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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 59 (Automatic Transmission Diagnosis - 4L80-E) >> Symptom Tests >> Range Selector Display Inoperative Or Displays Incorrect Range >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: See TRANSMISSION RANGE SWITCH LOGIC  table for valid combinations of switch signal circuits "A", "B", "C" and Parity. In the table, HI indicates an ignition voltage signal, and LOW indicates a zero voltage signal.
  1. Install a scan tool. Turn ignition on, engine off. Select TR SW. on the scan tool. With the scan tool, observe the TR SW. display while selecting each transmission range. Does each selected transmission range match the scan tool TR SW. display? If so, go to next step. If not, go step  3.
  2. Observe the Instrument Panel Cluster (IPC) gear range display while selecting each transmission range. Does each selected transmission range match the IPC display? If so, see DIAGNOSTIC AIDS . If not, go to step  16.
  3. With the scan tool, observe the TR SW. A/B/C/P display. Does the scan tool TR SW. A/B/C/P parameter indicate HI for all range signal states? If so, go to step  13. If not, go to next step.
  4. Turn ignition off. Disconnect the TR switch 4-way connector. Turn ignition on, engine off. Does the scan tool TR SW. A/B/C/P parameter indicate HI for all range signal states? If so, go to next step. If not, go to step  10.
  5. Using a DVOM and the Connector Test Adapter Kit (J-35616-A), measure the voltage from TR switch 4-way connector terminal "A" to ground. Measure the voltage from TR switch 4-way connector terminal "B" to ground. Measure the voltage from TR switch 4-way connector terminal "C" to ground. Measure the voltage from TR switch 4-way connector terminal "D" to ground. Does the voltage measure 10-12 volts at all 4 terminals? If so, go to next step. If not, go to step  11.
  6. Connect a fused jumper wire from TR switch 4-way connector terminal "A" (signal circuit "A") to ground while monitoring the scan tool TR SW. A/B/C/P parameter. When signal circuit "A" (771) is grounded, do any other signal circuits indicate LOW? If so, go to step  12. If not, go to next step.
  7. Connect a fused jumper wire from TR switch 4-way connector terminal "D" (signal circuit "B") to ground while monitoring the scan tool TR SW. A/B/C/P parameter. When signal circuit "B" (772) is grounded, do any other signal circuits indicate LOW? If so, go to step  12. If not, go to next step.
  8. Connect a fused jumper wire from TR switch 4-way connector terminal "B" (signal circuit "C") to ground while monitoring the scan tool TR SW. A/B/C/P parameter. When signal circuit "C" (773) is grounded, do any other signal circuits indicate LOW? If so, go to step  12. If not, go to next step.
  9. Connect a fused jumper wire from TR switch 4-way connector terminal "C" (signal circuit "P") to ground while monitoring the scan tool TR SW. A/B/C/P parameter. When signal circuit "P" (776) is grounded, do any other signal circuits indicate LOW? If so, go to step  12. If not, go to step  13.
  10. Test the TR switch signal circuits (771, 772, 773 and 776) that did not indicate HI for a short to ground. Did you find and correct the condition? If so, go to step  17. If not, go to step  15.
  11. Test the TR switch signal circuits (771, 772, 773 and 776) that did not indicate proper voltage for an open. Did you find and correct the condition? If so, go to step  17. If not, go to step  15.
  12. Test the affected TR switch signal circuits for a shorted together condition. Did you find and correct the condition? If so, go to step  17. If not, go to step  15.
  13. Test the TR switch ground circuit (451) for an open. Did you find and correct the condition? If so, go to step  17. If not, go to next step.
  14. Replace the TR switch (this switch is part of the park/neutral position switch). See PARK/NEUTRAL POSITION SWITCH  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17.
  15. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17.
  16. Replace the IPC. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Did you complete the replacement? If so, go to next step. If not, go to step  2.
  17. Turn ignition on, engine off. With the scan tool, observe the TR SW. display while selecting each transmission range. Does each selected transmission range match the scan tool TR SW. display? If so, system is okay. If not, go to step  2.
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