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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G3500, VAN PASSENGER EXTENDED, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 3 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 8.1L)DIAGNOSTIC TESTSDTC P1518: THROTTLE ACTUATOR CONTROL MODULE SERIAL DATA CIRCUITDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 F

Diagnostic Procedures

2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 FSECTION Diagnostic Procedures
WARNING: This page is about a different variant/trim than selected.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK . After performing powertrain diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. On Chevy Express and Savana, remove cover from underhood junction block, located in left rear of engine compartment. Using test light connected to ground, probe both sides of ETC fuse (15-amp). On all other models, remove cover from underhood junction block, located in left side of engine compartment, near battery. Using test light connected to ground, probe both sides of THROT CONT fuse (15-amp). On all models, if test light illuminates on at least one side of fuse, go to next step. If test light does not illuminate, diagnose ignition relay circuit. See POWER DISTRIBUTION article in WIRING DIAGRAMS.
  3. Turn ignition off. On Chevy Express and Savana, use a test light connected to ground and probe both sides of ETC fuse (15-amp). On all other models, use a test light connected to ground and probe both sides of THROT CONT fuse (15-amp). On all models, if test light illuminates on one side of fuse, go to step  22. If test light does not illuminate, go to next step.
  4. Using scan tool, monitor DTC INFO. If DTC P0606 is set with P1518, see DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 OR P1683: CONTROL MODULE FAULT . If DTC P0606 is not set with P1518, go to next step.
  5. Observe Driver Information Center (DIC) display. If DIC is displaying REDUCED ENGINE POWER, go to next step. If DIC is not displaying REDUCED ENGINE POWER, start engine. Increase engine speed to 3,000 RPM, if possible. Using scan tool, monitor DTC INFO. If DTC P1518 failed this ignition, go to next step. If DTC P1518 did not fail this ignition, see DIAGNOSTIC AIDS .
    6. NOTE: Disconnecting TAC motor harness connector may cause additional DTC(s) to set.
  6. Turn ignition off. Disconnect Black 2-pin TAC motor harness connector. Turn ignition on, with engine off. Measure voltage between ground and TAC motor harness connector terminal "A" (Brown wire) and terminal "B" (Yellow wire). If voltage reading on both circuits is greater than 8 volts, go to step  12. If voltage reading on either circuit is 8 volts or less, go to next step.
  7. Turn ignition off. Check for continuity between ground and TAC motor harness connector terminal "A" (Brown wire) and terminal "B" (Yellow wire). If continuity exists at either terminal, go to step  10. If continuity does not exist at either terminal, go to next step.
  8. Turn ignition off. On Chevy Express and Savana, remove ETC fuse (15-amp). On all other models, remove THROT CONT fuse (15-amp). On all models, check for continuity between ground and TAC motor side fuse terminal. If continuity exists, go to next step. If continuity does not exist, go to step  11.
  9. Disconnect 16-pin TAC module harness connector C1. Check for continuity between ground and TAC motor side fuse terminal. If continuity exists, repair short to ground as necessary. After repair, go to step  28. If continuity does not exist, go to step  24.
  10. Disconnect 16-pin TAC module harness connector C1. Check for continuity between ground and TAC module harness connector C1 terminals No. 8 (Brown wire) and No. 16 (Yellow wire). If continuity exists, repair short to ground as necessary. After repair, go to step  28. If continuity does not exist, go to step  24.
  11. Turn ignition off. Disconnect 16-pin TAC module harness connector C1. Check for open or high resistance in Pink wire between TAC module harness connector C1 terminal No. 7 and underhood fuse block. See Figure. Repair as necessary. After repair, go to step  28. If no problem is found, go to step  24.
  12. Turn ignition off. Disconnect 16-pin TAC module harness connector C1. Turn ignition on, with engine off. Check for short to voltage in Brown wire between TAC motor harness connector terminal "A" and TAC module harness connector C1 terminal No. 8. Check for short to voltage in Yellow wire between TAC motor harness connector terminal "B" and TAC module harness connector C1 terminal No. 16. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  13. Turn ignition off. Disconnect 10-pin TAC module harness connector C2. Check Brown wire between TAC motor harness connector terminal "A" and TAC module harness connector C1 terminal No. 8 for being shorted to any other TAC module circuit. Check Yellow wire between TAC motor harness connector terminal "B" and TAC module harness connector C1 terminal No. 16 for being shorted to any other TAC module circuit. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  14. On Chevy Express and Savana, check for open or high resistance in Tan/White wire between 16-pin TAC module harness connector C1 terminal No. 15 and ground. Ground point is located on rear of left cylinder head. On all other models, check for open or high resistance in Black/White wire between 16-pin TAC module harness connector C1 terminal No. 15 and ground. Ground point is located on left rear of engine block. On all models, repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  15. Measure voltage between ground and 16-pin TAC module harness connector C1 terminals No. 12 (Orange/Black wire) and No. 13 (Dark Blue/White wire). See Figure. If voltage reading on both serial data circuits is 0-4.5 volts, go to next step. If voltage reading on both serial data circuits is not 0-4.5 volts, go to step  18.
  16. Turn ignition off. Check for continuity between ground and 16-pin TAC module harness connector C1 terminals No. 12 (Orange/Black wire) and No. 13 (Dark Blue/White wire). If DVOM displays OL on both serial data circuits, go to step  20. If DVOM does not display OL on both serial data circuits, go to next step.
  17. Disconnect Blue 80-pin PCM harness connector C1. See COMPONENT LOCATIONS . Check for continuity between ground and 16-pin TAC module harness connector C1 terminals No. 12 (Orange/Black wire) and No. 13 (Dark Blue/White wire). If continuity exists, repair short to ground as necessary. After repair, go to step  28. If no problem is found, go to next step.
  18. Check Orange/Black wire between 16-pin TAC module harness connector C1 terminal No. 12 and Blue 80-pin PCM harness connector C1 terminal No. 14 for being shorted to any other circuit at TAC module and PCM harness connectors. Check Dark Blue/White wire between 16-pin TAC module harness connector C1 terminal No. 13 and Blue 80-pin PCM harness connector C1 terminal No. 15 for being shorted to any other circuit at TAC module and PCM harness connectors. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  19. Check for short to voltage in Orange/Black wire between 16-pin TAC module harness connector C1 terminal No. 12 and Blue 80-pin PCM harness connector C1 terminal No. 14. Check for short to voltage in Dark Blue/White wire between 16-pin TAC module harness connector C1 terminal No. 13 and Blue 80-pin PCM harness connector C1 terminal No. 15. Repair as necessary. After repair, go to step  28. If no problem is found, go to step  25.
  20. Disconnect Blue 80-pin PCM harness connector C1. See COMPONENT LOCATIONS . Check for open or high resistance in Orange/Black wire between 16-pin TAC module harness connector C1 terminal No. 12 and Blue 80-pin PCM harness connector C1 terminal No. 14. Check for open or high resistance in Dark Blue/White wire between 16-pin TAC module harness connector C1 terminal No. 13 and Blue 80-pin PCM harness connector C1 terminal No. 15. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  21. Reconnect PCM harness connectors. Turn ignition on, with engine off. Measure voltage between ground and 16-pin TAC module harness connector terminals No. 12 (Orange/Black wire) and No. 13 (Dark Blue/White wire). See Figure. If voltage reading is zero volts, go to step  25. If voltage reading is not zero volts, go to step  24.
  22. Turn ignition off. Disconnect 16-pin TAC module harness connector C1. Check for short to battery voltage in Pink wire between TAC module harness connector C1 terminal No. 7 and underhood junction block. See Figure. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  23. Turn ignition on. Check for short to voltage in Brown wire between TAC motor harness connector terminal "A" and TAC module harness connector C1 terminal No. 8. Check for short to voltage in Yellow wire between TAC motor harness connector terminal "B" and TAC module harness connector C1 terminal No. 16. Repair as necessary. After repair, go to step  28. If no problem is found, go to next step.
  24. Check for poor connection/terminal tension at TAC module harness connectors. Repair as necessary. After repair, go to step  28. If no problem is found, go to step  26.
  25. Check for poor connection/terminal tension at PCM harness connectors. Repair as necessary. After repair, go to step  28. If no problem is found, go to step  27.
  26. Replace TAC module. After repair, go to step  28.
  27. Replace and program PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step.
  28. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within conditions for running the DTC as specified in CODE ENABLE CRITERIA . If DTC does not reset, go to next step. If DTC resets, go to step  2.
  29. Using scan tool, check for any other DTCs that are present. If no other DTCs are present, repair is complete. If any other DTCs are present, repair DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
RENDER: 1.0x

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

  • • You smell fuel, burning insulation, or see smoke.
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  • • 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.