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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Select IMS on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does each range selected match the scan tool IMS display? If so, see INTERMITTENT CONDITIONS within appropriate ENGINE PERFORMANCE article. If not, go to next step.
    NOTE: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
  3. Select IMS A/B/C/P on the scan tool. Place the gearshift lever in each transmission range: P, R, N, D4, D3, D2 and D1. Does the IMS A/B/C/P display HI/HI/HI/HI for each range? If so, go to step  13 . If not go to next step.
  4. Turn OFF the ignition. Disconnect the AT inline 20-pin connector, additional DTCs may set. Turn ON the ignition, with the engine OFF. Select IMS A/B/C/P on the scan tool. Do the scan tool IMS A/B/C/P signals all indicate HI? If so, go to next step. If not, go to step  9 .
  5. Turn OFF the ignition. Install the 20 Pin Jumper Harness (J 44152) on the engine side of the AT inline 20-pin connector. Turn ON the ignition, with the engine OFF. Using the DMM and the GM Terminal Test Kit (J 35616-A), measure the voltage at terminal "F" of the 20 pin jumper harness. Refer to Automatic Transmission Inline 20-pin Connector End View. Measure the voltage at terminal "G" of the 20 pin jumper harness. Measure the voltage at terminal "H" of the 20 pin jumper harness. Measure the voltage at terminal "J" of the 20 pin jumper harness. Does the voltage measure ignition voltage at all four terminals? If so, go to next step. If not, go to step  10 .
  6. Connect a fused jumper wire from terminal "F" of the 20 pin jumper harness signal "A" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "A" circuit (CKT 771) is grounded, do any other signal circuits indicate LOW? If so, go to step  11 . If not, go to next step.
  7. Connect a fused jumper wire from terminal "G" of the 20 pin jumper harness signal "B" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "B" circuit (CKT 772) is grounded, do any other signal circuits indicate LOW? If so, go to step  11 . If not, go to next step.
  8. Connect a fused jumper wire from terminal "H" of the 20 pin jumper harness signal "C" circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. When signal "C" circuit (CKT 773) is grounded, do any other signal circuits indicate LOW? If so, go to step  11 . If not, go to step  12 .
  9. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate HI for a short to ground between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step  18 . If not, go to step  17 .
  10. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate ignition voltage for an open between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step  18 . If not, go to step  17 .
  11. Test the affected signal circuits of the IMS for a shorted together condition between the PCM connector C1 or C2 and the AT inline 20-pin connector. Did you find and correct the condition? If so, go to step  18 . If not, go to step  17 .
  12. Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS for an open or shorted condition between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to step  15 . If not, go to step  16 .
  13. Test the ground circuit (CKT 451) of the IMS for an open between the AT inline 20-pin connector and the ground connection to the chassis. Did you find and correct the condition? If so, go to step  18 . If not, go to next step.
  14. Test the ground circuit (CKT 1050) of the IMS for an open between the AT inline 20-pin connector and the IMS. Did you find the condition? If so, go to next step. If not, go to step  16 .
  15. Replace the automatic transmission wiring harness assembly. See TRANSAXLE INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. When replacement is complete, go to step  18 .
  16. Replace the lever assembly-manual shaft detent with internal mode switch. See PARKING SYSTEM COMPONENTS  under REMOVAL & INSTALLATION. When replacement is complete, go to step  18 .
  17. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. When replacement is complete, go to next step.
  18. Perform the following procedure in order to verify the repair:
    • Select DTC.
    • Select Clear Info.
    • Start and idle the engine in Park for 10 seconds.
    • Observe IMS on the scan tool. The IMS must indicate a valid range for 5 seconds.
    • Select Specific DTC.
    • Enter DTC P1825.

    Has the test run and passed? If so, go to next step. If not, go to step  2 .

  19. With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? If so, go to appropriate ENGINE PERFORMANCE article. If not, the system is OK.
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