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Home >> GMC >> 1996 >> Forward Control 5.7 K, L05, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Engine Testing - P Series (Gasoline) >> On-Board Diagnostic (OBD) System Check >> A-2, No Scan Tool Data
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A-2, No Scan Tool Data

  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Turn ignition off for 30 seconds. Turn ignition on with engine off. Observe MIL. If MIL illuminates, go to next step. If MIL does not illuminate, see A-1, MALFUNCTION INDICATOR LIGHT (MIL) .
  3. Install scan tool. If scan tool communicates with VCM, system is okay. If scan tool does not communicate with VCM, go to next step.
  4. Disconnect scan tool. Using DVOM, check voltage between ground DLC terminal No. 2. DVOM should read 5 volts. If voltage is greater than 5 volts, go to step 16). If voltage is 5 volts or less, go to next step.
  5. Connect a test light to ground. Using test light, probe DLC terminal No. 16. See Figure. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  6. Connect test light to battery voltage. Using test light, probe DLC terminals No. 4 and 5. If test light illuminates on both circuits, go to next step. If test light does not illuminate on either circuit, go to step 12).
  7. Check cigarette lighter for power. If power is present at cigarette lighter, go to next step. If power is not present at cigarette lighter, go to step 13).
  8. Install and check scan tool on another vehicle. If scan tool works, go to next step. If scan tool does not work, go to step 14).
  9. Turn ignition off. Using DVOM, check resistance between ground and DLC terminal No. 2. Resistance should be 10 ohms. If resistance is less than 10 ohms, go to step 15). If resistance is 10 ohms or greater, go to step 18).
  10. Disconnect Black VCM connector. Using DVOM, check resistance between ground and DLC terminal No. 2. Resistance should be 10 ohms. If resistance is less than 10 ohms, go to step 15). If resistance is 10 ohms or greater, go to step 18).
  11. Check fuse No. 7 (AUX PWR). If fuse is faulty, repair short to ground in DLC terminal No. 16 circuit (Orange wire). If fuse is okay, repair open in DLC terminal No. 16 circuit (Orange wire). After repairs, go to step 19).
  12. Repair open in affected circuit. After repairs, go to step 19).
  13. Repair cigarette lighter circuit. After repairs, go to step 19).
  14. Repair or replace faulty scan tool and/or cables. After repairs, go to step 19).
  15. Repair short to ground in serial data line (Purple wire). See Figure. After repairs, go to step 19).
  16. Disconnect Black VCM connector. Recheck voltage at DLC terminal No. 2. If voltage is greater than 5 volts, go to next step. If voltage is less than 5 volts, go to step 18).
  17. Repair short to voltage in serial data line (Purple wire). After repairs, go to step 19).
  18. Check for open in serial data line. If circuit is okay, check VCM and DLC connectors. If connectors are okay, replace VCM. Perform VCM relearn procedures. After repairs, go to next step.
  19. Using scan tool, select DTC, CLEAR INFO function. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start or starts and dies/stalls, go to step 2).
  20. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) are stored, diagnose DTC. See TESTS W/CODES article. If DTC(s) are not present, go to next step.
  21. Select CAPTURE INFO, REVIEW INFO function. If additional DTC(s) are displayed, diagnose DTC. See TESTS W/CODES article.
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