON (high) or OFF (low) all the time regardless of selector position, go to next step. If modes does not stay ON or OFF all the time, go to step 15).
  6. If the mode(s) that did not change would always display ON (high), go to step 9). If not, go to next step.
  7. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector. Disconnect transaxle range switch. Using DVOM, check resistance between ground on the circuit(s) that were always OFF (low).
    • Mode A is circuit No. 771
    • Mode B is circuit No. 772
    • Mode C is circuit No. 773
    • Mode P is circuit No. 776

    If resistance on tested circuit(s) is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, go to step 11).

  8. Repair short to ground in circuit(s) that have low or no resistance to ground.
  9. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector. Disconnect transaxle range switch. Using DVOM, check resistance between transaxle range switch connector and PCM harness connector C1 terminals on circuit(s) that were always ON (high).
    • Mode A is circuit No. 771
    • Mode B is circuit No. 772
    • Mode C is circuit No. 773
    • Mode P is circuit No. 776

    If resistance on tested circuit(s) is greater than 5 ohms, go to next step. If resistance is not greater than 5 ohms, go to step 12).

  10. Repair open in circuit(s) that have high or infinite resistance..
  11. Reconnect PCM harness connector (leave transaxle range switch disconnected). Turn ignition on. Check Trans Range A/B/C/P display. If all modes indicate ON (high), go to step 16). If all modes does not indicate ON (high), go to step 23).
  12. Reconnect PCM harness connector (leave transaxle range switch disconnected). Turn ignition on. Check Trans Range A/B/C/P display. Using jumper wire, jumper transaxle range switch connector circuit that was always ON (high) to ground. If display changes from ON to OFF when circuit is jumpered, go to step 15). If display does not change from ON to OFF when circuit is jumpered, go to step 23).
  13. Turn ignition off. Disconnect transaxle range switch ground connector. Check resistance to ground in circuit No. 451. If resistance is 5 ohms or less, go to step 15). If resistance is not 5 ohms or less, go to next step.
  14. Repair open or high resistance in circuit No. 451.
  15. Check for 2 or more mode circuits shorted together. Repair as necessary. If circuit is okay, check terminal contact at transaxle range switch. If terminal contact is okay, go to next step.
  16. Replace transaxle range switch.
  17. If DTC P1810 is also present, diagnose using DTC P1810 test. If DTC P1810 is not present, go to next step.
  18. Start engine. Check if Trans Range (pressure) match in P, R, N and D4, but not in D1, D2 and D3. If pressure matches, go to step 20). If pressure does not match, go to next step.
  19. Replace transmission fluid pressure manual valve position switch assembly.
  20. Disconnect transaxle 20-pin harness connector. Shift through all gear ranges. If scan tool display ALWAYS indicate P/N, go to next step. If scan tool does not indicate P/N, go to step 22).
  21. Check transaxle range B input circuit between transaxle 20-pin harness connector and PCM for short to ground. Repair as necessary. If circuit is okay, go to step 23).
  22. Check for short to ground between transaxle 20-pin connector and transmission fluid pressure manual valve position switch or for a faulty fluid pressure manual valve position switch. Repair or replace as necessary.
  23. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
  24. Replace PCM. Program replacement PCM using required equipment.
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