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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 73 (Automatic Transmission Diagnosis - 4L80-E (Gasoline)) >> 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 Cab & Chassis Sierra and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: See TRANSMISSION RANGE SWITCH LOGIC  table under DECSCIPTION & OPERATION for valid combinations of switch signal circuits "A", "B", "C" and Parity. On the table, "HI" indicates an ignition voltage signal. "LOW" indicates a zero voltage signal.
  1. Review ELECTRONIC COMPONENTS  under DESCRIPTION & OPERATION. Did you review the electronic component description and perform the necessary inspections? If so, go to next step. If not, see ELECTRONIC COMPONENTS  under DESCRIPTION & OPERATION.
  2. Place the transmission in Park. Turn the ignition on. Move gearshift lever into each gear position. Observe and record the transmission range indication displayed in each gear position. Does the PRNDL indicate the correct gear in each position? If so, see DIAGNOSTIC AIDS  . If not, go to next step.
  3. Are all of the PRNDL indicators inoperative? If so, go to next step. If not, go to step  6 .
  4. Test the off/run/crank voltage circuit for an open, high resistance or a short to ground. Did you find and correct the condition? If so, go to step  17 . If not, go to next step.
  5. Test the PNP switch ground circuit for an open or high resistance. Did you find and correct the condition? If so, go to step  17 . If not, go to next step.
  6. Disconnect PNP switch connector. Turn the ignition on. Measure the voltage of the transmission range switch "A" signal circuit. Does the voltage measure 10-12 volts? If so, go to next step. If not, go to step  11 .
  7. Measure the voltage of the TR switch "P" signal circuit. Does the voltage measure 10-12 volts? If so, go to next step. If not, go to step  12 .
  8. Measure the voltage of the TR switch "B" signal circuit. Does the voltage measure 10-12 volts? If so, go to next step. If not, go to step  13 .
  9. Measure the voltage of the TR switch "C" signal circuit. Does the voltage measure near battery voltage? If so, go to next step. If not, go to step  14 .
  10. Disconnect the PNP switch connector. Turn the ignition on. Using fused jumper wires, ground the appropriate TR switch circuits. See TRANSMISSION RANGE SWITCH LOGIC  table under DECSCIPTION & OPERATION. Do the inoperative PRNDL indicators illuminate? If so, go to step  16 . If not, go to step  15 .
  11. Repair the open, high resistance or short to ground in the TR switch "A" signal circuit. Is the repair complete? If so, go to step  17 . If not, go to step  2 .
  12. Repair the open, high resistance or short to ground in the TR switch "P" signal circuit. Is the repair complete? If so, go to step  17 . If not, go to step  2 .
  13. Repair the open, high resistance or short to ground in the TR switch "B" signal circuit. Is the repair complete? If so, go to step  17 . If not, go to step  2 .
  14. Repair the open, high resistance or short to ground in the TR switch "C" signal circuit. Is the repair complete? If so, go to step  17 . If not, go to step  2 .
  15. Replace the instrument panel cluster. Is the repair complete? If so, go to step  17 . If not, go to step  2 .
  16. Adjust or replace the PNP switch. See PARK/NEUTRAL POSITION SWITCH  under REMOVAL & INSTALLATION. Is the repair complete? If so, go to next step. If not, go to step  2 .
  17. Operate the system to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step  2 .
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