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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 85 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0705: TRANSMISSION RANGE SWITCH CIRCUITDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedures

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition on, engine off. Using scan tool, monitor PNP switch. Move gearshift lever from "P" through "L" positions, checking each position. Is scan tool reading correct for each position? If so, problem is intermittent. See DIAGNOSTIC AIDS  . If not, go to next step.
  2. Is the reading always invalid? If so, go to step  12 . If not, go to next step.
  3. Move gearshift lever to "P" position. Is scan tool displaying PARK? If so, go to next step. If not, go to step  19 .
  4. Move gearshift lever to "R" position. Is scan tool displaying REVERSE? If so, go to next step. If not, go to step  27 .
  5. Move gearshift lever to "N" position. Is scan tool displaying NEUTRAL? If so, go to next step. If not, go to step  9 .
  6. Disconnect PNP switch 12-way harness connector. Jumper PNP switch 12-way connector terminal No. 7 to battery voltage. Using scan tool, monitor PNP switch A/B/C/P position "C". Does it read HI? If so, go to next step. If not, go to step  8 .
  7. Inspect PNP switch for loose terminal connections. Repair as necessary. If okay, replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  8. Inspect PNP switch position "C" (Gray wire) for open and loose terminal connections. Repair as necessary. If okay, replace TCM.
  9. Disconnect PNP switch 12-way harness connector. Using scan tool, monitor PNP switch A/B/C/P position "A". Does it read LOW? If so, go to next step. If not, go to step  11 .
  10. Replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  11. Inspect PNP switch position "A" (Tan/White wire) for a short to voltage. Repair as necessary. If okay, replace TCM.
  12. Disconnect PNP switch 12-way harness connector. Measure voltage between PNP switch 12-way harness connector terminal No. 11 (Pink wire) and ground. Is battery voltage measured? If so, go to next step. If not, go to step  14 .
  13. Inspect PNP switch for loose terminal connections. Repair as necessary. If okay, replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  14. Is BACKUP fuse (10-amp) blown? If so, go to next step. If not, go to step  16 .
  15. Inspect PNP switch ignition voltage circuit, PNP switch position "A", "P", "C" or "B" circuit and attached components for a short to ground. Repair as necessary.
  16. Measure voltage at ignition switch feed side of BACKUP fuse (10-amp). Is battery voltage present? If so, go to next step. If not, go to step  18 .
  17. Inspect ignition voltage circuit (Pink wire) between underhood fuse block terminal D10 and PNP switch terminal No. 11 for an open or loose terminal connections. Repair as necessary.
  18. Inspect for an open and loose terminal connections in ignition voltage circuit between underhood fuse block terminal D10 and ignition switch. Repair as necessary. If okay, replace ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT.
  19. Move gearshift lever to "R" position. Is scan tool reading REVERSE? If so, go to step  34 . If not, go to next step.
  20. Move gearshift lever to "N" position. Is scan tool reading NEUTRAL? If so, go to next step. If not, go to step  24 .
  21. Disconnect PNP switch 12-way harness connector. Using scan tool, monitor PNP switch A/B/C/P position "B". Does it read LOW? If so, go to next step. If not, go to step  23 .
  22. Replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  23. Inspect PNP switch position "B" (Yellow wire) for a short to voltage. Repair as necessary. If okay, replace TCM.
  24. Disconnect PNP switch 12-way harness connector. Jumper PNP switch 12-way harness connector terminal No. 10 (White wire) to battery voltage. Using scan tool, monitor PNP SW A/B/C/P position "P". Does it read HI?
  25. Inspect for loose terminal connections. Repair as necessary. If okay, replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  26. Inspect PNP switch position "P" (White wire) for an open and loose terminal connections. Repair as necessary. If okay, replace TCM.
  27. Move gearshift lever to "N" position. Is scan tool reading NEUTRAL? If so, go to next step. If not, go to step  31 .
  28. Disconnect PNP switch 12-way harness connector. Using scan tool, monitor PNP switch A/B/C/P position "C". Does it read LOW? If so, go to next step. If not, go to step  30 .
  29. Replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  30. Inspect PNP switch position "C" (Gray wire) for a short to voltage. Repair as necessary. If okay, replace TCM.
  31. Disconnect PNP switch 12-way harness connector. Jumper PNP switch 12-way harness connector terminal No. 8 (Yellow wire) to battery voltage. Using scan tool, monitor PNP switch A/B/C/P position "B". Does it read HI? If so, go to next step. If not, go to step  33 .
  32. Inspect for loose terminal connections. Repair as necessary. If okay, replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  33. Inspect PNP switch position "B" (Yellow wire) for an open and loose terminal connections. Repair as necessary. If okay, replace TCM.
  34. Move gearshift lever to "N" position. Is scan tool reading NEUTRAL? If so, go to next step. If not, go to step  38 .
  35. Disconnect PNP switch 12-way harness connector. Jumper PNP switch 12-way harness connector terminal No. 9 (Tan/White wire) to battery voltage. Using scan tool, monitor PNP switch A/B/C/P position "A". Does it read HI? If so, go to next step. If not, go to step  37 .
  36. Inspect for loose terminal connections. Repair as necessary. If okay, replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  37. Inspect PNP switch position "A" (Tan/White wire) for an open and loose terminal connections. Repair as necessary. If okay, replace TCM.
  38. Disconnect PNP switch 12-way harness connector. Using scan tool, monitor PNP switch A/B/C/P position "C". Does it read LOW? If so, go to next step. If not, go to step  40 .
  39. Replace PNP switch. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  40. Inspect PNP switch position "C" (Gray wire) for a short to voltage. Repair as necessary. If okay, replace TCM.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.